[.4em] lecture 3: dark matter searches at hadron...

Z′-portal DM τ-portal DM Stop Searches and DM Coannihilation Singlino-Higgsino DM Homework

Lecture 3: Dark Matter Searchesat Hadron Colliders

Zhao-Huan Yu（余钊焕）ARC Centre of Excellence for Particle Physics at the Terascale,

School of Physics, the University of Melbournehttp://yzhxxzxy.github.io

Frontiers in Dark Matter, Neutrinos, and Particle PhysicsTheoretical Physics Summer School

Sun Yat-Sen University, GuangzhouJuly 27-28, 2017

Zhao-Huan Yu (Melbourne) Dark Matter Searches at Hadron Colliders July 2017 1 / 57

http://yzhxxzxy.github.io


Monojet Searches and Z ′-portal Simplified DM Models

[arXiv:1503.02931, PRD]



DM Production

g

g

bχ02

ℓ−

g qχ+

1 νℓ′

g

g

bb

qq′

ℓ+

ℓ−

χ01

χ01

νℓ′

ℓ′+

q

q

g

χ

χ

q

Social dark matterAccompanied by other new particles

Complicated decay chainsDecay products of other particles

Various final states(jets+ leptons+ /E, ...)

Maverick dark matterDM particle is the only new particle

reachable at the collision energyDirect production

Mono-X+ /E final states(monojet, mono-γ, mono-W/Z , ...)

[From Rocky Kolb’s talk]



DM Direct Production at Hadron Colliders

q

q

g

χ

χ

q

g

g

q

χ

χ

q

Monojet+ /ET

q

q

q

χ

χ

γ/Z

γ/Z

q

q

χ

χ

γ/Z

Monophoton/mono-Z + /ET

q

q

q′

χ

χ

W

W

q

q′

χ

χ

W

Mono-W + /ET

Sensitive to the DM couplings toquarks, gluons

photons, Z bosonsW± bosons



Monojet+ /ET Channel at the LHC

[GeV]χM1 10

2103

10

]2

-Nu

cle

on

Cro

ss S

ectio

n [

cm

χ

-4610

-4510

-4410

-4310

-4210

-4110

-4010

-3910

-3810

-3710

-3610

-1CMS, 90% CL, 8 TeV, 19.7 fb

-1CMS, 90% CL, 7 TeV, 5.0 fb

LUX 2013

superC

DM

S

CD

MS

lite

XENON100

COUPP 2012

SIMPLE 2012

CoGeNT 2011

CDMS II

CMS

Spin Independent

2Λ

q)µ

γq)(χµ

γχ(

Vector

3Λ4

2)νµ

a(G

sαχχ

Scalar

-1CMS, 90% CL, 8 TeV, 19.7 fb

[GeV]χM1 10

2103

10

]2

-Nu

cle

on

Cro

ss S

ectio

n [

cm

χ

-4610

-4510

-4410

-4310

-4210

-4110

-4010

-3910

-3810

-3710

-3610

-1CMS, 90% CL, 8 TeV, 19.7 fb

-1CMS, 90% CL, 7 TeV, 5.0 fb

COUPP 2012

-W+

IceCube W

SIMPLE 2012

-W+

Super-K W

CMS

Spin Dependent

2Λ

q)5

γµ

γq)(χ5

γµ

γχ(Axial-vector operator

[CMS coll., arXiv:1408.3583]

In the context of effective field theory, effectiveoperators can be used to describe interactionsbetween DM and quarks, which could induce themonojet+ /ET signal at the LHC, as well asDM-nucleus scattering signals in DM directdetection experiments

χγµχ qγµq operators: upper right plotThe 8 TeV LHC sensitivity is better than directdetection only when mχ ≲ 3 GeV

χγµγ5χ qγµγ5q operators: lower right plotThe 8 TeV LHC sensitivity is much better thandirect detection



A Little Further than Effective Operators

q

q

g

χ

χ

q

Effective operators

⇒q

Z ′

q

g

χ

χ

q

Z ′-portal simplified models

The valid range of effective field theory is limited: if the momentumtransfer in scattering is sufficient large (comparable to or even larger thanthe mediator mass), the effective operator approach would break downIn this case, simplified models involving only renormalizable operatorswould give a more reasonable description



Z ′-portal DM Simplified Models

We discussed a class of Z ′-portal simplified models, where the mediator Z ′ isa vector boson

FV model: Dirac fermion χ, vector current interactions

LFV =∑

q

gq Z ′µqγµq+ gχZ ′µχγµχ

FA model: Dirac fermion χ, axial vector current interactions

LFA =∑

q

gq Z ′µqγµγ5q+ gχZ ′µχγµγ5χ

SV model: complex scalar χ, vector current interactions

LSV =∑

q

gq Z ′µqγµq+ i gχZ ′µ[χ∗∂ µχ − (∂ µχ∗)χ]

We would like to investigate the sensitivity of the monojet+ /ET channel atfuture hadron colliders with ps = 33 TeV (VHE-LHC), 50 TeV (SPPC), and100 TeV (FCC-hh)



Event Selection in the monojet+ /ET ChannelF

raction o

f events

E ⁄ T (GeV)

pp collider, √s = 50 TeV, monojet + E ⁄ T

FA

FV

SV

Z + jets

W + jets

10-5

10-4

10-3

10-2

10-1

100

0 1000 2000 3000 4000 5000 6000

Fra

ction o

f events

E ⁄ T (GeV)

pp collider, √s = 100 TeV, monojet + E ⁄ T

FA

FV

SV

Z + jets

W + jets

10-5

10-4

10-3

10-2

10-1

100

1000 2000 3000 4000 5000 6000

Signalbenchmarkpoint:mχ = 1 TeV

mZ ′ = 5 TeV

gq = gχ = 0.1

DM production signal: pp→ Z ′(∗)(→ χχ/χχ∗) + jetsMain SM backgrounds: pp→ Z(→ νν) + jets, pp→W (→ lν) + jets

