1

An Overview of Technologies for Geophysical Vector MagneticSurvey: A Case Study of the Instrumentation and Future Directions

Huan Liu1,2,3, Member, IEEE, Haobin Dong1,2, Jian Ge1,2, and Zheng Liu3, Senior Member, IEEE

1School of Automation, China University of Geosciences, Wuhan Hubei, 430074, China2Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan Hubei, 430074, China

3School of Engineering, University of British Columbia Okanagan, Kelowna BC, V1V 1V7, Canada

Magnetic survey techniques have been used in many years in an attempt to better evaluate the likelihood of recoverable hydrocarbonreservoirs by determining the depth and pattern of sedimentary rock formations containing magnetic minerals, such as magnetite.Utilizing airplanes, large area magnetic surveys have been conducted to estimate, for example, the depth to igneous rock and thethickness of sedimentary rock formations. In this case, the vector magnetic survey method can simultaneously obtain the modulusand direction information of the Earth’s magnetic field, which can effectively reduce the multiplicity on data inversion, contributeto the quantitative interpretation of the magnetic body and obtain more precise information and characteristics of magnetic fieldresource, so as to improve the detection resolution and positioning accuracy of the underground target body. This paper presentsa state-of-the-art review of the application situations, the technical features, and the development of the instruments for differentapplication scenarios, i.e., ground, wells, marine, airborne, and satellites, respectively. The potential of multi-survey technique fusionfor magnetic field detection is also discussed.

Index Terms—Magnetic survey technique, geophysical exploration, instrumentation, magnetometer, geomagnetic

I. INTRODUCTION

M agnetic survey techniques are one of the most effectivemethods for geophysical engineering and environmen-

tal exploration [1]–[4], e.g., unexploded ordnance (UXO)detection [5]–[7], mineral exploration [8]–[11], etc [12]–[17].In recent years, the vector magnetic survey techniques havedeveloped rapidly. When compared it with the traditionalscalar magnetic survey methods [18]–[21], the vector magneticsurvey can simultaneously obtain the modulus and directioninformation of the Earth’s magnetic field, which can effectivelyreduce the multiplicity on data inversion [22]–[24]. Further, itcan contribute to the quantitative interpretation of the magneticbody and obtain more precise information and characteristicsof magnetic field resource, and thus improve the detectionresolution and positioning accuracy of the underground targetbody [25]–[27].

The vector magnetic survey technique can be mainly dividedinto ground magnetic survey, wells magnetic survey, marinemagnetic survey, airborne magnetic survey, and satellites mag-netic survey, and each technique has its own characteristics.The ground magnetic survey is mainly used for the detectionof ore bodies distributed horizontally on the surface [28].However, due to the abnormal superposition of different ge-ological bodies on the surface, it is difficult to distinguishthe depth. Hence, it is often combined with other magneticsurvey techniques [29]. The wells magnetic survey is basedon the magnetic characteristics of rock ore, measuring threeorthogonal components of the geomagnetic field, and theradial detection range is large [30]. Further, this techniquecan be employed to find both strong magnetite deposits and

Corresponding author: Haobin Dong (email: donghb@cug.edu.cn).

non-ferrous metals with weaker magnetic intensities, and itis an effective method for detecting magnetic ore bodies,especially, provides a scientific basis for the exploration andevaluation of mineral resources in the deep earth [31]. Themarine magnetic survey always adopts a ship equipped withmagnetometers to conduct geomagnetic surveys in the oceanarea. It plays a crucial role in the detection of military targetssuch as underwater submarines, unexploded weapons, andmagnetic obstacles [32]. The traditional approach is mainlybased on total field measurement. In recent years, the three-component or full-tensor magnetic gradient based marinemagnetic survey technique has been employed to obtain moregeomagnetic information to provide important parameters forthe naval battlefield [33]. The airborne magnetic survey isappropriate for scanning large areas during reconnaissanceto delimit target areas for detailed ground surveys duringthe prospecting stage [34]. In particular, it can be used incoalfield studies to map out a broad structural frameworkover an exploration area with complex terrain both quicklyand effectively [35]. The satellite magnetic survey can obtainhigh-quality, global coverage magnetic survey data, conductall-weather and uninterrupted measurements, and thus carryout a series of scientific researches such as the evolution of thegeomagnetic field and the law of space current movement [36],[37].

In this paper, according to different application scenarios,first, the technical characteristics of the vector magnetic mea-surement compared with the scalar magnetic measurement aresummarized. Second, we elaborate on the application situa-tions, the technical features, and the instruments developmentof the ground vector magnetic survey technique, the wellsvector magnetic survey technique, the marine vector magnetic

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Prepared for submission to JINST

Measurements with silicon detectors at extreme neutronfluences

I. Mandić,a,1 V. Cindro,a A. Gorišek,a B. Hiti,a G. Kramberger,a M. Mikuž,a,b M. Zavrtanik,a P.Skomina,a S. Hidalgo,c G. Pellegrinic

aJožef Stefan Institute, Ljubljana, SloveniabDepartment of Physics, University of Ljubljana, SloveniabCNM-IMB-CSIC, Barcelona, Spain

E-mail: igor.mandic@ijs.si

Abstract: Thin pad detectors made from 75 µm thick epitaxial silicon on low resistivity substratewere irradiated with reactor neutrons to fluences from 2.5×1016 n/cm2 to 1×1017 n/cm2. Edge-TCTmeasurements showed that the active detector thickness is limited to the epitaxial layer and doesnot extend into the low resistivity substrate even after the highest fluence. Detector current wasmeasured under reverse and forward bias. The forward current was higher than the reverse at thesame voltage but the difference gets smaller with increasing fluence. Rapid increase of current(breakdown) above 700 V under reverse bias was observed. An annealing study at 60C was madeto 1200 minutes of accumulated annealing time. It showed that the reverse current anneals withsimilar time constants as measured at lower fluences. A small increase of forward current due toannealing was seen. Collected charge was measured with electrons from 90Sr source in forwardand reverse bias configurations. Under reverse bias the collected charge increased linearly withbias voltage up to 6000 electrons at 2.5×1016 n/cm2 and 3000 electrons at 1×1017 n/cm2. Rapidincrease of noise was measured above ∼ 700 V reverse bias due to breakdown resulting in worseS/N ratio. At low bias voltages slightly more charge is measured under forward bias compared toreverse. However better S/N is achieved under reverse bias. Effective trapping times were estimatedfrom charge collection measurements under forward bias showing that at high fluences they aremuch longer than values extrapolated from low fluence measurements - at 1×1017 n/cm2 a factor of6 larger value was measured.

Keywords: Silicon detectors, Extreme radiation levels

1Corresponding author.

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This is a pre-print of an article.

Point-to-Point Stabilised Optical Frequency Transfer withActive Optics

Benjamin P. Dix-Matthews1,2, Sascha W. Schediwy1,2, David R. Gozzard1,2,

Etienne Savalle3, Francois-Xavier Esnault4, Thomas Leveque4, Charles Gravestock1,

Darlene D’Mello1, Skevos Karpathakis1, Michael Tobar2, Peter Wolf3

Compiled on: July 13, 2020

Abstract Timescale comparison between optical atomic

clocks over ground-to-space and terrestrial free-spacelaser links will have enormous benefits for fundamental

and applied science, from measurements of fundamental

constants and searches for dark matter, to geophysics

and environmental monitoring. However, turbulence in

the atmosphere creates phase noise on the laser signal,

greatly degrading the precision of the measurements,

and also induces scintillation and beam wander which

cause periodic deep fades and loss of signal. We demon-

strate phase stabilized optical frequency transfer over a

265 m horizontal point-to-point free-space link between

optical terminals with active tip-tilt mirrors to suppress

beam wander, in a compact, human-portable set-up. A

phase stabilized 715 m underground optical fiber link

between the two terminals is used to measure the perfor-

mance of the free-space link. The active optics terminals

enabled continuous, coherent transmission over peri-

ods of up to an hour. We achieve an 80 dB suppression

of atmospheric phase noise to 3× 10−6 rad2 Hz−1 at

1 Hz, and an ultimate fractional frequency stability of

1.6× 10−19 after 40 s of integration. At high frequency

this performance is limited by the residual atmospheric

Benjamin P. Dix-Matthewsbenjamin.dix-matthews@research.uwa.edu.au

1 International Centre for Radio Astronomy Research, TheUniversity of Western Australia, Perth, Australia

2 Australian Research Council Centre of Excellence for En-gineered Quantum Systems, The University of WesternAustralia, Perth, Australia

3 SYRTE, Observatoire de Paris, Universite PSL, CNRS,Sorbonne Universite, LNE, Paris, France

4 Centre National d’Etudes Spatiales (CNES), Toulouse,France

noise after compensation and the frequency noise of the

laser seen through the unequal delays of the free spaceand fiber links. Our long term stability is limited by

the thermal shielding of the phase stabilization system.

We achieve residual instabilities below those of the best

optical atomic clocks, ensuring clock-limited frequency

comparison over turbulent free-space links.

Keywords phase stabilization, free-space laser links,

metrology

1 Introduction

Modern optical atomic clocks have the potential to rev-

olutionise high-precision measurements in fundamental

and applied sciences [1–7]. The ability to realise remotetimescale comparison in situations where fiber links are

impractical or impossible, specifically, between ground-

and space-based optical atomic clocks [8–22], will enable

significant advances in fundamental physics and prac-

tical applications including tests of the variability of

fundamental constants [23,24], general relativity [25,26],

searches for dark matter [27], geodesy [28–34], and global

navigation satellite systems [35] amongst others [36–46].

These efforts lead on from optical timing links developed

for timescale comparison between microwave atomic

clocks [47–49], and efforts are underway to develop op-

tical clocks that can be deployed on the International

Space Station [50] and on dedicated spacecraft [51].

Similarly, timescale comparisons between mobile ter-

restrial optical clocks [1, 52–55], where one or more

mobile clocks are able to be deployed and moved over

an area of interest, enable ground tests of general rela-

tivity and local geopotential measurements for research

in geophysics, environmental monitoring, surveying and

resource exploration.

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Absolute neutrino mass as the missing link to the dark sector

Thede de Boera, Michael Klasena, Caroline Rodenbeckb, and Sybrand Zeinstraaa Institut fur Theoretische Physik, Westfalische Wilhelms-Universitat Munster,

Wilhelm-Klemm-Straße 9, 48149 Munster, Germany andb Institut fur Kernphysik, Westfalische Wilhelms-Universitat Munster,

Wilhelm-Klemm-Straße 9, 48149 Munster, Germany

With the KATRIN experiment, the determination of the absolute neutrino mass scale down tocosmologically favored values has come into reach. We show that this measurement provides themissing link between the Standard Model and the dark sector in scotogenic models, where thesuppression of the neutrino masses is economically explained by their only indirect coupling to theHiggs field. We determine the linear relation between the electron neutrino mass and the scalarcoupling λ5 associated with the dark neutral scalar mass splitting to be λ5 = 3.1 × 10−9 mνe/eV.This relation then induces correlations among the DM and new scalar masses and their Yukawacouplings. Together, KATRIN and future lepton flavor violation experiments can then probe thefermion DM parameter space, irrespective of the neutrino mass hierarchy and CP phase.

INTRODUCTION

MS-TP-20-28

The identification of cold Dark Matter (DM) – a myste-rious particle that according to most cosmological modelsis five times more abundant in the Universe than ordi-nary matter – is one of the most urgent challenges inmodern physics. Neutrinos as only weakly interactingmassive particles in the Standard Model (SM) have theright characteristics of a DM candidate, but are neithercold nor can they, due to their tiny masses, contributemore than a small fraction (between 0.5 and 1.6%) to themeasured total DM relic density [1, 2]. Nevertheless theidea that neutrinos and DM might be related is intrigu-ing and has led to an enormous theoretical activity onso-called radiative seesaw models, where the suppressionof the SM neutrino masses is due to their only indirectinteraction (via DM) with the SM Higgs field [3–5].

