a light scalar wimp? evidences vs indirect constraints · 95% c.l. limits on flux from dsphs...
TRANSCRIPT
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A light scalar WIMP?
Evidences vs indirect constraints
Michel H.G. Tytgat
Université Libre de Bruxelles
Belgium
October 18 2010
Max-Planck-Institut für Kernphysik – Particle & Astroparticle Physics
Heidelberg
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Based on works done in collaboration with
Chiara Arina
Sarah Andreas
Nicolas Cosme
Thomas Hambye
Fu-Sin Ling
Laura Lopez Honorez
Emmanuel Nezri
Gilles Vertongen
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There are some experimental indications of a light WIMP, M ~ few GeV
This is likely to have nothing to do with Dark Matter, but the concordance is intriguing.
Here I consider a very simple model that is (marginally) compatible with current experiments, including WMAP.
First I motivate the model, then I discuss some indirect constraints, mostly based on Fermi-LAT data
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Current direct detection indications & exclusion limits
(very briefly)
Indications:
● DAMA annual modulation
● CoGeNT events at low recoil energies
● CRESST events (Oxygen target) (still preliminary)
● CDMS-II two events, low significance
Exclusion limits:
● CDMS-Si
● Xenon 10 & Xenon 100
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Figure from Th. Schwetz-Mangold (talk at MPIK, June 2010)
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Figure from Th. Schwetz-Mangold (talk at MPIK, June 2010)
DAMA
No channeling (most likely*)
With channeling
* See Bozorgnia, Gelmini, GondoloArXiv:1006.3110 + refs therein
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Figure from Th. Schwetz-Mangold (talk at MPIK, June 2010)
CDMS-II
Only 1-sigma region
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Figure from Th. Schwetz-Mangold (talk at MPIK, June 2010)
Here,
loosely called the
«DAMA/CoGeNT region»
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Figure from Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
A zoom on the DAMA/CoGeNT region and a look at exclusion limits
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Figure from Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
A zoom on the DAMA/CoGeNT region and a look at exclusion limits
CDMS-Si
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Figure from Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
A zoom on the DAMA/CoGeNT region and a look at exclusion limits
Xenon10 (2009) (LeffMed)
CDMS-Si
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Figure from Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
A zoom on the DAMA/CoGeNT region and a look at exclusion limits
Xenon10 (2009) (LeffMin)Xenon10 (2009) (LeffMed)
CDMS-Si
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Figure from Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
A zoom on the DAMA/CoGeNT region and a look at exclusion limits
Xenon10 (2009) (LeffMin)Xenon10 (2009) (LeffMed)
CDMS-Si
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In LXe experiments, mapping of signal (ie photoelectrons PE) to Erecoil
depends on the so-called Scintillation Efficiency (Leff)
Light Dark Matter range
LeffMed
LeffMin
LeffZep (very conservative)
Problem: Leff poorly known at low recoil energiesSee Collar & McKinsey vs Xenon100 debate
Cutoff @ 1 keV
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DAMA
DAMA w/channelling
CoGeNT
LeffZepLeffMin
LeffMed
Andreas, Arina, Hambye, Ling, M.T. (arXiv:1003.2595)
4PE
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DAMA
DAMA w/channelling
CoGeNT
LeffZepLeffMin
LeffMed
Andreas, Arina, Hambye, Ling, M.T. (arXiv:1003.2595)
Prospect:1 ton-days exposure (LeffMin)
4PE
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CoGeNT
Hooper,Collar,Hall,McKinsey
Gelmini, Gondolo, Savage
Kopp, Schwetz, Zupan
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The current experimental
anomalies might have nothing to
do with Dark Matter...
Nevertheless it is fair to look
for possible explanations and
phenomenological implications
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A prejudice* against light WIMPs ?
*1 : injury or damage resulting from some judgment or action of another in disregard of one's rights; especially : detriment to one's legal rights or claims
2 a (1) : preconceived judgment or opinion (2) : an adverse opinion or leaning formed without just grounds or before sufficient knowledge b : an instance of such judgment or opinion c : an irrational attitude of hostility directed against an individual, a group, a race, or their supposed characteristics
increasing annihilationcross section
σ v ~ α²/M2
→ M ~ 10² GeV
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Light mass ~ few GeV ?
WIMP → thermal freeze-out
New mass scale!
Unrelated to known/expected new physics (?)
WMAP → σ v ~ pbarn !
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Cowsik-McLelland Lee-Weinberg Griest-Kamionkowski
A neutrino with EW interactions
Figure from Dolgov
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Why I ♥ GeV Dark Matter ?
Ωdm/Ω
b = (m
dm ndm)/(m
b n
b)≈ 5
If mdm ~ few GeV � n
dm ~ n
b
A cosmological coincidence(?)
An asymmetry in the dark sector ?
Nussinov; Barr; Kaplan;Gudnasson et al;Dodelson et al;Kitano et al;Farrar et al; Lopez Honorez, Cosme & M.T.; Zurek et al; … and many new scenarios since recently
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Lopez Honorez, Cosme & M.T. (2005)
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Figure from Lopez Honorez, Cosme & M.T. (2005)
« DM catastrophe »
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A real scalar singlet model (SM+3)
Silveira & Zee '85; McDonald '94; Burgess, Pospelov, ter Veldhuis '00; Patt,Wilczek '06; Barger et al '08;...