/ET > 1.6/1.8/2.6 TeV; Jet number njet ≥ 1; the leading jet j1 satisfies |η( j1)|< 2.4and pT( j1)> 1.6/1.8/2.6 TeV for ps = 33/50/100 TeV

Reject events containing > 2 jets with pT > 100 GeV and |η|< 4; a second jet isallow if it satisfies ∆ϕ( j1, j2)< 2.5 for suppressing the QCD multi-jet backgroundReject events containing isolated electrons, muons, τ-jets, and photons withpT > 20 GeV and |η|< 2.5



SPPC vs. DM Direct Detectionm

χ (G

eV

)

mZ’ (GeV)

50TeV pp collider, 3 ab-1

, FV

LUX 2013

SuperCDMS

Xenon 100

Xenon 1T

100

101

102

103

104

105

101

102

103

104

105

g q=g χ

=0.1

gq=gχ=0.3

gq=gχ=0.5

gq=gχ=1.0

mχ (G

eV

)

mZ’ (GeV)


, FA

COUPP 2012

SIMPLE 2011

PICASSO 2012

Super-K W+W

−

IceCube W+W

−

100

101

102

103

104

105

106

101

102

103

104

mχ (G

eV

)

mZ’ (GeV)


, SV

LUX 2013

SuperCDMS

Xenon 100

Xenon 1T

100

101

102

103

104

105

101

102

103

104

105

Dashed lines: 90% CL expected exclu-sion limits at the SPPC

Solid lines: 90% CL exclusion limitsfrom direct detection for

gq = gχ = 0.5

Light red region: unitarity violation forgq = gχ = 1



SPPC vs. DM Relic Densitym

Z’

(GeV

)

mχ (GeV)

50 TeV pp collider, 3 ab-1

, FV

Relic density

Collider

100

101

102

103

104

100

101

102

103

104

gq=

gχ=

0.5

gq=

gχ=

0.3

gq=

gχ=

0.1

m Z’ = 2 m χ

mZ

’ (G

eV

)

mχ (GeV)


, FA

Relic density

Collider

100

101

102

103

104

100

101

102

103

104

gq=gχ

=0.5gq=gχ

=0.3

gq=gχ=0.1

m Z’ = 2 m χ

mZ

’ (G

eV

)

mχ (GeV)


, SV

Relic density

Collider

100

101

102

103

104

100

101

102

103

104

gq=

gχ=

0.5

gq=

gχ=

0.3

gq=

gχ=

0.1

m Z’ = 2 m χ

Dashed lines: 90% CL expectedexclusion limits at the SPPC

Solid lines: observed value of theDM relic density



LHC Searches for τ-portal DM Models

[arXiv:1410.3347, PRD]



Excess of GeV Continuous Spectrum γ-rays

20 40 60 80 100

10-26

10-25

MDM @GeVD

XΣv

\@cm

3s-

1D

KRA, gNFW HΓ = 1.26L

bb Χmin2 dof = 1.44

ææ

æ

æ

ææ

æ

ææ

æ

æ

æ

æ

æ æ

æ

æ

æ æ æ

æ

æ æ

æ

æ

100 101 102-1.

0.

1.

2.

3.

4.

EΓ @GeVD

10

6

EΓ2

dF

dE

Γd

W@G

eVcm

-2

s-1

sr-

1D

MDM = 37.8 GeV

XΣ v\ = 2.10 10-26 cm3s-1

5 10 15 20 25 30

10-26

10-25

MDM @GeVDXΣ

v\@

cm3

s-1

D

KRA, gNFW HΓ = 1.26L

BRΤ = 100% Χmin2 dof = 3.4

BRΜ = 0%BRe = 0%

ææ

æ

æ

ææ

æ

ææ

æ

æ

æ

æ

æ æ

æ

æ

æ æ æ

æ

æ æ

æ

æ

100 101 102-1.

0.

1.

2.

3.

4.

EΓ @GeVD

10

6

EΓ2

dF

dE

Γd

W@G

eVcm

-2

s-1

sr-

1D

MDM = 8 GeV

XΣ v\ = 6.96 10-27 cm3s-1

[Cirelli et al., arXiv:1407.2173]

Since 2009, several groups reported an excessof continuous spectrum γ-rays in the GalacticCenter (GC) region, peaking at a few GeV aftersubtracting well-known astrophysical backgroundsin the Fermi-LAT data

Interpretation with DM annihilation into bb:

mχ ≃ 30− 40 GeV

⟨σannv⟩ ∼ 10−26 cm3 s−1

Interpretation with DM annihilation into τ+τ−:

mχ ∼ 9 GeV

⟨σannv⟩ ∼ 5× 10−27 cm3 s−1



τ-portal Simplified DM Models

φ

χ

χ

τ−

τ+

DFDM: annihilation

ψ

χ

χ∗

τ−

τ+

CSDM: annihilation

We studied four τ-portal simplified modelsinvolving a mediator with additive quantumnumbers identical to the right-handed τ−

We interpreted the GC GeV excess signal asDM annihilation into τ+τ−, and discussed howto test this interpretation at the LHC

Spin-1/2 fermion χ, spin-0 mediator ϕ:Lϕ = λϕτRχL + h.c.

DFDM model: χ is a Dirac fermionMFDM model: χ is a Majorana fermion

Spin-0 scalar χ, spin-1/2 mediator ψ:Lψ = κχτRψL + h.c.