While the fact that at least two of the three neutrinoflavors are massive has been deduced about 20 years agofrom atmospheric [6] and solar [7, 8] neutrino oscillations,their absolute masses are still unknown. The KATRINexperiment has recently improved the upper limit on theelectron (anti)neutrino mass to 1.1 eV [9] and ultimatelyaims at a sensitivity of 0.2 eV [10]. This value would rivalthe cosmological constraint on the sum of the SM neu-trino masses of

∑imνi < 0.12 eV, assuming the ΛCDM

model and normal hierarchy (NH), the minimal value al-lowed by oscillation experiments being 0.06 eV [11]. Aninverted hierarchy (IH) is still a possiblity, although thelong-baseline experiments T2K and NOνA and furtherevidence from reactor and atmospheric neutrinos favorNH. For the CP phase, T2K and to a lesser degree alsoNOνA data seem to favor 3π/2 (π/2) for NH (IH) [12].

In radiative seesaw models, the SM neutrinos ν, evenunder a discrete Z2 symmetry, interact with the (also Z2-even) SM Higgs field φ and obtain their masses via a dark(Z2-odd) sector, which contains only a small number ofnew multiplets (typically up to four new scalar/fermionsinglets, doublets or triplets under SU(2)L) [4]. In Ma’s

S. Fraser et al. / Physics Letters B 737 (2014) 280–282 281

Fig. 2. One-loop generation of seesaw neutrino mass with heavy Majorana N .

a different mass hierarchy. If m1, m2 ! mN and m21/mN ! mS !

m1, then a lopsided seesaw [14] occurs with m! " #m22/mN as

in the canonical seesaw, but ! # S mixing may be significant, i.e. m1m2/mSmN , whereas ! # N mixing is the same as in the canon-ical seesaw, i.e.

$m!/mN . In the inverse seesaw, ! # N mixing

is even smaller, i.e. m!/m2, but ! # S mixing is much larger, i.e. m2/m1, which is only bounded at present by about 0.03 [15]. In the double seesaw, the effective mass of N is m2

1/mS , so ! # Nmixing is also

$m!/mN . Here mS % mN , so the ! # S mixing is

further suppressed by m1/mS .In the original scotogenic model [7], neutrino mass is radia-

tively induced by heavy neutral Majorana singlet fermions N1,2,3 as shown in Fig. 2. However, they may be replaced by Dirac fermions. In that case, a U (1)D symmetry may be defined [16], under which "1,2 transform oppositely. If Z2 symmetry is retained, then a radia-tive inverse seesaw neutrino mass is also possible [17,18]. We dis-cuss here instead the new mechanism of Fig. 1, based on the third one-loop realization of neutrino mass first presented in Ref. [2]. The smallness of mN , i.e. the Majorana mass of NL , may be natu-rally connected to the violation of lepton number by two units, as in the original inverse seesaw proposal using Eq. (1). It may also be a two-loop effect as first proposed in Ref. [19], with a number of subsequent papers by other authors, including Refs. [20–22].

In our model, lepton number is carried by (E0, E#)L,R as well as NL . This means that the Yukawa term NL(E0

R#0 # E#R #+) is

allowed, but not NL(E0L#

0 # E#L #+). In the 3 &3 mass matrix span-

ning (E0R , E0

L , NL), i.e.

ME,N =

!

"0 mE mD

mE 0 0

mD 0 mN

#

$ , (3)

mE comes from the invariant mass term (E0R E0

L + E+R E#

L ), mD comes from the Yukawa term given above connecting NL with E0

R through '#0( = v , and mN is the soft lepton-number breaking Majorana mass of NL . Assuming that mN ! mD , mE , the mass eigenvalues of ME,N are

m1 = m2EmN

m2E + m2

D

, (4)

m2 =%

m2E + m2

D + m2DmN

2(m2E + m2

D), (5)

m3 = #%

m2E + m2

D + m2DmN

2(m2E + m2

D). (6)

In the limit mN ) 0, E0R pairs up with E0

L cos $ + NL sin $ to form a Dirac fermion of mass

%m2

E + m2D , where sin $ = mD/

%m2

E + m2D .

This means that the one-loop integral of Fig. 1 is well approxi-mated by

m! = f 2m2DmN

16%2(m2E + m2

D # m2s )

&1 # m2

s ln((m2E + m2

D)/m2s )

(m2E + m2

D # m2s )

'. (7)

This expression is indeed of the form expected of the inverse see-saw.

The radiative mechanism of Fig. 1 is also suitable for supporting a discrete flavor symmetry, such as Z3. Consider the choice

(!i, li)L * 1,1+,1++, s1 * 1,

(s2 + is3)/$

2 * 1+, (s2 # is3)/$

2 * 1++, (8)

with mass terms m2s s2

1 + m+ 2s (s2

2 + s23), then the induced 3 & 3 neu-

trino mass matrix is of the form

M! =

!

"fe 0 0

0 fµ 0

0 0 f&

#

$

!

"I(m2

s ) 0 0

0 0 I(m+ 2s )

0 I(m+ 2s ) 0

#

$

&

!

"fe 0 0

0 fµ 0

0 0 f&

#

$

=

!

"f 2e I(m2

s ) 0 0

0 0 fµ f& I(m+ 2s )

0 fµ f& I(m+ 2s ) 0

#

$ , (9)

where I is given by Eq. (7) with f 2 removed. Let liR * 1, 1+, 1++ , then the charged-lepton mass matrix is diagonal using just the one Higgs doublet of the standard model, in keeping with the recent discovery [23,24] of the 125 GeV particle. To obtain a realistic neu-trino mass matrix, we break Z3 softly, i.e. with an arbitrary 3 & 3mass-squared matrix spanning s1,2,3, which leads to!

"1 0 0

0 1/$

2 i/$

2

0 1/$

2 #i/$

2

#

$ O T

!

("

I(m2s1) 0 0

0 I(m2s2) 0

0 0 I(m2s3)

#

)$

& O

!

"1 0 0

0 1/$

2 1/$

2

0 i/$

2 #i/$

2

#

$ , (10)

where O is an orthogonal matrix but not the identity, and there can be three different mass eigenvalues ms1,s2,s3 for the s1,2,3 sec-tor. The assumption of Eq. (8) results in Eq. (10) and allows the following interesting pattern for the neutrino mass matrix M! . The Yukawa couplings fe,µ,& may be rendered real by absorbing their phases into the arbitrary relative phases between E0

R and !e,µ,& . If we further assume fµ = f& , then M! is of the form [25]

M! =

!

"A C C,

C D, B

C, B D

#

$ , (11)

where A and B are real. Note that this pattern is protected by a symmetry first pointed out in Ref. [26], i.e. e ) e and µ # & exchange with CP conjugation, and appeared previously in Refs. [27,28]. As such, it is also guaranteed to yield maxi-mal !µ # !& mixing ($23 = %/4) and maximal CP violation, i.e. exp(#i') = ±i, whereas $13 may be nonzero and arbitrary. Our scheme is thus a natural framework for this possibility. Further, from Eq. (7), it is clear that it is also a natural framework for quasi-degenerate neutrino masses as well. Let

F (x) = 11 # x

&1 + x ln x

1 # x

', (12)

where x = m2s /(m

2E + m2

D), then Eq. (7) becomes

m! = f 2m2DmN

(m2E + m2

D)F (x). (13)

FIG. 1. Neutrino mass generation in scotogenic models.

famous scotogenic model (see Fig. 1), only one additionalscalar doublet η and (for three massive SM neutrinos)three generations of fermion singlets Ni (sterile neutrinoswith i = 1, 2, 3) are required [3]. The parameter spaceis therefore much smaller than, e.g., the one of super-symmetry and can be better constrained with neutrinooscillation data via the Casas-Ibarra method [13], limitson lepton flavor violation (LFV) [14], and measurementsof the DM relic density [15]. Nevertheless, these previ-ous analyses found that the dark scalar/fermion massesas well as their scalar and Yukawa couplings could stillvary over several orders of magnitude.

In this Letter, we demonstrate that a determination ofthe absolute electron neutrino mass, which has now comeinto reach, will provide additional stringent constraintson the dark sector of the scotogenic model in a way thatis almost independent of the neutrino hierarchy and CPphase. In particular, we determine the linear relation be-tween the absolute electron neutrino mass and the scalarcoupling associated with the mass splitting of the darkneutral scalars. This linear dependence induces corre-lations among the other parameters of the model, i.e.the DM and scalar masses and their Yukawa couplings,which we can also quantify. Together, current neutrinomass and future LFV experiments can then probe almostthe entire fermion DM parameter space.

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Eur. Phys. J. A manuscript No.(will be inserted by the editor)

On the nature of near-threshold bound and virtual states

Inka Matuschek1, Vadim Baru2,3,4, Feng-Kun Guo5,6, Christoph Hanhart1

1Forschungszentrum Julich, Institute for Advanced Simulation, Institut fur Kernphysik and Julich Center for Hadron Physics, D-52425 Julich,Germany2Helmholtz-Institut fur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universitat Bonn, D-53115 Bonn, Germany3Institute for Theoretical and Experimental Physics NRC (Kurchatov Institute), Moscow 117218, Russia4P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991, Leninskiy Prospect 53, Moscow, Russia5CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China6School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China

Abstract Physical states are characterised uniquely by theirpole positions and the corresponding residues. Accordingly,in those parameters also the nature of the states should beencoded. For bound states (poles on the real s-axis belowthe lowest threshold on the physical sheet) there is an es-tablished criterion formulated originally by Weinberg in the1960s, which allows one to estimate the amount of com-pact and molecular components in a given state. We demon-strate in this paper that this criterion can be straightforwardlyextended to shallow virtual states (poles on the real s-axisbelow the lowest threshold on the unphysical sheet) whichshould be classified as molecular. We argue that predomi-nantly non-molecular or compact states exist either as boundstates or as resonances (poles on the unphysical sheet off thereal energy axis) but not as virtual states. We also discuss thelimitations of the mentioned classification scheme.

1 Introduction

The observations of the D∗s0(2317) [1], which is slightlybelow the DK threshold, and the charmonium-like mesonX(3872) in 2003 [2], which lies remarkably close to theD0D∗0 threshold, sparked a renewed interest in heavymeson spectroscopy, since their properties are in conflictwith the predictions of the quark model. Since then a largenumber of exotic hadrons which cannot be accommodatedby conventional quark models, were discovered and arestill being found in such facilities as BaBar, Belle, BESIIIand LHCb. Those in the heavy quarkonium mass regionare called XY Z states. Various models were developedfor describing these exotic states. The proposals includehadro-quarkonia, hybrids, tetraquarks, molecular states andkinematical effects, for recent reviews see, for example,

Refs. [3–10]. All these states have in common, that theirmasses are located above the first heavy-quark open-flavorthreshold, DD or BB, respectively. Moreover, many masseslie close to some open-flavor threshold, which makes thesestates natural candidates for hadronic molecules.

Unrevealing the nature of the XY Z states is of high in-terest for it will shed light on how quantum chromodynam-ics (QCD) forms hadrons. To form the basis for this quest,one needs to provide theoretically sound definitions of thedifferent structures. In the 1960’s Weinberg found a way todiscriminate between composite (or molecular) and elemen-tary (or compact) near-threshold states in the weak-bindinglimit [11–13]. In particular, he showed that the composite-ness is given by 1−Z, where Z is the field renormalizationconstant of a state. Moreover, he derived that the residue atthe pole in the scattering amplitude of two hadrons, whichcan couple to this state, directly measures Z and obtained re-lations between Z, the scattering length a and the effectiverange r. Then, he applied this model-independent scheme tothe deuteron and demonstrated that the deuteron indeed is notan elementary particle.