Introduce an ad hoc parity (with SM dof even)
S → -S
Also assume <S>=0
S is a dark matter candidate with mass
mS
2 = μS
2 + λS v2
Here, a very simple, conservative model (ie a WIMP)
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Why is this st... hum, simple model interesting?
Motivation #1: the simplest instance of Higgs portal
Motivation #2: a one-to-one correspondence between annihilation (ie WMAP) and Spin-Independent (SI)elastic scattering (ie DAMA/CoGeNT)
Motivation #3: dramatically affects Higgs physics
Motivation #4: potentially large indirect signals
→ « works », but falsiable model
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Dark Sector Visible SectorHiggsSector
e.g. Inert Doublet Model (Deshpande,Ma;Barbieri,Hall,Ryshkov)
WIMPless scalar (Feng et al)
SO(10) framework (Kadastik,Kannike, Raidal) ...
Motivation #1: an instance of Higgs portal (Patt & Wilczek)
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The most general (CP & Z2 conserving) potential
with two Higgs doublets is
Mh² = λ
1 v²
Spectrum
Inert Doublet Model
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Global custodial SU(2) symmetry if MH+= M
H0 or
MH+= M
A0
(Gérard, Herquet)
large gap ~ λ5 v²
Effectively H0 or A
0 like a
scalar singlet S
(Andreas, Hambye, T.)
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Possible embedding in UED model (Z2 is
KK-parity), but wrong spectrum...
figure from Hooper & Profumo
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Annihilation Scattering (SI)
Ratio depends only on M
S
Higgs-Nucleus coupling... large uncertainty (f ~ 0.1-0.6 @ 2σ)
f mN = <N|Σ m
q qq|N> = g
hNN v
Motivation #2: a one-to-one correspondence between annihilation and Spin-Independent (SI)elastic scattering
Low energy limit
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WMAP
S.Andreas, Th.Hambye, MT '08
DAMA
Singlet scalar
DAMA region from Pietrello & Zurek '08 (with channelling & standard halo)
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WMAP
S.Andreas, Th.Hambye, MT '08
DAMA
Singlet scalar
DAMA region from Pietrello & Zurek '08 (with channelling & standard halo)
mS
2 = μS
2 + λS v2
Not natural Need tuning :(
New mass scale?
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Singlet scalarCandidates with WMAP abundance
Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
Concordance with CoGeNT and/or DAMA
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Singlet scalardomain consistent with WMAP abundance
Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
Concordance with CoGeNT and/or DAMA
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Singlet scalardomain consistent with WMAP abundance
Andreas, Arina, Hambye, Ling & M.T. arXiv:1003.2595
Concordance with CoGeNT and/or DAMA QCD phase transition
Smaller g_eff → higher abundance → need larger coupling
Tc = 15O MeVTc = 300 MeVTc = 500 MeV
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Fitzpatrick, Hooper & Zurek
ArXiv:1003.0014
Effective operators approach
Barger, McCaskey, Shaughnessy
ArXiv:1005.3328
Complex singlet scalar
This is consistent with other recent works
Cogent & WMAP
Cogent
WMAPEffectively a real singlet scalar
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Remark : A fermion (D or M) singlet with Higgs does not work
Typically needs other channels
P-wave suppressed
Thus larger abundance
e.g. light neutralino (Bottino, Donato, Fornengo & Scopel; others)
Andreas, Hambye, M.T.
P odd initial state if S-wave
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Fitzpatrick, Hooper & Zurek
ArXiv:1003.0014
Effective operators approach
Mambrini ArXiv:1006.3318
Dirac fermion with a
light Z'
OK if use the Z' pole to enhance the annihilation cross section
Dirac DM candidate?
Cogent
WMAP
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Invisible Higgs decay at the LHC
For instance MS = 7 GeV :
For λS = 0.2 and m
higgs= 120 GeV
BR(h → SS) = 99.5%
For λS = 0.55 and m
higgs= 200 GeV
BR(h → SS) = 70%
higgs
S
S
Andreas, Hambye, M.T.
See also Burgess, Pospelov & ter Veldhuis; Barger et al;
Motivation 3: affects Higgs physics
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mhiggs
= 120 GeV mhiggs
= 180 GeV
75% < INVIS. BR. < 90 % for CoGeNT with Mhiggs @ 180 GeV
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Invisible Higgs search?