CSDM model: χ is a complex scalarRSDM model: χ is a real scalar



DM Annihilation into τ+τ− in the Low Velocity Limit

DFDM model:12⟨σannv⟩= λ4 m2

χβτ

64π(m2ϕ+m2

χ−m2

τ)2≃ 5×10−27 cm3 s−1

mχ

9.4 GeV

2 λ

mϕ/179 GeV

4MFDM model:

⟨σannv⟩= λ4 m2τβτ

32π(m2ϕ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

λ

mϕ/93 GeV

4

Helicity suppression

CSDM model:12⟨σannv⟩= κ4 m2

τβ3τ

32π(m2ψ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

κ

mψ/93 GeV

4


RSDM model:

⟨σannv⟩= κ4 m2τβ3τ

4π(m2ψ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

κ

mψ/156 GeV

4


(βτ ≡q

1−m2τ/m

2χ ; mτ≪ mχ ≪ mϕ , mψ approximation)



DM Annihilation into τ+τ− in the Low Velocity Limit

DFDM model:12⟨σannv⟩= λ4 m2

χβτ

64π(m2ϕ+m2

χ−m2

τ)2≃ 5×10−27 cm3 s−1

mχ

9.4 GeV

2 λ

mϕ/179 GeV

4MFDM model:

⟨σannv⟩= λ4 m2τβτ

32π(m2ϕ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

λ

mϕ/93 GeV

4Helicity suppression

CSDM model:12⟨σannv⟩= κ4 m2

τβ3τ

32π(m2ψ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

κ

mψ/93 GeV


RSDM model:

⟨σannv⟩= κ4 m2τβ3τ

4π(m2ψ+m2

χ−m2

τ)2≃ 5× 10−27 cm3 s−1

κ

mψ/156 GeV


(βτ ≡q

1−m2τ/m

2χ ; mτ≪ mχ ≪ mϕ , mψ approximation)



Direct Detection

τ

φ

τ

γ

χ

χ

A

ZN

A

ZN

φ

τ

φ

γ

χ

χ

A

ZN

A

ZN

DM-nucleus scattering for DFDM(ϕ↔ψ: DM-nucleus scattering for CSDM)

SI DM-nucleus scattering cross sections in the DFDM and CSDM models:

σDFDMχN =

Z2e2B2µ2χN

πA2, σCSDM

χN =Z2e2C2µ2

χN

8πA2, µχN ≡ mχmN

mχ +mN

Form factor B ≃ − λ2e64π2m2

ϕ

h12 +

23 ln

m2τ

m2ϕ

imatches [χγµ(1− γ5)∂ νχ + h.c.]Fµν

Form factor C ≃ − κ2e16π2m2

ψ

h1+ 2

3 ln

m2τ

m2ψ

imatches (∂ µχ)(∂ νχ∗)Fµν

Unconstrained by experiments:MFDM: the leading contributioncomes from an anapole momentoperator [−χγµγ5∂

νχ + h.c.]Fµν

RSDM: the leading contributioncomes from two-loop diagramsvia exchanging two photons



Mediator Pair Production at the LHC

γ/Z

φ

φ∗

q

q

τ−

χ

χ

τ+

DFDM or MFDM

γ/Z

ψ

ψ

q

q

τ−

χ

χ

τ+

CSDM or RSDM10-2

10-1

100

101

102

103

104

100 200 300 400 500 600

Pro

du

ctio

n c

ross s

ectio

n

(fb

)

mφ or mψ (GeV)

LHC, mediator pair production

DFDM / MFDM

(scalar mediator)

CSDM / RSDM

(fermionic mediator)

8 TeV

14 TeV

As the mediators ϕ and ψ carry Q = Y = −1, theycould be produced at the LHC through Drell-Yanprocesses exchanging s-channel γ or Z , and thendecay into τ± and χWe found that the 8 TeV LHC data cannotexplore the interesting regions in these models,and went further to investigate the LHC sensitivityat ps = 14 TeV with tight τh-tagging techniques



14 TeV LHC Searches for pp→ ϕϕ∗/ψψ→ τ+τ−χχ

Fra

ction o

f events

mT2 (GeV)

LHC, 14 TeV, 2τh + E ⁄ T

Diboson

Top pair

W + jets

DFDM

MFDM

CSDM

RSDM

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 50 100 150 200 250 300

Signals：DFDM modelmϕ = 225 GeV

MFDM modelmϕ = 250 GeV

CSDM modelmψ = 300 GeV

RSDM modelmψ = 200 GeV

2τh + /ET channel: two opposite-sign tau-jet (τh);without any other particle; mT2 > 90 GeV

τℓτh + /ET channel: one τh and one light lepton(ℓ= µ, e) with opposite signs; without any otherparticle; mT2 > 90 GeV

2τℓ + /ET channel: two opposite-sign light leptons;|mℓℓ −mZ |> 10 GeV for the same-favor case;without any other particle; mT2 > 100 GeV




Fra

ction o

f events

mT2 (GeV)


Diboson

Top pair

W + jets

DFDM

MFDM

CSDM

RSDM

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 50 100 150 200 250 300

Fra

ction o

f events

mT2 (GeV)

LHC, 14 TeV, τlτh + E ⁄ T

Diboson

Top pair

W + jets

DFDM

MFDM

CSDM

RSDM

0.00

0.05

0.10

0.15

0.20

0.25

0 50 100 150 200 250











Fra

ction o

f events

mT2 (GeV)


Diboson

Top pair

W + jets

DFDM

MFDM

CSDM

RSDM

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 50 100 150 200 250 300

Fra

ction o

f events

mT2 (GeV)

LHC, 14 TeV, τlτh + E ⁄ T

Diboson

Top pair

W + jets

DFDM

MFDM

CSDM

RSDM

0.00

0.05

0.10

0.15

0.20

0.25

0 50 100 150 200 250

Fra

ction o

f events

mT2 (GeV)

LHC, 14 TeV, 2τl + E ⁄ T

Diboson

Top pair

DFDM

MFDM

CSDM

RSDM

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 50 100 150 200










Resultsλ

mφ (GeV)

Dirac fermionic DM, scalar mediator

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

100 200 300 400 500 600

LE

P

LUX

GC GeV excess

λ

mφ (GeV)

Majorana fermionic DM, scalar mediator

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

100 200 300 400 500 600

LE

P

GC GeV excess

DFDM MFDM

κ

mψ (GeV)

Complex scalar DM, fermionic mediator

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

100 200 300 400 500 600

LE

P

LUX

GC GeV excess

HL-LHC

(3000 fb-1

)

5σ

d

isco

ve

ry

95

% C

L e

xclu

sio

n

κ

mψ (GeV)

Real scalar DM, fermionic mediator

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

100 200 300 400 500 600

LE

P

GC GeV excess

HL-LHC

(3000 fb-1

)

5σ

d

isco

ve

ry

95

% C

L e

xclu

sio

n

CSDM RSDM



Stop Searches and DM Coannihilation

[arXiv:1211.2997, PRD]



Problem of the Standard Model (SM)

A ∼125 GeV SM-like Higgs boson has been discovered

The quantum correction of SM Higgs boson mass ∆m2H suffers from

quadratic divergence⇓

Hierarchy problem⇓

New physics at TeV scale(supersymmetry, extra dimension, little Higgs, ...)