The derivation of the mentioned compositeness criterionrelies on the normalization of the wave function. Accord-ingly, it is formally applicable only to bound states. In recentyears, however, much research has been devoted to a possi-ble generalization of this approach, e.g. the generalization tocoupled channels was done in Ref. [14]. Of special interestis a consistent definition of the compositeness for states cor-responding to poles on the unphysical sheet, i.e., resonancesand virtual states. Related studies can be found in Refs. [15–30]. Most of these works, however, focus on resonances andcannot be applied to virtual states.

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QQss tetraquarks in the chiral quark model

Gang Yang,1, ∗ Jialun Ping,2, † and Jorge Segovia3, ‡

1Department of Physics, Zhejiang Normal University, Jinhua 321004, China2Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems,

Nanjing Normal University, Nanjing 210023, P. R. China3Departamento de Sistemas Fısicos, Quımicos y Naturales,

Universidad Pablo de Olavide, E-41013 Sevilla, Spain

The low-lying S-wave QQss (Q = c, b) tetraquark states with IJP = 00+, 01+ and 02+ aresystematically investigated in the framework of complex scaling range of chiral quark model. Everystructure including meson-meson, diquark-antidiquark and K-type configurations, and all possiblecolor channels in four-body sector are considered by means of a commonly extended variational ap-proach, Gaussian expansion method. Several narrow and wide resonance states are obtained for ccssand bbss tetraquarks with IJP = 00+ and 02+. Meanwhile, narrow resonances for cbss tetraquarksare also found in IJP = 00+, 01+ and 02+ states. These results confirm the possibility of findinghadronic molecules with masses ∼ 0.6 GeV above the noninteracting hadron-hadron thresholds.

I. INTRODUCTION

We are witnessing in the last two decades of a bigexperimental effort for understanding the heavy-flavorquark sectors of both meson and baryon systems. Manyexperiments have been settled worldwide such as B-factories (BaBar, Belle, and CLEO), τ -charm facilities(CLEO-c and BES) and hadron-hadron colliders (CDF,D0, LHCb, ATLAS, and CMS) providing a sustainedprogress in the field with new measurements of conven-tional and exotic heavy-flavored hadrons.

Within the baryon sector, and attending mostly to thespectrum, five excited Ωc baryons were announced threeyears ago by the LHCb collaboration in the Ξ+

c K− mass

spectrum [1] and, very recently, the same collaborationhas reported additional four narrow excited states of theΩb system in the Ξ0

bK− mass spectrum [2]. In 2019, two

excited bottom baryons, Λ0b(6146) and Λ0

b(6152), werediscovered in the LHCb experiment [3]. Later on, theLHCb collaboration also announced one more Λ0

b baryonaround 6070 MeV in the Λ0

bπ+π− invariant mass spec-

trum [4], which is consistent with the reported one ofthe CMS collaboration [5]. Additionally, three excitedΞ0c states were announced by the LHCb collaboration in

the Λ+c K− mass spectrum [6].

All of these newly discovered baryons undoubtedlycomplement the scarce data on heavy flavor baryons inthe Review of Particle Physics (RPP) of the ParticleData Group [7]. Furthermore, these experimental find-ings trigger a large number of theoretical investigations.The three-quark structure of the new Ωc baryons hasbeen claimed by QCD sum rules [8] and different po-tential models [9–11]. Also, the description of the Ωbsignals as P -wave conventional baryons is preferred byphenomenological quark model approach [12, 13], heavy

∗ yanggang@zjnu.edu.cn† jlping@njnu.edu.cn‡ jsegovia@upo.es

quark effective theory [14] and QCD sum rules [15].Meanwhile, the baryon-meson molecular interpretationhas been suggested for the excited Ωb baryons in Ref. [16].The Λ0

b(6072), Λ0b(6146) and Λ0

b(6152) have been identi-fied as radial and angular excitations within QCD sumrules [17–20] and chiral quark models [21, 22]. However,the DΛ − DΣ molecular configurations have been alsosuggested for these states in Ref. [23].

Apart from conventional heavy flavored baryons, thereare limited results on open-bottom mesons and detailedstudies of the open-charm ones were not undertaken untillarge datasets were obtained by CLEO at discrete energypoints and by the B-factory experiments using radiativereturns to obtain a continuous exposure of the mass re-gion. The picture that has emerged is complex due to themany thresholds in the region. This resembles the exper-imental situation found in the heavy quarkonium spec-trum with the observation of more than two dozens of un-conventional charmonium- and bottomonium-like states,the so-called XYZ mesons. However, still successful ob-servations of 6 new conventional heavy quarkonium states(4 cc and 2 bb) have been made.

Exotic states such as tetraquarks and pentaquarkshave lastly received considerable attention within thehadron physics community. Related with the first struc-tures, the best known is the X(3872), which was ob-served in 2003 as an extremely narrow peak in theB+ → K+(π+π−J/ψ) channel and at exactly the D0D∗0

threshold [24, 25], and it is suspected to be a cncn(n = u or d quark) tetraquark state whose features resem-ble those of a molecule, but some experimental findingsforbid to discard a more compact, diquark-antidiquark,component or even some cc trace in its wave function. Onthe other hand, there are no doubts of the tetraquarkcharacter of the Zc’s [26, 27] and Zb’s [28, 29] statesdue to its non-zero charge. The most prominent exam-ples of the second mentioned structures are the hidden-charm pentaquarks P+

c (4312), P+c (4380), P+

c (4440) andP+c (4457) reported in 2015 and 2019 by the LHCb col-

laboration in the Λ0b decay, Λ0

b → J/ψK−p [30, 31].The discussion about the nature of these exotic sig-

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Lepton universality and lepton flavor conservation tests with dineutrino modes

Rigo Bause,∗ Hector Gisbert,† Marcel Golz,‡ and Gudrun Hiller§

Fakultat fur Physik, TU Dortmund, Otto-Hahn-Str. 4, D-44221 Dortmund, Germany

SU(2)L-invariance links charged dilepton and dineutrino couplings. This relation allows to per-form tests of lepton universality (LU) and charged lepton flavor conservation (cLFC) with flavor-summed dineutrino observables, assuming only standard model (SM)-like light neutrinos. We obtainmodel-independent upper limits on |∆c| = |∆u| = 1 branching ratios, for D → P νν, D → PP ′ νν,P, P ′ = π,K, baryonic Λ+

c → p νν, and Ξ+c → Σ+ νν and inclusive decays, the largest of which do

not exceed few×10−5, and 10−5 if cLFC holds, and 10−6 if LU is intact.

Introduction.— Approximate symmetries of the standardmodel (SM) provide powerful means to search for newphysics (NP). In this letter we exploit the SU(2)L-linkbetween left-handed charged lepton and neutrino cou-plings and propose to use it to put quantitatively leptonuniversality (LU) and charged lepton flavor conservation(cLFC) to the test with flavor-summed dineutrino ob-servables routed in the relation (2). The latter is inde-pendent of the neutrino mixing matrix and holds for NPcontributions from above the weak scale.We give the relation (2) aiming at application to |∆c| =|∆u| = 1 processes but emphasize that it holds anal-ogously for other flavor changing or conserving quarktransitions, both up- and down-sector ones. The situ-ation, however, for c → u νν transitions is quite uniqueas the SM amplitude is entirely negligible due to an ef-ficient Glashow-Iliopoulos-Maiani (GIM)-suppression [1]and the current lack of experimental constraints 1.Tests of lepton flavor structure with c → u νν modesare a new result of this work. While the connection be-tween flavor violation and dineutrino branching ratioshas been discussed for kaons [3] and B-decays, e.g. [4],(2) is new; it explicitly relates dilepton Wilson coeffi-cients and dineutrino branching ratios to enable quanti-tative data-driven predictions, which can shed light ontodays flavor anomalies posing a challenge to LU.Model-independent relation and lepton flavor.— Con-sider the SU(2)L×U(1)Y -invariant effective theory withsemileptonic (axial-) vector four-fermion operators in-duced by NP at a scale sufficiently separated from theweak scale v = (

√2GF )

−1/2 ≃ 246GeV at lowest or-der [5]

Leff ⊃C

(1)ℓq

v2QγµQ LγµL+

C(3)ℓq

v2Qγµτ

aQ LγµτaL

+Cℓu

v2UγµU LγµL+

Cℓd

v2DγµD LγµL .

(1)

∗Electronic address: rigo.bause@tu-dortmund.de†Electronic address: hector.gisbert@tu-dortmund.de‡Electronic address: marcel.golz@tu-dortmund.de§Electronic address: ghiller@physik.uni-dortmund.de1 The D0 → νν branching ratio induced by (axial-)vector opera-tors is helicity suppressed by two powers of neutrino mass, andnegligible. The Belle result B(D0 → νν) < 9.4 · 10−5 at 90%CL [2] can therefore be safely avoided.

Here, τa are Pauli-matrices, Q and L denote left-handedquark and lepton SU(2)L-doublets and U,D stand forright-handed up-singlet, down-singlet quarks, respec-tively, with flavor indices suppressed for brevity. Nofurther dimension six four-fermion operators exist thatcontribute at lowest order to dineutrino modes assumingonly SM-like light neutrinos. Operators with quarks orleptons with two Higgs fields Φ and a covariant derivativeDµ, QγµQΦ†DµΦ, Qγµτ

aQΦ†DµτaΦ, UγµUΦ†DµΦ,DγµDΦ†DµΦ and LγµLΦ

†DµΦ, LγµτaLΦ†DµτaΦ in-

duce modified Z-couplings which give tree level contri-butions to dineutrino modes – the lepton ones conservequark flavor, the quark ones obey LU, mixed ones are ofhigher order in Leff . These operators are constrained byelectroweak and top observables, or mixing [6, 7] and arenegligible for the purpose of this work. The (axial-)vectoroperators (1), which are invariant under QCD-evolution[8], therefore provide a model-independent basis. Elec-troweak renormalization group running can be neglectedin view of the precision aimed at with this study.Writing the operators (1) in SU(2)L-components one canread off couplings to dineutrinos (CP

A ) and to chargeddileptons (KP

A ), where P = U (P = D) refers to the up-quark sector (down-quark sector) and A = L(R) denotesleft- (right-) handed quark currents

CUL = KD

L = C(1)ℓq + C

(3)ℓq , CU

R = KUR = Cℓu ,

CDL = KU

L = C(1)ℓq − C

(3)ℓq , CD

R = KDR = Cℓd .

Model-independently holds CPR = KP

R . While CPL is not

fixed in general by KPL due to the different relative signs

between C(1)ℓq and C

(3)ℓq , CU

L is related to KDL and CD

L to

KUL . We exploit this SU(2)L-link for charm physics.