Most promising channel@ LHC is Z-boson associated production iedi-lepton + missing E
T
(Jets + missing ET is much less
Important)(Eboli & Zeppenfeld)
Remark: similar problematic forNMSSM light WIMP scenarios(Gunion, Hooper & West)
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Annihilation rate ~ ndm
2 ~ 1/mdm
2
Flux of gammas, neutrinos, positrons ➚➚
HORIZON simulationAthanassoula et al
Motivation #4: potentially « large » indirect signals
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Constraint # 1: gammas rays from dwarf spheroidal galaxies (dSph)
+ Largest galactic dark matter subhalos (we believe)
+ Low gamma-ray background
- low statistics
analysis by Fermi-LAT collaboration, 11 months of data, with 95% CL on gamma flux from Milky Way dwarf spheroidal galaxies (dSph)
● 14 best candidates dSph
● short distances (< 150 kpc), high latitudes for low background (-30° < b < 30°)
● dSph modelled as point sources
● No observation of gamma from dSph
� 95% CL limits on DM (based on NFW profile)
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Figures from Fermi-LAT; Abdo et al, arXiv:1001.4531
95% C.L. limits on flux from dSphs between 100 MeV < E < 50 GeV
Harder spectrum � stronger constaints
on fl
100% in b-bbar 100% in τ+ τ-
But only published limits for M > 30 GeV neutralino and KK-dm candidates
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New limits on the gamma ray flux from dSphs from a light scalar singlet with WMAP cross section
Our (naive) extrapolations based on Fermi-LAT data
Our predicted fluxes but tentative (e.g. energy resolution, acceptance,... not taken into account)
Andreas, Arina, Hambye, Ling, M.T. (arXiv:1003.2595)See also Fitzpatrick, Hooper & Zurek
>
>
>
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Stacked analysis → stronger limits: light candidates in b-bbar excluded @ 95% CL
CoGeNT/DAMA candidates
From the talk by Maja LLENA GARDE (Fermi-LAT) @ IDM2010
WMAP abundance
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Constraint # 2: Isotropic extragalactic gamma-ray flux
Boost factor
Figure from Ch. Arina, M.T. (2010)
Redshift z
Enhancement from first DM halos
Mean cosmic density
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Constraint # 2: Isotropic extragalactic gamma-ray flux
Boost factor
Figure from Ch. Arina, M.T. (2010)
Redshift z
Different astrophysical assumptions
Mean cosmic density
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Universe essentially transparent for E < 10 GeV gamma-rays in the Fermi-LAT window (in pink)
Observed energyObserved energy
Redshift @ emission
Universe opaque
Universe transparent
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Constraint # 2: Isotropic extragalactic gamma-ray flux
Figure from Fermi-LAT Abdo et al arXiv:1002.3603
C.Arina,MT arXiv:1007.2765
M = 10 GeV σ = 3.10-26 cm3s-1
Predicted flux,
Fig. from Ch. Arina, M.T. (2010)
EGRET
Fermi-LAT
EGRET
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Constraint # 2: Isotropic extragalactic gamma-ray fluxConstraint # 2: Isotropic extragalactic gamma-ray flux
95% CL (from no excess in any single bin)
Astrophysics uncertainty on distribution of small mass dark matter halos (dn/dM)
Further uncertainty from the choice of DM profile (here NFW)
Consistent with many other works, some pre-dating Fermi-LAT
(Abdo et al; Profumo & Tesla; Beacon et al; Yuksel et al;...)
WMAP
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Constraint # 2: Isotropic extragalactic gamma-ray fluxConstraint # 2: Isotropic extragalactic gamma-ray flux
Using the one-to-one correspondence between the annihilation and the SI scattering cross sections
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Constraint # 2: Isotropic extragalactic gamma-ray fluxConstraint # 2: Isotropic extragalactic gamma-ray flux
Using the one-to-one correspondence between the annihilation and the SI scattering cross sections
Conservative limit
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FROM ALESSANDRO CUOCO'S TALK @ IDM2010 (SEE ALSO B. ANDERSON)
Further constraints: the Diffuse Galactic Halo
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FROM ALESSANDRO CUOCO'S TALK @ IDM2010 (SEE ALSO B. ANDERSON)
Further constraints: the Diffuse Galactic Halo
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Neutrino flux from ~ GeV DM captured in the Sun
Figure from S.Andreas, Q.Swillens, M.T. arXiv:0901.1750
Xenon CDMSDAMA(pink)
Super-Kamiokande exclusion limit
Log10 (Muon
flux) per year, per km2
Generic, see also Kumar et al; Freese et al
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Limits from Pamela data on antiprotons in cosmic rays
Figure from E.Nezri, G. Vertongen, M.T. See also J. Lavalle; G. Shaughnessy et al
Med
Max
(different choice of diffusion and geometry parameters)
This is clearly excluded
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Figure from Jedamzik & Pospelov
Remark: a light WIMP could be good for something else ...
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Singlet scalar model, but quite generic results
May be consistent with CoGeNT and/or DAMA (or CRESST for that matter) and WMAP thermal abundance
Challenged (to say the least) by other direct detection experiments
Dramatic implications for Higgs search (invisible decay)
Also potentially strong indirect constraints from Fermi-LAT data, possibly excluding this (category of) models
Conclusions
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Prospects?
A light WIMP requires a new mass scale
This problem is worse for a scalar field ... New ideas?
Expect more constraints from gamma-ray observations, but also from other indirect signatures (some not worked out yet, like synchrotron radio emission)
These constraints are easely evaded by Asymmetric Dark Matter. But then how to probe this scenario?