Stops in Supersymmetric (SUSY) Models

The lighter stop t1 is probably reachable in early LHC searches.In order to cancel the large radiative corrections to mH from the topquark loop without fine tuning, the stops t1,2 need to be light enough.t1 can be the lightest colored supersymmetric particle due to the largetop Yukawa coupling and large mass splitting terms in many SUSYmodels.

In the following work, the direct production of t1 t∗1 pairs at the LHC isconsidered: pp→ t1 t∗1 + jets

m t1[GeV] 200 400 600

7TeV, σNLO [fb] 11837 205 128TeV, σNLO [fb] 17296 342 23



Stop Direct Searches

[GeV]1t

~m200 250 300 350 400 450 500 550 600 650

10

r¾+mt

< m

1t~m

150 200 250 300 350 400 450 50

)1

0r¾ m×

= 2

1±r¾ ( m

1±r¾+m

b < m1t~m

( = 106 GeV)1±r¾ > m

1

0r¾

m

< 106 GeV 1±r¾ m

( = 150 GeV)1±r¾ > m

1

0r¾

m

-10)

1t~ =

m1±

r¾

( m1±

r¾

> m

10

r¾ m

[GeV

]10 r¾

m

0

50

100

150

200

250

300

350 =8 TeVs -1 = 13 fbintL

1

0r¾

m× = 2 ±

1rm

-1 = 13 fbintL - 10 GeV

1t~ = m±

1rm

-1 = 13 fbintL

= 150 GeV±

1rm

-1 = 13 fbintL = 106 GeV±

1rm

-1 = 4.7 fbintL

-1 = 4.7 fbintL -1 = 13 fbintL

ATLAS Preliminary

Status: December 2012

=7 TeVs -1 = 4.7 fbintL1L ATLAS-CONF-2012-166-1L ATLAS-CONF-2012-1662L ATLAS-CONF-2012-1671L ATLAS-CONF-2012-166

0L [1208.1447], 1L [1208.2590], 2L [1209.4186]2L [1208.4305], 1-2L [1209.2102]--1-2L [1209.2102]

production1t~1t

~

10

r¾+(*) WA1±r¾,

1±r¾ b+A 1t

~10

r¾ t A1t~

10

r¾ t A1t~

= 106 GeV±1

r, m

1±r¾ b+A 1t

~

= 150 GeV±1

r, m

1±r¾ b+A 1t

~

- 10 GeV1t

~ = m±1

r, m

1±r¾ b+A 1t

~

10

r¾ m× = 2 ±

1r

, m1±r¾ b+A 1t

~

Observed limits)theomObserved limits (-1

Expected limits

Assuming some simplified models in which stops can be easily detectedExcluding stops up to ∼ 580 GeV



Dark Matter (DM)

Not to violate baryon number B or lepton number L

(proton decay, flavor physics constraints)⇓

R-parity conserved SUSY [PR = (−1)3(B−L)+2s]⇓

The lightest SUSY particle (LSP) is stable.⇓

If the LSP is electrically neutral, such as χ01 , it would be an attractive

candidate for non-baryonic dark matter.



DM Relic Density

ΛCDM model fitted by 7-year WMAP data: [Ap. J. Suppl. 192, 16 (2011)]

ΩCDMh2 = 0.1109, Ωbaryonh2 = 0.02258, ΩΛ = 0.734

(Cold DM ∼ 21.1%, baryons ∼ 4.3%, dark energy ∼ 74.6%)

For thermal produced DM, ΩCDM∝ ⟨σannv⟩−1.

In many SUSY models, most likely the lightest neutralino χ01 is the LSP.

However, the sfermion exchange process χ01 χ

01 → f f has the helicity

suppression issue. The self-annihilation cross section σann of χ01 is

generally not large enough to yield the observed relic density ΩCDM.

Additional mechanisms are needed (resonance, coannihilation, ...).



CMSSM Case

100 1000 2000

0

1000

2000

100 1000 2000

0

1000

2000

m0 (

GeV

)

m1/2 (GeV)

tan β = 50 , µ > 0 (A0 = 0)

¬

®

noEW

SB

stau LSP

[Ellis, Olive, Sandick, arXiv:0704.3446]

¬ Higgs funnel region2mχ0

1≃ mA0 or mh0 or mH0

χ01 annihilates via a resonance

Focus point regionχ0

1 is a bino-higgsino orbino-wino mixturemχ0

1∼ mχ±1 or mχ0

2

χ01 coannihilates with χ±1 or χ0

2

® Sfermion coannihilation regionmχ0

1∼ mτ1

or m t1

χ01 coannihilates with τ1 or t1



Coannilation Scenarios

In general, in order to yield the desired dark matter relic density bycoannihilation mechanism, the mass of the next-to-lightest SUSY particle(NLSP) mNLSP should satisfies

mNLSP −mχ01

mχ01

≲ 20%.