Going to mass eigenstates Qα = (uLα, VαβdLβ), Li =(νLi,W

∗kiℓLk) with the Cabibbo-Kobayashi-Maskawa

(CKM) and Pontecorvo-Maki-Nakagawa-Sakata (PMNS)matrices V and W , respectively, and summing lepton fla-vors i, j incoherently, we obtain the trace identity

∑

ν=i,j

(

|CUijL

∣

∣

2+ |CUij

R

∣

∣

2)

= Tr[

CUL CU†

L + CUR CU†

R

]

=Tr[

KDLKD†

L +KURKU†

R

]

+O(λ) (2)

=∑

ℓ=i,j

(

|KDijL

∣

∣

2+ |KUij

R

∣

∣

2)

+O(λ) ,

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MNRAS 000, 1–21 (2020) Preprint 13 July 2020 Compiled using MNRAS LATEX style file v3.0

Core-collapse supernova neutrino emission and detection

informed by state-of-the-art three-dimensional numerical

models

Hiroki Nagakura1⋆, Adam Burrows1, David Vartanyan2, David Radice3,41Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA2Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720, USA3Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA4Department of Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA

Accepted XXX. Received YYY; in original form ZZZ

ABSTRACT

Based on our recent three-dimensional core-collapse supernova (CCSN) simulationsincluding both exploding and non-exploding models, we study the detailed neutrinosignals in representative terrestrial neutrino observatories, Super-Kamiokande (Hyper-Kamiokande), DUNE, JUNO, and IceCube. We find that the physical origin of differ-ence in the neutrino signals between 1D and 3D is mainly proto-neutron-star (PNS)convection. We study the temporal and angular variations of the neutrino signals anddiscuss the detectability of the time variations driven by the spiral Standing Accre-tion Shock Instability (spiral SASI) when it emerges for non-exploding models. Inaddition, we determine that there can be a large angular asymmetry in the eventrate (& 50%), but that the time-integrated signal has a relatively modest asymmetry(. 20%). Both features are associated with the lepton-number emission self-sustainedasymmetry (LESA) and the spiral SASI. Moreover, our analysis suggests that there isan interesting correlation between the total neutrino energy (TONE) and the cumula-tive number of neutrino events in each detector, a correlation that can facilitate dataanalyses of real observations. We demonstrate the retrieval of neutrino energy spectrafor all flavors of neutrino by applying a novel spectrum reconstruction technique to thedata from multiple detectors. We find that this new method is capable of estimatingthe TONE within the error of ∼20% if the distance to the CCSN is . 6 kpc.

Key words: neutrinos - supernovae: general.

1 INTRODUCTION

A core-collapse supernova (CCSN) arises from a catas-trophic death of a massive star (M & 8M⊙). During thedevelopment of the explosion and the cooling of the proto-neutron star (PNS), a total energy of ∼3 ×1053erg is radi-ated. Indeed, a neutrino burst associated with a CCSN wasdirectly detected from SN 1987A by the terrestrial neutrinodetectors Kamiokande (Hirata et al. 1987) and the IMB(Irvine–Michigan–Brookhaven) (Bionta et al. 1987). Theydetected a total of 19 events with neutrino energies rang-ing from ∼ 5 MeV to ∼ 40 MeV and the event lasted ∼ 10seconds; this is consistent with our understanding of the dy-namics of CCSN, albeit very crudely. On the other hand, dueto low number of events and poor flavor sensitivity, these ob-servations did not provide enough information to constrain

⋆ E-mail: hirokin@astro.princeton.edu

the explosion mechanism . This is a major opportunity forthe future.

A large number of neutrino detectors with sensi-tivities to multiple neutrino flavors should be availablewhen the next galactic CCSN happens. Super-Kamiokande(SK), one of the currently operating water-Cherenkov neu-trino detectors, is capable of detecting ∼ 10, 000 neutri-nos from a CCSN at the distance of 10 kpc (Abe et al.2016); Hyper-Kamiokande (HK) is essentially a scaled-up version of SK by a factor of several in volume(Hyper-Kamiokande Proto-Collaboration et al. 2018) andthe project has recently been officially approved. The deepunderground neutrino experiment (DUNE) is a liquid-Argondetector which will have a unique sensitivity to electron-typeneutrinos (νe) (Acciarri et al. 2016; Ankowski et al. 2016).The Jiangmen Underground Neutrino Observatory (JUNO),one of the upcoming liquid-scintillator detectors, is designedmainly to determine the neutrino mass hierarchy by a precise

c© 2020 The Authors

Prepared for submission to JHEP KCL-2020-27, FTUV-20-0625.4735, IFIC/20-33

Relaxing Cosmological Neutrino Mass Bounds with

Unstable Neutrinos

Miguel Escudero,1a Jacobo Lopez-Pavon,2b Nuria Rius,3b and Stefan Sandner,4b

aTheoretical Particle Physics and Cosmology Group, Department of Physics,

King’s College London, Strand, London WC2R 2LS, UKbDepartamento de Fısica Teorica and IFIC, Universidad de Valencia-CSIC

C/ Catedratico Jose Beltran, 2, E-46980 Paterna, Spain

E-mail: miguel.escudero@kcl.ac.uk, jlpavon@ific.uv.es, nuria.rius@ific.uv.es,

stefan.sandner@ific.uv.es

Abstract: At present, cosmological observations set the most stringent bound on the neutrino mass

scale. Within the standard cosmological model (ΛCDM), the Planck collaboration reports∑mν <

0.12 eV at 95 % CL. This bound, taken at face value, excludes many neutrino mass models. However,

unstable neutrinos, with lifetimes shorter than the age of the universe τν . tU , represent a particle

physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino

decay modes, categorizing them in terms of particle content and final decay products. Taking into

account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into

BSM particles are a promising option to relax cosmological neutrino mass bounds. We then build a

simple extension of the type I seesaw scenario by adding one sterile state ν4 and a Goldstone boson φ,

in which νi → ν4 φ decays can loosen the neutrino mass bounds up to∑mν ∼ 1 eV, without spoiling

the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the

right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement

this idea in the context of minimal neutrino mass models based on a U(1)µ−τ flavor symmetry, which

are otherwise in tension with the current bound on∑mν .

1ORCID: 0000-0002-4487-87422ORCID: 0000-0002-9554-50753ORCID: 0000-0002-0606-42974ORCID: 0000-0002-1802-9018

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An Attractive Scenario for Light Dark Matter Direct Detection

Hooman Davoudiasl,∗ Peter B. Denton,† and Julia Gehrlein‡

High Energy Theory Group, Physics Department,Brookhaven National Laboratory, Upton, NY 11973, USA

(Dated: July 13, 2020)

Direct detection of light dark matter (DM), below the GeV scale, through electron recoil canbe efficient if DM has a velocity well above the virial value of v ∼ 10−3. We point out that ifthere is a long range attractive force sourced by bulk ordinary matter, i.e. baryons or electrons,DM can be accelerated towards the Earth and reach velocities v ∼ 0.1 near the Earth surface. Inthis “attractive scenario,” all DM will be boosted to high velocities by the time it reaches directdetection apparatuses in laboratories. We elucidate the implications of this scenario for electronrecoil direct detection experiments and find parameters that could lead to potential signals, whilebeing consistent with stellar cooling and other bounds. Our scenario can potentially explain therecent excess in electron recoil signals reported by the XENON1T experiment in the ∼ keV energyregime.

INTRODUCTION

A variety of astronomical and cosmological observa-tions have established that the Universe contains a sub-stance of little, if any, interaction with ordinary mat-ter made of atoms. This substance, dark matter (DM),comprises about 25% of the cosmic energy budget, whichtranslates to about 85% of all matter in the Universe [1].Not much is known about non-gravitational propertiesof DM, due to its elusive nature. Given the diversity ofparticles and forces that constitute the “visible” sectorencoded in the Standard Model (SM) of particle physics,it is reasonable to consider whether DM resides within a“dark sector” that comprises a number of new states andforces that only feebly interact with the SM.

There has been a significant experimental effort overthe last few decades to detect DM in the laboratory. Thiseffort has been matched by intense theoretical researchdirected at DM phenomenology. The questions surround-ing the physics underlying electroweak symmetry break-ing in the SM and its extensions led to an early focus tolook for DM around the weak scale ∼ 100 GeV. The lackof evidence for new physics near that scale, from high en-ergy and precision experiments, together with null signalsfor weak scale DM in a variety of searches, has providedmotivation to expand the experimental and theoreticalefforts to lower masses, where new challenges arise. Inthe realm of direct detection, going to lower DM massesmeans smaller available energies in collisions of DM par-ticles with detector target material, which requires lowerdetection energy thresholds and controlling backgroundsthat could overwhelm the signal.

Searches designed for weak scale DM are mostly fo-cused on looking for nuclear recoil signals. However, di-rect detection of light DM, below the GeV scale, moti-vates looking for electron recoil signals. To see this, letus consider some rough estimates. The typical virial ve-locity of DM near the solar system is v ∼ 10−3. Forheavy DM masses, mDM ∼ 100 GeV, this corresponds

to a nucleus of mass mN ∼ 10 GeV recoiling with mo-mentum of order q ∼ mN v ∼ 10−2 GeV and energyER ∼ q2/(2mN ) ∼ 10 keV. Now, if we consider sub-GeV DM masses, say mDM ∼ 0.1 GeV, we see that themomentum transfer is q ∼ mDM v ∼ 100 keV and thenucleus would recoil with energy ER ∼ eV, which is wellbelow the & keV threshold of such experiments.

The above situation can be improved if one looks forelectron recoil signals. To see this, note that electrons inatoms are delocalized over length scales of order Bohrradius a0 ∼ (αme)

−1, where α ≈ 1/137 is the finestructure constant and me ≈ 511 keV is the electronmass. Thus, the typical momentum of the electrons inthe atom is q0 ∼ 1/a0 and the electron velocity is henceve ∼ α, which is much larger than the virial velocity ofDM. Nonetheless, the recoil energy of the electron willbe ER ∼ q20/(2me) ∼ 10 eV. Hence, detection of a sig-nal in electron recoil in an experiment with & keV en-ergy threshold requires velocities near v ∼ 0.1, whichis well above the escape velocity from the Milky Way,vesc ∼ few × 10−3, severely suppressing the expectedabundance of any such DM particles in the halo pop-ulation.

Given the above situation, to look for typical DM inthe sub-GeV regime, one needs to devise experimentaltechniques with detection thresholds keV [2–6] (fornovel ideas see [7–10]). Alternatively, one could investi-gate new DM models that could be detected in the cur-rent class of large scale experiments like XENON1T orthe planned next generation searches such as XENONnTand LZ [11–13], with thresholds near the keV scale. Infact, there have been some ideas put forth in recent yearswhere a fraction of the DM can have velocities 10−3,due to originating from decays of a more massive DMstate [14–16] or else due to interactions with energeticparticle, such as cosmic rays [17]. In these schemes, typ-ically only a small fraction of DM could be boosted tohigher velocities.

In what follows, we will propose a novel scenario, where

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EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)

Submitted to: Phys. Rev. D CERN-EP-2020-073July 13, 2020

Search for resonances decaying into a weak vectorboson and a Higgs boson in the fully hadronic final

state produced in proton–proton collisions at√s = 13 TeV with the ATLAS detector

The ATLAS Collaboration

A search for heavy resonances decaying into a W or Z boson and a Higgs boson producedin proton–proton collisions at the Large Hadron Collider at

√s = 13 TeV is presented. The

analysis utilizes the dominant W → qq′ or Z → qq and H → bb decays with substructuretechniques applied to large-radius jets. A sample corresponding to an integrated luminosityof 139 fb−1 collected with the ATLAS detector is analyzed and no significant excess of datais observed over the background prediction. The results are interpreted in the context of theHeavy Vector Triplet model with spin-1 W ′ and Z ′ bosons. Upper limits on the cross sectionare set for resonances with mass between 1.5 and 5.0 TeV, ranging from 6.8 to 0.53 fb forW ′→ WH and from 8.7 to 0.53 fb for Z ′→ ZH at the 95% confidence level.

© 2020 CERN for the benefit of the ATLAS Collaboration.Reproduction of this article or parts of it is allowed as specified in the CC-BY-4.0 license.