[Profumo, Yaguna, arXiv:hep-ph/0407036]

In this work, we study 3 coannihilation scenarios with a light stop.1 t1-χ0

1 coannihilation: mχ01∼ m t1

2 χ±1 -χ01 coannihilation: mχ0

1∼ mχ±1 < m t1

3 τ1-χ01 coannihilation: mχ0

1∼ mτ1

< m t1



MC Simulation

Credit: Frank Krauss

Hard process⇑

MadGraph5

MLM matching

Parton shower⇑

Pythia 6.4⇓

Hadronization & decay

PGS4 ⇒ Detector simulation

Prospino2, MCFM ⇒ NLO K-factorZhao-Huan Yu (Melbourne) Dark Matter Searches at Hadron Colliders July 2017 27 / 57


Scenario 1: t1-χ01 Coannihilation

The lighter stop t1 is the NLSP: mχ01∼ m t1

t1 decay channels: t1→ tχ01 , bW χ0

1 , cχ01 , f f ′bχ0

1For mχ0

1+mc < m t1

< mχ01+mb +mW , assume t1→ cχ0

1 (100%).

t1t∗1

p

p

c (soft)

χ0

1

χ0

1

q/g

c (soft)

LHC searching channel: monojet + /ET

SM backgrounds: Z(→ νν) + jets, W (→ ℓν) + jets, ...



t1-χ01 Coannihilation: t1→ cχ0

1

m∼ χ

10

(Ge

V)

m∼t1

(GeV)

ATLAS 4.7 fb-1

, 95% CL, SR1

ATLAS 4.7 fb-1

, 95% CL, SR2

ATLAS 4.7 fb-1

, 95% CL, SR3

ATLAS 4.7 fb-1

, 95% CL, SR4

50

100

150

200

250

300

50 100 150 200 250 300

m∼t 1

= m∼χ 10 +

m c

m∼t 1

= m∼χ 10 +

m W + m b

mass diff. 20%

CDF 2.6 fb

-1 , 95% C

L

LEP

ATLAS 7TeV, 4.7fb−1, monojet + /ET

[arXiv:1210.4491]

Analysis instance:(ATLAS Signal Region 2)Lepton veto/ET > 220GeVJet 1: pT > 220GeV, |η|< 2Jet 3: pT < 30GeV∆ϕ( j2, /ET) > 0.5

⇓SM bkg: 8800± 400Observed: 8631σBSM

vis < 170 fb (95% CL)

(σvis ≡ σ · A · ε= production cross section× acceptance× efficiency)




1

m∼ χ

10

(Ge

V)

m∼t1

(GeV)

LHC √s = 8 TeV, monojet + E ⁄ T, 20 fb-1

S/√ B = 5 (37.9 fb)

S/√ B = 3 (22.7 fb)

50

100

150

200

250

300

350

400

150 200 250 300 350 5

10

20

50

100

200

Exp

ecte

d v

isib

le c

ross s

ectio

n

σ ⋅

A ⋅

ε (

fb)

m∼t 1 = m

∼χ 10 + m c

m∼t 1 = m

∼χ 10 + m W

+ m b

LHC 8TeV, 20 fb−1

Kinematic cuts:Lepton veto/ET > 300GeVJet 1: pT > 150GeV,

|η|< 2.4Jet 3: pT < 50GeV∆ϕ( j1, j2) < 2.5

⇓SM bkg: 22944(13939 Z(→ νν) + jets, 9005 W (→ ℓν) + jets)

⇓σBSM

vis < 22.7fb for S/p

B < 3, σBSMvis < 37.9fb for S/

pB < 5




1

m∼ χ

10

(Ge

V)

m∼t1

(GeV)

ATLAS 7 TeV, 4.7 fb-1

, 95% CL

CMS 7 TeV, 5.0 fb-1

, 95% CL

LHC 8 TeV, 20 fb-1

, S/√ B = 5

LHC 8 TeV, 20 fb-1

, S/√ B = 3

50

100

150

200

250

300

350

50 100 150 200 250 300 350

m∼t 1

= m∼χ 1

0 + m c

m∼t 1

= m∼χ 1

0 + m W

+ m b

m∼t 1 = 1.2 m

∼χ 10

CDF 2.6 fb

-1

LEP

For “coannihilation region” (m t1< 1.2mχ0

1),

7 TeV, ∼ 5 fb−1 → m t1≳ 150− 220GeV (95% CL)

8 TeV, 20 fb−1 → m t1≳ 270− 340GeV (S/

pB < 3)



Scenario 2: χ±1 -χ01 Coannihilation

χ01

χ01

t1

t∗1

p

p

χ+1

b

χ−

1

b

f1 (soft)

f2 (soft)

f3 (soft)

f4 (soft)

The lighter chargino χ±1 is the NLSP: mχ01∼ mχ±1 < m t1

Fixing (mχ±1 −mχ01)/mχ0

1= 10%, for mb +mχ±1 < m t1

< mχ01+mt ,

assume t1→ bχ±1 (100%) and χ±1 → f f ′χ01 (100%).

LHC searching channel: 1-2 b-jets + /ET

SM backgrounds: top pair, Z/W + heavy flavors, single top, ...



χ±1 -χ01 Coannihilation: t1→ bχ+1 , χ+1 → f f ′χ0

1

ATLAS 7 TeV, 2 b-jets + E ⁄ T, 4.7 fb-1

(m∼χ1

± = 1.1 m∼χ1

0)

SR2, 2.29 fb (95% CL)

150 200 250 300 350 400

m∼t1 (GeV)

100

150

200

250

300

350

400

m∼ χ

1±

(Ge

V)

0.02

0.05

0.2

0.5

2

5

20

0.01

0.1

1

10

Exp

ecte

d v

isib

le c

ross s

ectio

n

σ ⋅ A

⋅ ε

(f

b)

m∼t 1

= m∼χ 1

± + m b

m∼t 1

= m

∼χ 10 +

m t

ATLAS 7TeV, 4.7 fb−1, 2b-jets + /ET

[ATLAS-CONF-2012-106]

Analysis instance:(ATLAS Signal Region 2)Lepton veto/ET > 200GeVnb-jet = 2 (pT > 60GeV)Jet 3: pT < 50GeV/ET/meff > 0.25mCT > 100GeV∆ϕ( j1,2, /ET) > 0.4

⇓SM bkg: 27± 7Observed: 20σBSM

vis < 2.29fb (95% CL)

(The contransverse mass mCT defined as m2CT = (E

j1T + E j2

T )2 − (p j1

T − p j2T )

2)




1

CMS 7 TeV, b-jets + E ⁄ T, 4.98 fb-1

(m∼χ1

± = 1.1 m∼χ1

0)