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1 Introduction

The search for physics beyond the Standard Model (SM) is a major focus of the physics program at theLarge Hadron Collider (LHC). Since its discovery [1, 2], the Higgs boson has become a tool in this search.In particular, one may expect new heavy resonances to couple to Higgs bosons and weak vector bosons(V = W or Z). Such resonances are expected to occur in a number of theories beyond the Standard Model.Theories that aim to solve the naturalness problem predict the existence of vector resonances as expected incomposite Higgs models [3, 4], Little Higgs models [5], or models with extra dimensions [6, 7]. Theorieswith extended Higgs sectors predict scalar resonances as in two-Higgs-doublet models [8].

In this article, a search forWH and ZH resonances produced in proton–proton (pp) collisions at√

s = 13TeVis reported with a sample corresponding to an integrated luminosity of 139 fb−1 collected with the ATLASdetector during Run 2 of the LHC in 2015–2018. The search is designed for resonances with a mass ofat least 1.5 TeV and with both the V and H bosons decaying hadronically in the modes V → qq(′) andH → bb, as shown in Figure 1. In this regime, the V and H bosons are produced with high transversemomentum (pT), resulting in each boson being reconstructed as a single large-radius hadronic jet, and theinvariant mass of this dijet system provides the final discriminating variable. Jet substructure techniquesand b-tagging are then used to discriminate those jets from background jets originating from multijet,V+jets, and tt events – with QCD multijet events representing at least 85% of the total background. Due todifficulties in modeling the background from simulation, all background estimates are derived from thedata.

Figure 1: Feynman diagram for the production of a V ′ resonance with decay into a VH pair.

The results of the search are interpreted in the context of the heavy vector triplet (HVT) model [9], which isa simplified model providing a broad phenomenological framework for heavy resonances coupling to SMfermions and bosons. In this model, W ′ and Z ′ vector bosons interact with quarks and the Higgs field withcoupling strength of gq and gH , respectively.1 Coupling to the Higgs field gives rise to interactions withlongitudinally polarized W and Z bosons. Two scenarios are considered as benchmarks for interpretationin this article. Model A corresponds to the choice gq = −0.55 and gH = −0.56, which reproducesthe phenomenology of weakly coupled models based on an extended gauge symmetry [11]. Model B

1 Further details about the use of the HVT model in ATLAS analyses can be found in Ref. [10].

2

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-EP-2020-1202020/07/13

CMS-HIG-19-012

Search for decays of the 125 GeV Higgs boson into a Zboson and a ρ or φ meson

The CMS Collaboration∗

Abstract

Decays of the 125 GeV Higgs boson into a Z boson and a ρ0(770) or φ(1020) mesonare searched for using proton-proton collision data collected by the CMS experimentat the LHC at

√s = 13 TeV. The analysed data set corresponds to an integrated lu-

minosity of 137 fb−1. Events are selected in which the Z boson decays into a pair ofelectrons or a pair of muons, and the ρ and φ mesons decay into pairs of pions andkaons, respectively. No significant excess above the background model is observed.As different polarization states are possible for the decay products of the Z bosonand ρ or φ mesons, affecting the signal acceptance, scenarios in which the decays arelongitudinally or transversely polarized are considered. Upper limits at the 95% con-fidence level on the Higgs boson branching fractions into Zρ and Zφ are determinedto be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the consideredpolarization scenarios; these values are 740–940 and 730–950 times larger than the re-spective standard model expectations. These results constitute the first experimentallimits on the two decay channels.

Submitted to the Journal of High Energy Physics

c© 2020 CERN for the benefit of the CMS Collaboration. CC-BY-4.0 license

∗See Appendix A for the list of collaboration members

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The hydrodynamic gradient expansion in linear response theory

Michal P. Heller,1, 2, ∗ Alexandre Serantes,2, † Micha l Spalinski,2, 3, ‡

Viktor Svensson,2, 1, § and Benjamin Withers4, ¶

1Max Planck Institute for Gravitational Physics (Albert Einstein Institute), 14476 Potsdam-Golm, Germany2National Centre for Nuclear Research, 02-093 Warsaw, Poland

3Physics Department, University of Bia lystok, 15-245 Bia lystok, Poland4Mathematical Sciences and STAG Research Centre,

University of Southampton, Highfield, Southampton SO17 1BJ, UK

One of the foundational questions in relativistic fluid mechanics concerns the properties of thehydrodynamic gradient expansion at large orders. Studies of expanding systems arising in heavy-ion collisions and cosmology show that the expansion in real space gradients is divergent. On theother hand, expansions of dispersion relations of hydrodynamic modes in powers of momenta have anon-vanishing radius of convergence. We resolve this apparent tension finding a beautifully simpleand universal result: the real space hydrodynamic gradient expansion diverges if initial data havesupport in momentum space exceeding a critical value, and converges otherwise. This critical valueis an intrinsic property of the microscopic theory, and corresponds to a branch point of the spectrumwhere hydrodynamic and nonhydrodynamic modes first collide.

Introduction– The goal of relativistic hydrodynamicsis to provide an effective description of long-lived, longwavelength degrees of freedom – hydrodynamic modes –which are generally expected to dominate nonequilibriumdynamics of collective states of quantum field theories atmacroscopic scales and sufficiently late times [1]. Un-derstanding what exact scales and times these are hasbeen a very active field of research of the past decade inconnection with studies of collective phases of strong in-teractions in relativistic heavy-ion collisions at RHIC andLHC [2, 3]. In these settings, relativistic hydrodynam-ics is the framework translating between the spectrumof low-energy particles observed in detectors and micro-scopic features such as information about initial state,equation of state and interaction strength [4, 5]. Re-lated recent developments in relativistic hydrodynamicsgo well beyond the realm of nuclear physics and extendalso to astrophysics [6–8], as well as to studies of stronggravity [9, 10].

Much progress on the emergence of relativistic hydro-dynamics has occurred recently thanks to, one one hand,viewing hydrodynamics as an effective field theory for-mulated in a spacetime derivative expansion [11] and, onthe other, using insights from linear response theory [12].

The effective field theory approach expresses expecta-tion values of conserved currents in terms of derivativesof local classical fields. For the energy-momentum ten-sor 〈Tµν〉 these can be chosen as the energy density Eand a normalized fluid velocity Uµ. The energy momen-tum tensor is represented as a sum of all possible termsgraded by the number of derivatives, starting with theperfect fluid contribution. The foundational importanceof this expansion is that at a formal level it is unique andwell defined in any system which is known to equilibrate.By comparing this formal series to the analogous gradi-ent expansion calculated in a microscopic theory one canexpress the parameters appearing in the hydrodynamic

series – transport coefficients – in terms of microscopicquantities. Interestingly, the gradient series evaluated ona solution of the evolution equations can have a vanish-ing radius of convergence at least in the case of highly-symmetric flows describing rapidly expanding matter, aswas discovered in AdS/CFT calculations [13–15], hydro-dynamic models [16–18] and kinetic theory [19, 20].

In linear response theory [21], the response of the sys-tem is governed by sums of harmonic contributions withcomplex frequencies which encode Fourier space singu-larities of retarded correlators [22]. Imaginary parts ofthese frequencies capture effects of dissipation. Terms as-sociated with frequencies which vanish at small momen-tum correspond to shear and sound mode hydrodynamicexcitations, while the rest represents transient phenom-ena [2]. The gradient expansion of the hydrodynamicconstitutive relations translates here into series in spa-tial momentum for shear and sound mode frequencies. InRef. [23] and later in Refs. [24, 25] it was observed thatsuch a series has a finite non-zero radius of convergence,which is governed by the presence of nonhydrodynamicmodes. This parallels the fact that the Borel transform ofthe gradient expansion in an expanding plasma similarlyreveals information about the nonhydrodynamic sectors.These transient excitations are present in all relativisticmodels which do not violate causality.

The present Letter combines these two lines of re-search [26] in a novel way, which allows us to make forthe first time rather generic statements about the con-vergence of the hydrodynamic gradient expansion acrossmicroscopic theories and models. In particular, we showthat the convergence of the real space gradient expan-sion of the constitutive relations in the linearized regimeis governed by the same mechanism that yields a finite ra-dius of convergence of series expansions of hydrodynamicmode frequencies at small momentum.

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Prepared for submission to JCAP

Global fits of axion-like particles toXENON1T and astrophysical dataPeter Athron,a Csaba Balazs,a Ankit Beniwal,b J. ElielCamargo-Molina,c Andrew Fowlie,d Tomas E. Gonzalo,a SebastianHoof,e Felix Kahlhoefer,f David J. E. Marsh,e Markus TobiasPrim,g Pat Scott,h,c Wei Su,i Martin White,i Lei Wud and YangZhangaaSchool of Physics and Astronomy, Monash University, Melbourne, Victoria 3800, AustraliabCentre for Cosmology, Particle Physics and Phenomenology (CP3), Universite catholiquede Louvain, B-1348 Louvain-la-Neuve, BelgiumcDepartment of Physics, Imperial College London, Blackett Laboratory, Prince ConsortRoad, London SW7 2AZ, UKdDepartment of Physics and Institute of Theoretical Physics, Nanjing Normal University,Nanjing, Jiangsu 210023, ChinaeInstitut fur Astrophysik, Georg-August Universitat, Gottingen, Friedrich-Hund-Platz 1,37077 Gottingen, Germanyf Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University,D-52056 Aachen, GermanygPhysikalisches Institut der Rheinischen Friedrich-Wilhelms-Universitat Bonn, 53115 Bonn,GermanyhSchool of Mathematics and Physics, The University of Queensland, St. Lucia, Brisbane,QLD 4072, AustraliaiARC Centre of Excellence for Dark Matter Particle Physics & CSSM, Department ofPhysics, University of Adelaide, Adelaide, SA 5034

E-mail: hoof@uni-goettingen.de, andrew.j.fowlie@njnu.edu.cn

Abstract. The excess of electron recoil events seen by the XENON1T experiment has beeninterpreted as a potential signal of axion-like particles (ALPs), either produced in the Sun,or constituting part of the dark matter halo of the Milky Way. It has also been explainedas a consequence of trace amounts of tritium in the experiment. We consider the evidencefor the solar and dark-matter ALP hypotheses from the combination of XENON1T dataand multiple astrophysical probes, including horizontal branch stars, red giants, and whitedwarfs. We briefly address the influence of ALP decays and supernova cooling. While thedifferent datasets are in clear tension for the case of solar ALPs, all measurements can besimultaneously accommodated for the case of a sub-dominant fraction of dark-matter ALPs.Nevertheless, this solution requires the tuning of several a priori unknown parameters, suchthat for our choices of priors a Bayesian analysis shows no strong preference for the ALPinterpretation of the XENON1T excess over the background hypothesis.

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Gravitational-wave detectors as particle-physics laboratories:Constraining scalar interactions with boson-star binaries

Costantino Pacilio,∗ Massimo Vaglio,† Andrea Maselli,‡ and Paolo Pani§

Dipartimento di Fisica, “Sapienza” Universita di Roma & Sezione INFN Roma1, Roma 00185, Italy

Gravitational-wave (GW) detections of binary neutron star coalescences play a crucial role toconstrain the microscopic interaction of matter at ultrahigh density. Similarly, if boson stars existin the universe their coalescence can be used to constrain the fundamental coupling constants ofa scalar field theory. We develop the first coherent waveform model for the inspiral of boson starswith quartic interactions. The waveform includes coherently spin-induced quadrupolar and tidal-deformability contributions in terms of the masses and spins of the binary and of a single couplingconstant of the theory. We show that future instruments such as the Einstein Telescope and LISAcan provide strong, complementary bounds on bosonic self-interactions, while the constraining powerof current detectors is marginal.

I. INTRODUCTION

Gravitational-wave (GW) measurements of the tidaldeformability of neutron stars (NSs) have opened a newwindow to study the properties of matter beyond thenuclear saturation point within stellar cores [1, 2]. Equa-tions of state with different stiffness provide tidal de-formabilities which may vary up to an order of magni-tude. This effect magnifies the details of the underlyingmicroscopic model, allowing to probe how fundamentalinteractions behave in extreme regimes [3, 4].

In this paper, we argue that the very same situationcan occur if boson stars (BSs) [5, 6] exist in the Uni-verse and form coalescing binaries within the horizon ofcurrent and future detectors. BSs are self-gravitatingcondensates of a bosonic field (see Refs. [7, 8] for somereviews). In their original and simplest proposal, theyare solutions to Einstein gravity minimally coupled to aclassical field theory for a complex scalar φ:

Lscalar =1

2∂µφ

?∂µφ+ V (|φ|) , (1)

where a star denotes complex conjugation and V is thescalar self potential. The latter plays the same role as theequation of state for NSs: different microscopic interac-tions give rise to macroscopically different properties ofthe boson stars.

Depending on the mass of the boson field and on theself-interaction terms, BSs can exist in any mass rangeand can have a compactness comparable to or larger thanthat of a NS. It is intriguing that current GW measure-ments cannot exclude the existence of exotic compactobjects other than black holes (BHs) and NSs, especiallyfor GW events in the low-mass [9] and high-mass gap,where neither BHs nor NSs are predicted in the standardscenario.

∗ costantino.pacilio@uniroma1.it† massimo.vaglio@uniroma1.it‡ andrea.maselli@roma1.infn.it§ paolo.pani@uniroma1.it

As a case study, in this paper we consider a simple classof quartic interactions [see Eq. (3)] and quantify the ac-curacy within which a GW detection of a BS coalescencecan constrain the fundamental parameters (boson massand coupling constants) of a given scalar field theory.

We focus on the inspiral phase, which can be accuratelymodeled with post-Newtonian (PN) theory [10, 11]. Upto 1.5 PN order (see below), the GW signal depends onlyon the masses and spins of the binary components and istherefore oblivious to the nature of the latter. However,the details of the coalescing bodies appears at higher PNorder, notably through the effects of the spin-inducedquadrupole moment (if the binary is spinning) [11, 12],a small tidal-heating term (if at least one of the bi-nary components is a BH or can efficiently absorb ra-diation) [13–15], and most importantly through the tidaldeformability contribution (the so-called tidal Love num-bers [11, 16, 17]) that becomes increasingly more relevantduring the late stages of the inspiral and merger, as inthe case of a binary NS coalescence (see, e.g., Refs. [2, 18]for some recent reviews).

Previous work considered the aforementioned effectsindependently and included in the waveform only a sin-gle effect at the time, focusing on the detectability ofthe tidal Love number [19, 20], or of the spin-inducedquadrupole moment [21–24], or of the tidal heatingalone [15, 25, 26]. However, this approach neglects acrucial ingredient: for a given scalar field theory (i.e., fix-ing the potential in the Lagrangian (1)), both the tidalLove numbers and the spin quadrupole moment dependonly on the masses and spins of the binary. Therefore,their concurrent inclusion does not increase the numberof waveform parameters and alleviates their degeneracy.

As we shall show, the sensitivity of current detectorssuch as LIGO and Virgo is not sufficient to place strin-gent constraints on the coupling constants of the the-ory. However, future facilities will provide much morestringent measurements. In particular we consider thefuture Laser Interferometer Space Antenna (LISA) [27],which can potentially detect supermassive binary BSs,and the Einstein Telescope (ET) [28], a proposed third-generation [29] ground-based GW detector. Putative de-

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USTC-ICTS/PCFT-20-20

Improved quark coalescence model for spin alignment and polarization of hadrons

Xin-Li Sheng,1 Qun Wang,1 and Xin-Nian Wang2, 3

1Peng Huanwu Center for Fundamental Theory and Department of Modern Physics,University of Science and Technology of China, Hefei, Anhui 230026, China

2Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics,Central China Normal University, Wuhan, Hubei 430079, China

3Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, California 94720

We propose an improved quark coalescence model for spin alignment of vector mesons and polar-ization of baryons by spin density matrix with phase space dependence. The spin density matrixis defined through Wigner functions. Within the model we propose an understanding of spin align-ments of vector mesons φ and K∗0 (including K∗0) in the static limit: a large positive deviation ofρ00 for φ mesons from 1/3 may come from the electric part of the vector φ field, while a negativedeviation of ρ00 for K∗0 may come from the electric part of vorticity tensor fields. Such a negativecontribution to ρ00 for K∗0 mesons, in comparison with the same contribution to ρ00 for φ mesonswhich is less important, is amplified by a factor of the mass ratio of strange to light quark timesthe ratio of

⟨p2b

⟩on the wave function of K∗0 to φ (pb is the relative momentum of two constituent

quarks of K∗0 and φ). These results should be tested by a detailed and comprehensive simulationof vorticity tensor fields and vector meson fields in heavy ion collisions.

I. INTRODUCTION

The Barnett effect [1] and the Einstein-de Haas effect [2] are two well-known effects in materials to connect rotationand spin polarization which can be converted from one to another. Similar effects also exist in ultra-relativistic heavy-ion collisions (HIC), in which a huge orbital angular momentum (OAM) can be generated in the direction perpendicularto the reaction plane and is transferred to the hot and dense medium in the form of the global polarization of hadrons[3–8] (see, e.g. [9–12], for recent reviews). In microscopic scenarios the transfer of OAM to spin polarization of hadronsis through the spin-orbit coupling in particle scatterings [3, 8, 13, 14], while in macroscopic approaches it is throughthe spin-vorticity coupling in the fluid [15–20]. The global polarization can be measured through the the polarizationof hyperons such as Λ (including Λ hereafter) since they have weak decay channels [3]. The STAR collaboration hasrecently measured a non-vanishing global polarization of Λ hyperons in Au+Au collisions at

√sNN = 7.7− 200 GeV

[21, 22].In principle vector mesons can also be polarized in heavy ion collisions, but the polarization of vector mesons cannot

be measured since they mainly decay through strong interaction. Instead, ρ00, the 00-element of the vector meson’sspin density matrix, can be meaured through the angular distribution of its decay daughters [4, 23]. If ρ00 6= 1/3, thedistribution is anisotropic and the spin of the vector meson is aligned to the spin quantization direction. In 2008, theSTAR collaboration measured ρ00 for the vector meson φ(1020) in Au+Au collisions at 200 GeV, but the result isconsistent to 1/3, indicating no spin alignment within errors [24]. Recent preliminary data of STAR for the φ meson’sρ00 (denoted as ρφ00 hereafter) at lower energies show a significant positive deviation from 1/3, which is beyondconventional understanding of the polarization [25]. In Ref. [26], some of us proposed that such a large positivedeviation of ρφ00 from 1/3 may possibly be explained by the φ field. In such a proposal [26], a quark coalescencemodel is employed which is based on spin density operators in momentum space [23]. As the quark polarizationcomes mainly from vorticity and vector meson fields which are functions of space-time, the space dependence of thequark polarization in Ref. [26] is put in a phenomenological way. The purpose of this paper is to improve the quarkcoalescence model of Ref. [23] by defining and using spin density operators in phase space with the help of spinWigner functions. In such an improved quark coalescence model, the quark polarization as a function of space-timecan be treated in a rigorous and systematic way. So one can then naturally describe spin alignments of vector mesonssuch as φ and K∗0 (including K

∗0if not stated explicitly) as functions of space-time. It is expected to implement the

improved coalescence model in real time simulations and to provide insights in spin alignments of vector mesons.The paper is organized as follows. In Sect. II, we formulate the improved coalescence model through the spin

density matrix in phase space with coordinate dependence. In Sect. III, we give spin polarization of quarks in phasespace from vorticity and vector meson fields. In Sect. IV, we analyze global and local polarization of Λ (includingΛ if not stated explicitly) using the improved coalescence model. In Sect. V, using the improved coalescence modelwe formulate spin alignments of vector mesons φ and K∗0. In Sect. VI, we solve the Klein-Gordon equation to givevector meson fields generated by point charge sources. Finally we make a summary of the results.

Notations and conventions. We adopt the sign convention for the metric tensor gµν = (1,−1,−1,−1). A four-vector is represented by Greek indices, e.g, xµ or pµ with µ = 0, 1, 2, 3. A three-vector is represented in a boldfaced

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A New Window into Black Holes

Iosif Bena1 and Daniel R. Mayerson1

1Institut de Physique Theorique, Universite Paris-Saclay, CNRS,CEA, Orme des Merisiers 91191, Gif-sur-Yvette CEDEX, France

iosif.bena@ipht.fr, daniel.mayerson@ipht.fr

We develop a formalism to compute the gravitational multipole moments and ratios of momentsof non-extremal and of supersymmetric black holes in four dimensions, as well as of horizonlessmicrostate geometries of the latter. For supersymmetric and for Kerr black holes many of thesemultipole moments vanish, and their dimensionless ratios are ill-defined. We present two methodsto compute these dimensionless ratios, which for certain supersymmetric black holes agree spectac-ularly. We also compute these dimensionless ratios for the Kerr solution. Our methods allow us tocalculate an infinite number of hitherto unknown parameters of Kerr black holes, giving us a newwindow into their physics.

1. INTRODUCTION

There is an extended literature that argues that inorder for black hole evaporation to be consistent withquantum unitarity, there should exist a structure at thescale of the horizon of the black hole [1, 2]. This struc-ture, commonly referred as a fuzzball or firewall, hashighly unusual properties in that its stiffness preventsits immediate collapse into the black hole. The only top-down construction of such structure is given by blackhole microstate geometries [3–9], which are smooth hori-zonless solutions of String Theory that have the samemass and charge as a black hole but in which the horizonis replaced by a complicated structure of topologically-nontrivial bubbles wrapped by fluxes.

Understanding how the physics of this structure dif-fers from the physics of the black hole is of crucial im-portance, especially in the light of the recent observa-tions of gravitational waves emitted when two black holesmerge [10], and of future experiments that plan to ex-plore Extreme Mass-Ratio Inspiral (EMRI) gravity waves[11] that should reveal very detailed information abouthorizon-scale physics. One important way in which mi-crostate geometries differ from the black hole is in thehigher multipole moments of the mass and angular mo-mentum. Since EMRI gravitational waves are sensitiveto many of these multipole moments and invariant ra-tios thereof, it is a crucial problem to calculate preciselythese multipole moments for microstate geometries andto compare them to those of the corresponding black hole.

Most of the black hole microstate geometries that havebeen constructed so far correspond to extremal blackholes and so do not allow us to make quantitative pre-dictions that could be compared to what will measuredfrom EMRI gravitational waves. However, one can useextremal black holes and their microstates to understandqualitatively the new black-hole physics that can beglimpsed from the gravitational multipoles of microstategeometries, much as one uses the N = 4 SYM quark-gluon plasma to understand qualitatively features of thequark-gluon plasma in the real world.

In this Letter, we compute the gravitational multipoles

of generic non-extremal black holes in four dimensions,and of horizonless microstate geometries that have thesame mass and charges as the supersymmetric extremalblack hole. Because of its symmetry and lack of angularmomentum, all the gravitational multipoles of the super-symmetric (BPS) black hole vanish, with the exceptionof the mass, M0. However, for generic microstate geome-tries of this black hole all multipoles are finite. Further-more, in the “scaling limit” in which the throat of themicrostate geometries becomes very long, and they be-come more and more similar to the black hole, all theirextra multipoles vanish and only M0 survives.