1BL, 20.6 fb (95% CL)

140 160 180 200 220 240 260 280 300 320

m∼t1 (GeV)

100

150

200

250

300

m∼ χ

1±

(Ge

V)

2

5

20

50

10

Exp

ecte

d v

isib

le c

ross s

ectio

n

σ ⋅ A

⋅ ε

(f

b)

m∼t 1

= m∼χ 1

± + m b

m∼t 1

= m∼χ 1

0 + m t

CMS 7TeV, 4.98 fb−1, b-jets + /ET

[arXiv:1208.4859]

Analysis instance:(CMS Signal Region 1BL)Lepton veto/ET > 250GeVHT > 400GeVnjet ≥ 3 (pT > 50GeV)nb-jet ≥ 1 (pT > 30GeV)∆ϕmin > 4.0

⇓SM bkg: 477± 26± 38Observed: 478σBSM

vis < 20.6 fb (95% CL)




1

dN

/dm

jjj

(Eve

nts

/ G

eV

)

mjjj (GeV)

LHC √s = 8 TeV, ≥1 b-jets + E ⁄ T, 20 fb-1

(m∼χ1± = 1.1 m∼χ1

0)

top pair

Z

W

single top(m~

t1, m~χ1

±) = (260, 100)

(m~t1

, m~χ1±) = (250, 245)

10-2

10-1

100

101

102

0 200 400 600 800 1000

LHC 8TeV, 20 fb−1

Kinematic cuts:Lepton veto/ET > 200GeVHT > 300GeVnjet ≥ 3 (pT > 60GeV)nb-jet ≥ 1 (pT > 30GeV)∆ϕ( j1,2,3, /ET) > 0.4m j j j /∈ (130, 200)GeV

(Pick up a pair of jets with m j j > 60GeV and smallest ∆R, and m j j j is the invariantmass of this pair of jets and a third jet which is closest to them.)m j j j /∈ (130, 200)GeV rejects 47% (31%) of top pair (single top) events,while only rejects 20% of stop events for (m t1

, mχ±1 ) = (260, 100)GeV.




1

LHC √s = 8 TeV, ≥1 b-jets + E ⁄ T, 20 fb-1

(m∼χ1± = 1.1 m∼χ1

0)

S/√ B = 5 (14.0 fb)

S/√ B = 3 (8.4 fb)

150 200 250 300 350 400 450

m∼t1

(GeV)

100

150

200

250

300

350

400

450

m∼ χ

1± (

Ge

V)

0.5

2

5

20

50

100

1

10

Exp

ecte

d v

isib

le c

ross s

ectio

n

σ ⋅

A ⋅

ε (

fb)

m∼t 1

= m∼χ 1

± + m b

m∼t 1

= m

∼χ 10 +

m t

SM bkg: 3132(2269 top pair390 Z + heavy flavor353 W + heavy flavor120 single top)

σBSMvis < 8.4 fb for S/

pB < 3, σBSM

vis < 14.0 fb for S/p

B < 5




1

m∼ χ

1± (

Ge

V)

m∼t1

(GeV)


, 1BL, 95% CL


, mCT > 100 GeV, 95% CL


, SR3a, 95% CL


, SR2, 95% CL

LHC 8 TeV, 20 fb-1

, ≥1 b-jets + E ⁄ T, S/√ B = 5

LHC 8 TeV, 20 fb-1

, ≥1 b-jets + E ⁄ T, S/√ B = 3

100

150

200

250

300

350

400

450

150 200 250 300 350 400 450

m∼t 1

= m∼χ 1

± + m b

m∼t 1

= m∼χ 1

0 + m t

m∼χ1± = 1.1 m∼χ1

0

7 TeV, ∼ 5 fb−1 → exclusion up to m t1≃ 380GeV (95% CL)

8 TeV, 20 fb−1 → exclusion up to m t1≃ 430GeV (S/

pB > 3)



Scenario 3: τ1-χ01 Coannihilation

χ01

χ01

t1

t∗1

p

p

τ+1

b

τ−1

b

ντ

ντ

τ+ (soft)

τ− (soft)

The lighter stau τ±1 is the NLSP: mχ01∼ mτ1

< m t1

Fixing (mτ1−mχ0

1)/mχ0

1= 10%, for mb +mτ1

< m t1< mχ0

1+mt ,

assume t1→ bτ+1ντ (100%) and τ±1 → τ±χ01 (100%).

LHC searching channel: 1-2 b-jets + /ET



τ1-χ01 Coannihilation: t1→ bτ+1ντ, τ

+1 → τ+χ0

1

m∼ τ 1

(G

eV

)

m∼t1

(GeV)


, 1BL, 95% CL


, SR3a, 95% CL

LHC 8 TeV, 20 fb-1

, ≥1 b-jets + E ⁄ T, S/√ B = 5

LHC 8 TeV, 20 fb-1

, ≥1 b-jets + E ⁄ T, S/√ B = 3

100

150

200

250

300

350

400

150 200 250 300 350 400

m∼t 1

= m∼τ 1

+ m b

m∼t 1

= m∼χ 1

0 + m t

m∼τ1 = 1.1 m∼χ1

0

The neutrinos ντ(ντ) take away some energy so that b-jets become soft.

7 TeV, ∼ 5 fb−1 → exclusion up to m t1≃ 220GeV (95% CL)

8 TeV, 20 fb−1 → exclusion up to m t1≃ 370GeV (S/

pB > 3)



LHC Searches for Singlino-Higgsino DM in the NMSSM

[arXiv:1606.02149, PRD]



Motivation

Shortages of the Standard Model (SM)Radiative correction to the Higgs mass term ⇒ hierarchy problemNo cold dark matter (DM) candidate

Supersymmetry (SUSY) and R-parity conservationElegant solution to the hierarchy problemLightest supersymmetric particle (LSP) ⇒ DM candidate

No evidence of superpartners in LHC Run 1 dataPush gluino and squark mass limits up to ≳O(1) TeVElectroweak (EW) production rates are much lower; m∼O(100) GeV EWsuperpartners could hide in Run 1 searches

LHC Run 2 and further searches are promising to directly probean O(100) GeV-scale neutralino-chargino sector



Motivation



No evidence of superpartners in LHC Run 1 dataPush gluino and squark mass limits up to ≳O(1) TeV

Electroweak (EW) production rates are much lower; m∼O(100) GeV EWsuperpartners could hide in Run 1 searches




Motivation



No evidence of superpartners in LHC Run 1 dataPush gluino and squark mass limits up to ≳O(1) TeVElectroweak (EW) production rates are much lower; m∼O(100) GeV EWsuperpartners could hide in Run 1 searches




Next-to-Minimal Supersymmetric Standard Model (NMSSM)

No explanation for why µ is of the same order of the SUSY breakingscale in the Minimal Supersymmetric Standard Model (MSSM): µ-problem

⇓Introducing a singlet chiral superfield S in the NMSSM: µeff = λvs

Z3-invariant (scale-invariant) superpotential: WMSSM +λSHuHd +κS3/3

Soft breaking terms in the Higgs sector:Vsoft = m2

Hu|Hu|2 +m2

Hd|Hd |2 +m2

S |S|2 +λAλSHuHd +κAκS

3/3+ h.c.

Higgs and higgsino sectors are determined by λ, κ, Aλ, Aκ, µeff, tanβ ≡ vu/vdNeutralino mass matrix for the gauge basis (B, W 0, H0

d , H0u , S):

MN =

M1 0 −g1vd/

p2 g1vu/

p2 0

M2 g2vd/p

2 −g2vu/p

2 00 −µeff −λvu

0 −λvd2κvs



Next-to-Minimal Supersymmetric Standard Model (NMSSM)

No explanation for why µ is of the same order of the SUSY breakingscale in the Minimal Supersymmetric Standard Model (MSSM): µ-problem

⇓Introducing a singlet chiral superfield S in the NMSSM: µeff = λvs

Z3-invariant (scale-invariant) superpotential: WMSSM +λSHuHd + κS3/3

Soft breaking terms in the Higgs sector:Vsoft = m2

Hu|Hu|2 +m2

Hd|Hd |2 +m2

S |S|2 +λAλSHuHd + κAκS

3/3+ h.c.

Higgs and higgsino sectors are determined by λ, κ, Aλ, Aκ, µeff, tanβ ≡ vu/vdNeutralino mass matrix for the gauge basis (B, W 0, H0

d , H0u , S):

MN =

M1 0 −g1vd/

p2 g1vu/

p2 0

M2 g2vd/p

2 −g2vu/p

2 00 −µeff −λvu

0 −λvd2κvs



Simplified Scenarios for the Neutralino-chargino Sector

Singlino-dominated LSP χ01 ∼ S ⇒ different phenomenology from MSSM’s

Simplified scenarios with split spectraSinglino-Bino Scenario (2κvs < M1≪ M2,µeff): χ0

1 ∼ S, χ02 ∼ B

Observed DM relic density ⇒ mχ01∼O(10) GeV

Very low production rates for χ01 χ

02 and χ0

2 χ02 at the LHC

Singlino-Wino Scenario (2κvs < M2≪ M1,µeff): χ01 ∼ S; χ0

2 , χ±1 ∼ W

Moderate χ02 χ±1 and χ+1 χ−1 production rates

LHC sensitivity is similar to the bino-wino scenario in the MSSM

Singlino-Higgsino Scenario (2κvs < µeff≪ M1, M2): χ01 ∼ S; χ0

2,3, χ±1 ∼ H

Higgsino components of χ01 help satisfy the observed relic density

Lower χ02,3χ

±1 and χ+1 χ−1 rates compared with the singlino-wino scenario

Previous studies on this scenario focused on LHC [Ellwanger, 1309.1665;Kim & Ray, 1405.3700] and IceCube [Enberg et al., 1506.05714] searches



Parameter Scan

For the singlino-higgsino scenario, we perform a random parameter scan upon

100 GeV ≤ µeff ≤ 600 GeV −1 TeV ≤ Aκ ≤ 0 100 GeV ≤ Aλ ≤ 10 TeV

1≤ tanβ ≤ 50 0.05≤ λ≤ 0.7 0.05≤ κ/λ≤ 0.4

The condition κ/λ≤ 0.4 is imposed for ensuring χ01 ∼ S

Set M1 = M2 = 2 TeV and other dimensional parameters to be 5 TeV

NMSSMTools 4.6 and micrOMEGAs 3 are employed for calculating mass spectra,relic density, and other observable. The following constraints are imposed.

DM relic density: Ωχ01h2 < 0.131

Higgs: an SM-like Higgs with mh = 122− 128 GeV; current Higgs boundsLEP bounds: mχ±1 > 103.5 GeV; Γ inv

Z < 2 MeV

Muon g − 2: within the 3σ deviation −5.62× 10−11 < aNMSSMµ

< 5.54× 10−9

B physics bounds: 1.7× 10−9 < BR(Bs → µ+µ−)< 4.5× 10−9;0.85× 10−4 < BR(B+→ τ+ν)< 2.89× 10−4; 2.99× 10−4 < BR(Bs → Xsγ)< 3.87× 10−4



Relic Density Ωχ01h2 and Singlino Component |N15|2

Ω h

2

mχ~

10 (GeV)

Planck

10-5

10-4

10-3

10-2

10-1

100

0 50 100 150 200 250 300 350 400 450 500

N1

52

mχ~

10 (GeV)

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

10 100 1000

Z boson resonanceSM-like Higgs resonance

All points pass the above constraints; red points for 0.107< Ωχ01h2 < 0.131

mχ01∼ 45 GeV and ∼ 60 GeV: resonance enhancements of the Z boson and

the SM-like Higgs boson for χ01 χ

01 annihilation

mχ01≳ 70 GeV: smaller |N15|2 and sizable Higgsino components



Decay Patterns of χ02 and χ0

3B

ran

ch

ing

ra

tio

mχ~

20 (GeV) − mχ

~

10 (GeV)