However, one can also consider ratios of multipolemoments that stay finite in the scaling limit, such asthe product of the angular momentum and the currentquadrupole moment divided by the product of the massand the mass octopole moment:

S1S2

M3M0. (1)

This, and many other multipole ratios, cannot be com-puted in the four-dimensional BPS black hole solution,where they are zero over zero. Hence, by computing theseratios in the scaling limit of various microstate geome-tries, we obtain a whole set of new quantities that char-acterize the BPS black hole. We will call this method ofcomputing multipole ratios the direct BPS method.

There is another way in which one can try to com-pute multipole ratios that are undefined in the black-holegeometry. One can deform the supersymmetric blackhole into a nonextremal, rotating black hole, compute itsmultipole ratios and take back the supersymmetric, non-rotating limit. Similarly, we can use this indirect methodto compute multipole ratios that are undefined for theKerr black hole: one can deform it into a general chargedSTU black hole, compute multipole ratios, and take backthe charges to zero. In this way, we can associate well-defined multipole ratios with the Kerr black hole. Thesepreviously unknown ratios provide new constraints forany model that parameterizes departures from the Kerrsolution that may have an effect of gravitational waves.

For certain families of BPS black holes, the multipoleratios computed using these two methods are amazingly

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FERMILAB-PUB-20-280-AE-T

An Active-to-Sterile Neutrino Transition Dipole Moment and the XENON1T Excess

Ian M. Shoemaker,1, ∗ Yu-Dai Tsai,2, 3, 4, † and Jason Wyenberg5, ‡

1Center for Neutrino Physics, Department of Physics,Virginia Tech University, Blacksburg, VA 24601, USA

2Theory Department, Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA3Cosmic Physics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510, USA4Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA

5Department of Physics, University of South Dakota, Vermillion, SD 57069, USA(Dated: July 13, 2020)

In this short letter, we find that a magnetic transition dipole moment between tau and sterileneutrinos can account for the XENON1T excess events. Unlike the ordinary neutrino dipole moment,the introduction of the new sterile mass scale allows for astrophysical bounds to be suppressed.Interestingly, the best-fit regions that are compatible with the SN1987A imply either boron-8 orCNO neutrinos as the source flux. We find that sterile neutrinos of either ∼ 260 keV or in the∼(500 – 800) keV mass range are capable of evading astrophysical constraints while being able tosuccessfully explain the XENON1T event rate. The sterile neutrino in the best fit parameter spacemay have significant effects on big bang nucleosynthesis (BBN). We show the region in which a lowreheating temperature of the Universe may allow the BBN constraints to be alleviated.

I. INTRODUCTION

The nature of particle physics beyond the StandardModel (SM) remains unknown. However, we have twokey hints about the nature of new physics: it must ac-count for the non-luminous dark matter (DM), and itmust account for neutrino masses. Interestingly, DMdirect-detection experiments are sufficiently sensitive tobe leading players in searching for novel neutrino inter-actions that may potentially help solve the mystery ofneutrino masses.

This context makes the recent excess of electron recoilevents at XENON1T [1] all the more intriguing. Neu-trino magnetic moments were originally studied by theXENON1T collaboration as potential explanations to theexcess (axions, dark photons, and other DM proposalswere also discussed in [2–55]). However, the couplingsfound tend to exceed the bounds from various astrophysi-cal systems. In this paper, we highlight a neutrino dipole-portal interaction that can account for the signal, whileevading astrophysical bounds (though still could be sub-ject to cosmological bounds). This results from the intro-duction of a new mass scale to the neutrino interaction.

The most commonly studied models accounting forneutrino masses introduce right-handed sterile neutrinos,N , via the interaction L ⊃ HNL. However, it is impor-tant to stress that such singlet states need not domi-nantly interact with the SM through this particular op-erator. Viable scenarios exist in which the dominant in-teraction comes from an active-to-sterile dipole moment,sometimes referred to as the “neutrino dipole portal,”

L ⊃ d (νLσµνFµνN) + h.c., (1)

∗ shoemaker@vt.edu† ytsai@fnal.gov‡ jason.wyenberg@coyotes.usd.edu

where Fµν is the electromagnetic field strength, σρσ =i2 [γρ, γσ], νL is the SM neutrino, and the coefficient d withunits of (mass)−1 controls the strength of the interac-tion. This transition dipole moment has been studied inthe context of MiniBooNE [56–63], and future projectedbounds have been studied for IceCube [64], SHiP [62],and direct-detection experiments [65].

Note that this operator can be induced through loopprocesses with the ordinary HNL operator, and in mostcases, mixing between N and SM neutrinos would alsobe induced. We focus our attention on the operator in

XENON1T Events

Background

Signal

Signal+Background

5 10 15 20 25 300

50

100

150

Er [keV]

Events/(t·y·keV

)

FIG. 1. Dipole portal best fit signal spectrum at XENON1Twithm4 = 640 keV and d = 2.2×10−9 µB . The background isshown in dashed black, the signal is solid red, and the signalplus background is shown in solid blue. Included in theseevent rates are the energy-dependent signal efficiency.

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The determination of the spin and parity of a vector-vector system

Mikhail Mikhasenko,1, ∗ Liupan An,2 and Ronan McNulty3

1CERN-EP, CH-1211, Geneva, Switzerland2INFN Sezione di Firenze, Firenze, Italy

3School of Physics, University College Dublin, Dublin 4, Ireland(Dated: July 13, 2020)

We present a construction of the reaction amplitude for the inclusive production of a resonancedecaying to a pair of identical vector particles such as J/ψJ/ψ, ρρ, φφ, or ZZ. The method providesthe possibility of determining the spin and parity of a resonance in a model-independent way. Atest of the methodology is demonstrated using the Standard Model decay of the Higgs boson to fourleptons.

I. INTRODUCTION

The formation of hadronic matter is one of the few poorly understood parts of Quantum Chromodynamics (QCD).QCD is the fundamental theory of the strong interaction, but the quarks and gluons that constitute its degrees offreedom can only be resolved in hard processes with large momentum transfer. At lower energy scales where hadronsemerge, perturbative QCD is not applicable. The quark model (QM) [1, 2] works well in classifying conventionalhadronic states into mesons and baryons built from the constituent quarks bound in the confined potential. Hadronsbeyond conventional mesons and baryons, such as glueballs containing constituent gluons, hybrid states containingquarks and gluons, and multiquark states, are referred to as exotic hadrons [3, 4]. They are allowed by the QM, howeverthey have not been seen experimentally until recently. Over the last decade overwhelming evidence has accumulated forexotic hadrons that include the observation of XY Z states in the charmonium spectrum [5], pentaquark states [6, 7],as well as resonance-like phenomena from the triangle singularity in hadron scattering [8]. Nevertheless, the overallpicture and the categorisation of these states remain unclear. The spin-parity of the observed exotic hadrons is acritical part of the formation puzzle. In most cases it can be accessed experimentally but the separation of the differentspin-parity hypotheses is often rather cumbersome and requires a case-by-case treatment. In this paper we addressthe problem of the spin-parity assignment for a system of two identical vectors that decay to a pair of leptons or apair of scalar particles.

Amongst the many applications of the presented framework, we note three in particular. First, it facilitates futurestudies of the resonance-like structure in the J/ψJ/ψ spectrum recently reported by LHCb [9]. The knowledge of itsquantum numbers will help to understand the mechanism for the binding of four charm quarks [10]. Second, it can beapplied in investigations of the central exclusive production (CEP) of vector-meson pairs. The colour-free gluon-richproduction mechanism of CEP makes the ρρ [11–13] and φφ [14, 15] channels particularly suited to searches forglueballs. The proposed approach sets the ground for a complete partial wave analysis of the high statistics CEP offour scalar mesons that should be possible with modern LHC data. Third, one finds the same vector-vector signaturein the Standard Model (SM) decay of the Higgs boson, H → ZZ. In studies of the spin-parity quantum numbers ofthe Higgs boson performed by both the ATLAS [16] and CMS [17] collaborations, to reach the conclusion that theobserved Higgs boson is consistent with the 0+ hypothesis, several phenomenological models were compared usingthe combined datasets from several decay channels. In contrast, here we discuss the anatomy of an assumption-freeapproach.

The two key constraints that determine the decay properties are parity conservation and permutation symmetry.One consequence of these constraints is the Landau-Yang theorem [18, 19], which states that a massive boson withJP = 1± cannot decay into two on-shell photons. The statement follows naturally from the general equations weprovide. Moreover, the extension of the selection rule to all natural quantum numbers with odd spin is easily obtained.A parity-signature test for a signal in the φφ system has been discussed in the past by several authors [20, 21]. Wederive results consistent with previous work using modern conventions on the state vectors and rotation matrices. Inaddition, we suggest exploring the spin-parity hypothesis using the full power of multidimensional test statistics.

The paper is organized as follows. The reaction amplitude is presented in Sec. II. In Sec. III the symmetry constraintsare discussed. We propose a test statistic discriminator in Sec. IV, and demonstrate the method on the SM H → ZZ

∗e-mail: mikhail.mikhasenko@cern.ch

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Prepared for submission to JHEP CERN-TH-2020-108, CP3-20-31

Tree-level splitting amplitudes for a gluon into

four collinear partons

Vittorio Del Duca1a Claude Duhrb Rayan Haindla Achilleas Lazopoulosa Martin Michelc

aInstitute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland.bTheoretical Physics Department, CERN, CH-1211 Geneva 23, Switzerland.cCenter for Cosmology, Particle Physics and Phenomenology (CP3),

UCLouvain, B-1348, Louvain-La-Neuve, Belgium.

E-mail: delducav@itp.phys.ethz.ch, claude.duhr@cern.ch,

haindlr@phys.ethz.ch, lazopoli@phys.ethz.ch,

martin.michel@uclouvain.be

Abstract: We compute in conventional dimensional regularisation the tree-level

splitting amplitudes for a gluon parent which splits into four collinear partons. This

is part of the universal infrared behaviour of the QCD scattering amplitudes at next-

to-next-to-next-to-leading order (N3LO) in the strong coupling constant. Combined

with our earlier results for a quark parent, this completes the set of tree-level splitting

amplitudes required at this order. We also study iterated collinear limits where a subset

of the four collinear partons become themselves collinear.

1On leave from INFN, Laboratori Nazionali di Frascati, Italy.

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Masses, Radii and Regge Trajectories of Σ−uState Hybrid

Charmonium

Nosheen Akbar∗

∗Department of Physics, COMSATS University Islamabad, Lahore Campus,

Lahore(54000), Pakistan.

Abstract

In this paper, masses and radii of Σ−

ustates hybrid charmonium mesons are calculated by

numerically solving the Schrodinger equation with non-relativistic potential model. Resultsfor calculated masses of Σ−

ustates charmonium hybrid mesons are found to be close to the

results obtained through lattice simulations. Calculated masses are used to construct Reggetrajectories. It is found that the trajectories are almost linear and parallel.

I. INTRODUCTION

Study of charmonium mesons is very important in particle physics. Conventional charmoniummesons, that can be described by the quark model, are the charm quark–antiquark pairs boundedwith ground state gluonic field; while hybrid charmonium mesons are the quark–antiquark pairswith excited state gluonic field. In [1, 2], quarkonium hybrid mesons are discussed throughlattice simulations and potentials for different states of quarkonium hybrids are plotted in fig.3of [2]. These states are characterized by quantum numbers, J, L, S, Λ, η, and ǫ, where J =L ⊕ S with L as the orbital angular momentum quantum number and S as the spin angularmomentum quantum number. Λ is the projection of the total angular momentum of gluonsand for Λ = 0,±1,±2,±3, ...., meson states are represented as Σ,Π,∆ and so on [1]. η is thecombination of parity and charge and for η = P C = +,−, states are labelled by sub-scriptg, u [1]. ǫ is the eigen value corresponding to the operator P and is equal to +,−. Parity andcharge for hybrid static potentials are defined as [1]

P = ǫ(−1)L+Λ+1, C = ǫη(−1)L+Λ+S , (1)

The low-lying static potential states are labelled as Σ+g ,Σ

−

g ,Σ+u ,Σ

−

u ,Πg,Πu,∆g,∆u and soon[1]. Σ+

g is the low-lying potential state with ground state gluonic field and is approximated

by a coulomb plus linear potential. The Πu and Σ−

u are the QQ potential states with lowlying gluonic excitations. Linear plus coulombic potential model is extended in [3] for Πu statesby fitting the suggested ansatz with lattice data[2] and the extended model is tested by findingproperties of mesons for a variety of JPC states in refs.[3, 4, 5, 6]. In ref.[7], linear plus coulombicpotential model is extended for lowest excited hybrid state, Σ−

u by fitting the lattice data [1]with the suggested analytical expression (ansatz). The validity of suggested ansatz is testedby calculating the spectrum of Σ−

u state bottomonium mesons. In this paper, this extendedpotential model[7] is used to calculate the spectrum and radii of the of Σ−

u charmonium hybridmesons. For this purpose, Born-Oppenheimer formalism and adiabatic approximation is used.

∗e mail: nosheenakbar@cuilahore.edu.pk,noshinakbar@yahoo.com

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Charge Distributions of Moving Nucleons

Cedric Lorce1

1CPHT, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Route de Saclay, 91128 Palaiseau, France

Relativistic charge distributions of targets with arbitrary average momentum are introduced.They provide an interpolation between the usual Breit frame and infinite-momentum frame distri-butions. We find that Breit frame distributions can be interpreted from a phase-space perspectiveas internal charge quasi-densities in the rest frame of a localized target, without any relativistic cor-rection. We show also that the apparent discrepancies between Breit frame and infinite-momentumframe distributions simply result from kinematical artifacts associated with spin.

PACS numbers: 14.20.Dh, 13.40.Gp

Electromagnetic form factors (FFs) of nucleons andnuclei have been measured over the last decades to animpressive level of precision, see e.g. [1–4]. They describehow the target reacts in an elastic scattering withoutgetting excited, and contain therefore information aboutthe internal distribution of charge and magnetization.

According to textbooks, FFs can be interpreted asFourier transforms of charge and magnetization distri-butions. Since relativistic wave functions are frame de-pendent, Fourier transforms are often restricted to theBreit frame (BF) [5, 6], where calculations formally yieldthe same results as in the non-relativistic domain. Con-cerns about the physical meaning of BF distributionshave however been expressed [7, 8], and their relationto genuine rest-frame distributions is usually thought toinvolve unclear and ambiguous relativistic corrections [9].

A strict density or probabilistic interpretation is tiedto Galilean symmetry. In quantum field theory, it canonly be justified when the momentum transfer remainssmall compared to the target inertia. Accordingly, theconcept of rest-frame density is intrinsically limited bythe Compton wavelength. One can however avoid theselimitations in the infinite-momentum frame (IMF), wherethe target inertia becomes formally infinite [10–13]. Theprice to pay is that the corresponding densities are nowtwo-dimensional and appear to be distorted due to themotion of the target relative to the observer [14, 15].

A phenomenological analysis of experimental data con-cluded that the center of the IMF charge distribution ofthe neutron is negative [16], in flagrant conflict with therest-frame picture suggested by both gluon-exchange andmeson-cloud models. Despite numerous efforts devotedto understanding this phenomenon, a fully convincingexplanation has so far never been obtained.

Relaxing the requirement of a strict density interpreta-tion, we show in the following that meaningful 2D chargedistributions free of relativistic corrections can be definedfor localized targets with arbitrary average momentum.They provide the natural interpolation between BF andIMF distributions and allow one to track down all distor-tions induced by the motion of the target. In particular,we find that a negative center in the neutron IMF dis-

tribution does not contradict the rest-frame picture andsimply results from relativistic kinematical effects asso-ciated with spin.We start with the observation that Lorentz symmetry

implies that relativistic charge distributions are generallyframe dependent. Their proper definition requires there-fore to adopt a phase-space perspective. In a quantumtheory, it has been known for a long time that the ex-pectation value of any operator O in a physical state |ψ〉can nicely be expressed as [17, 18]

〈O〉ψ =

∫d3P

(2π)3d3Rρψ(R,P )〈O〉R,P , (1)

where

ρψ(R,P ) ≡∫

d3z e−iP ·z ψ∗(R − z2 )ψ(R+ z

2 )

=

∫d3q

(2π)3e−iq·R ψ∗(P + q

2 )ψ(P − q

2 ).

(2)

defines the quantum phase-space or Wigner distribution.Because of Heisenberg’s uncertainty relations, Wignerdistributions receive only a quasi-probabilistic interpreta-tion: They give the quantum weight of finding the systemat average position R = 1

2 (x′ +x) with average momen-

tum P = 12 (p

′ + p). Strict probabilistic interpretation isrecovered under integration over position or momentum

∫d3Rρψ(R,P ) = |ψ(P )|2, (3)

∫d3P

(2π)3ρψ(R,P ) = |ψ(R)|2. (4)

Since wave-packet details have been factored out inEq. (1),

〈O〉R,P ≡∫

d3∆

(2π)3ei∆·R〈P + ∆

2 |O|P − ∆

2 〉 (5)

can be interpreted as the part associated with the inter-nal structure of the system. When Galilean symmetryapplies, 〈O〉R,P becomes P -independent and we recovera density interpretation owing to Eq. (4). Although thisformalism was originally developed in the non-relativistic

Anomalies in B Decays and Muon g − 2 from Dark Loops

Da Huanga,1, 2 Antonio P. Moraisb,1 and Rui Santosc3, 4

1Departamento de Fısica da Universidade de Aveiro and CIDMA,

Campus de Santiago, 3810-183 Aveiro, Portugal.

2National Astronomical Observatories,

Chinese Academy of Sciences, Beijing, 100012, China

3Centro de Fısica Teorica e Computacional, Faculdade de Ciencias,

Universidade de Lisboa, Campo Grande,

Edifıcio C8 1749-016 Lisboa, Portugal.

4ISEL - Instituto Superior de Engenharia de Lisboa,

Instituto Politecnico de Lisboa 1959-007 Lisboa, Portugal.

(Dated: July 13, 2020)

Abstract

We explore a class of models which can provide a common origin for the recently observed

evidence for lepton flavor universality violation in b → sl+l− decays, the dark matter (DM)

problem and the long-standing muon (g − 2) anomaly. In particular, both anomalies in the B

meson decays and the muon (g − 2) can be explained by the additional one-loop diagrams with

DM candidates. We first classify several simple models according to the new fields’ quantum

numbers. We then focus on a specific promising model and perform a detailed study of both DM

and flavor physics. A random scan over the relevant parameter space reveals that there is indeed

a large parameter space which can explain the three new physics phenomena simultaneously,

while satisfying all other flavor and DM constraints. Finally, we discuss some of the possible

new physics signatures at the Large Hadron Collider.

a dahuang@ua.ptb aapmorais@ua.ptc rasantos@fc.ul.pt

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Linking axion-like dark matter, the XENON1T excess, inflation and the tiny active

neutrino masses

H. N. Longa,b,1, ∗ D. V. Soac,1, † V. H. Binhd,1, ‡ and A. E. Carcamo Hernandeze1, §

1 a Theoretical Particle Physics and Cosmology Research Group,Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam

bFaculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnamc Faculty of Natural Sciences and Technology, Hanoi Metropolitan University,

98 Duong Quang Ham, Cau Giay, Hanoi, Vietnamd Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Ba Dinh, Hanoi, Vietnam

e Departamento de Fısica, Universidad Tecnica Federico Santa Marıa,Casilla 110-V, Valparaıso, Chile

(Dated: July 13, 2020)

We consider a renormalizable theory, which successfully explains the number of Standard Model(SM) fermion families and whose non-SM scalar sector includes an axion dark matter as well as a fieldresponsible for cosmological inflation. In such theory, the spontaneous breaking of the Peccei-Quinn(PQ) symmetry at a very large scale produces very large Majorana neutrino masses, thus allowinga natural explanation of the tiny active neutrino masses from a tree-level type I seesaw mechanism.In the theory under consideration, soft-breaking mass terms generate an axion mass consistent withthe current experimental limits. Furthermore, the theory under consideration can also successfullyaccommodates the XENON1T excess provided that the PQ symmetry is spontaneously broken atthe 1010 GeV scale.

I. INTRODUCTION

Currently, an axion is a very attractive subject in Particle Physics in both theoretical and experimental aspects [1, 2],thus providing a motivation to consider extensions of the Standard Model that include this particle in its field content.The axion is a CP-odd scalar field which arises in the solution of the strong-CP problem, and originally it is alwaysmassless particle that prevent its possibility to be a dark matter candidate. In order to generate a mass for the axion,one can consider the implementation of radiative corrections as shown in [5–7] or gravitational effects [8]. In thispaper, we present a new mechanism to generate the axion mass, which to the best of our knowledge has not beenpreviously discussed in the literature.

It is interesting to note that nowadays the axion is widely considered as a candidate of dark matter (DM)[9]. The darkmatter candidate is existed only in some beyond standard models. Among the SM extensions, the models based onthe SU(3)C × SU(3)L ×U(1)X gauge symmetries (called 3-3-1 models, for short) [10, 11] have several very interestingfeatures, some of them being, the natural explanation of the number of SM fermion families, the electric chargequantization and the solution of the strong CP problem from the PQ symmetry [12], which is automatically fulfilledin the 3-3-1 models In one of the 3-3-1 models, there exist both interesting features, namely the axion dark mattercandidate and inflaton for Early Universe [17, 18]. In the above mentioned papers, the axion gets mass only fromgravitational contribution.

It is worth mentioning that the CP-odd sector of the 3-3-1 model with axion has been considered in [17–19]. However,the rotation matrix that diagonalizes the squared mass matrix for the CP odd neutral scalar fields given in [17], whichwas obtained by Mathematica is not unitary, and thus such mixing matrix cannot be used for further studies suchcoupling constants, collider phenomenology, etc. The aim of this work is to reconsider the CP-odd scalar sector ofthe aforementioned model with the inclusion of the soft-breaking mass term, which in turn generates the mass of theaxion. Such soft-breaking mass term was not considered in [17]. Our paper is organized as follows: in Section IIwe present brief review of the model. Section III is devoted to discrete and Peccei-Quinn symmetries needed for theaxion existence. The Higgs potential and the resulting physical scalar spectrum is discussed in Section IV. We state

∗Electronic address: hoangngoclong@tdtu.edu.vn†Electronic address: dvsoa@hnmu.edu.vn‡Electronic address: vhbinh@iop.vast.ac.vn§Electronic address: antonio.carcamo@usm.cl

More Axions from Strings

Marco Gorghettoa, Edward Hardyb, and Giovanni Villadoroc

a Department of Particle Physics and Astrophysics, Weizmann Institute of Science,Herzl St 234, Rehovot 761001, Israel

b Department of Mathematical Sciences, University of Liverpool,Liverpool, L69 7ZL, United Kingdom

c Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34151, Trieste, Italy

Abstract

We study the contribution to the QCD axion dark matter abundance that is producedby string defects during the so-called scaling regime. Clear evidence of scaling violationsis found, the most conservative extrapolation of which strongly suggests a large number ofaxions from strings. In this regime, nonlinearities at around the QCD scale are shown to playan important role in determining the final abundance. The overall result is a lower boundon the QCD axion mass in the post-inflationary scenario that is substantially stronger thanthe naive one from misalignment.

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