Br(χ~

20 → χ

~

10 Z)

Br(χ~

20 → χ

~

10 h1)

Br(χ~

20 → χ

~

10 h2)

Br(χ~

20 → χ

~

10 a1)

0.2

0.4

0.6

0.8

1

1.2

50 100 150 200 250 300 350 400 450 500

m h1 ≥ 122

m h1 < 122

χ02 decay pattern

Bra

nch

ing

ra

tio

mχ~

30 (GeV) − mχ

~

10 (GeV)

Br(χ~

30 → χ

~

10 Z)

Br(χ~

30 → χ

~

10 h1)

Br(χ~

30 → χ

~

10 h2)

Br(χ~

30 → χ

~

10 a1)

0.2

0.4

0.6

0.8

1

1.2

50 100 150 200 250 300 350 400 450 500

m h1 ≥ 122

m h1 < 122

χ03 decay pattern

χ02 decay: χ0

2 → χ01 Z is typically dominant

χ03 decay: χ0

3 → χ01 Z , χ0

3 → χ01 h1, and χ0

3 → χ01 h2 are significant



Benchmark Points

BP1 BP2 BP3λ, κ 0.091, 0.016 0.270, 0.100 0.368, 0.144

tanβ , µeff (GeV) 39.6, 163.3 35.1, 121.3 35.6, 121.0Aκ (GeV), Aλ (TeV) −35.9, 8.94 −173.4, 3.79 −8.77, 4.43

mχ01

(GeV) 59.6 77.0 71.7mχ0

2, mχ0

3, mχ±1 (GeV) 169, 173, 170 134, 146, 126 137, 160, 126

mh1, mh2

, ma1(GeV) 46.0, 126, 55.8 23.0, 125, 153 95.3, 125, 38.7

|N13|2 + |N14|2, |N15|2 1.3%, 98.7% 33.2%, 66.8% 43.5%, 56.4%Ωχ0

1h2 0.120 0.059 0.067

BR(χ02 → χ0

1 X ) Z 98.7% h1 84.4%, qq 10.6%a1 98.6%

ℓ+ℓ− 3%, vℓ vℓ 3%

BR(χ03 → χ0

1 X )Z 97.1%

h1 100% a1 73.2%, qq 14%a1 2.7% ℓ+ℓ− 2%, vℓ vℓ 4%

BR(h1/a1→ bb/τ+τ−) / h1→ bb 91.8% a1→ bb 91.8%h1→ τ+τ− 7.3% a1→ τ+τ− 7.7%



LHC Searches

χ±1

χ02,3

W±

Z

p

p

ℓ′±

νℓ′/νℓ′

χ01

χ01

ℓ−

ℓ+

3ℓ+ /ET signature

χ−1

χ+1

W−

W+

p

p

ℓ′−

νℓ′

χ0

1

χ0

1

νℓ

ℓ+

2ℓ+ /ET signature

We consider pp→ χ02,3χ

±1 and pp→ χ+1 χ−1 production at the LHC for the

survived parameter points in the singlino-higgsino scenarioMC simulation: MadGraph 5 + PYTHIA 6 + Delphes 3

↓MLM matching ATLAS setup



3ℓ+ /ET Channelevents

/ (

GeV

fb

-1 )

LHC , √s = 14 TeV, 3 leptons

10-4

10-3

10-2

10-1

100

101

Fra

ction

mSFOS (GeV)

W Z

Z Z

BP1

BP2

BP3

0

0.2

0.4

0.6

0 50 100 150 200 250 300

events

/ (

GeV

fb

-1 )


10-4

10-3

10-2

10-1

100

101

Fra

ction

mT (GeV)

W Z

Z Z

BP1

BP2

BP3

0

0.1

0.2

0 50 100 150 200 250 300

Main backgrounds: W Z + jets and Z Z + jets productionSelection cuts at ps = 14 TeV: exact 3 charged leptons ℓ (ℓ= e,µ) withpT > 20 GeV and |η|< 2.5; no b-jet with pT > 30 GeV and |η|< 2.5;|mSFOS −mZ |< 10 GeV; /ET > 50 or 100 GeV; mT > 100 GeV

(mSFOS is the invariant mass of a same-flavor opposite-sign (SFOS) lepton pair. Transversemass mT ≡q

2(pℓT /ET − pℓT · /pT) with ℓ the one not forming the SFOS lepton pair.)



2ℓ+ /ET Channelevents

/ (

GeV

fb

-1 )


10-3

10-2

10-1

100

101

Fra

ction

mSFOS (GeV)

W Z

W W

Z Z

tt−

BP1

BP2

BP3

0

0.2

0.4

0.6

0 50 100 150 200

events

/ (

GeV

fb

-1 )


10-3

10-2

10-1

100

101

102

103

Fra

ction

mT2 (GeV)

W Z

W W

Z Z

tt−

BP1

BP2

BP3

0.2

0.4

0 50 100 150 200 250 300

Main backgrounds: t t + jets, WW + jets, W Z + jets, and Z Z + jets productionSelection cuts at ps = 14 TeV: exact 2 opposite-sign charged leptons withpℓ1

T > 30 GeV, pℓ2T > 20 GeV, and |η|< 2.5; |mSFOS −mZ |> 10 GeV;

no jet with pT > 30 GeV and |η|< 2.5; mT2 > 90, 120, or 150 GeV

(Stransverse mass mT2 ≡ minp1

T+p2T=/pT

max[mT(pℓ1T ,p1

T), mT(pℓ2T ,p2

T)].)



Cut Flows

3ℓ+ /ET channel at ps = 14 TeV

W Z Z Z BP1 BP2 BP3σ σ σ S σ S σ S

Basic cuts 105 17.3 6.39 9.77 0.021 0.033 0.060 0.095/ET > 50 GeV 37.2 1.51 4.11 10.9 0.008 0.023 0.034 0.094mT > 100 GeV 1.22 0.06 1.60 16.3 0.004 0.058 0.014 0.212

2ℓ+ /ET channel at ps = 14 TeV

W Z Z Z WW t t BP1 BP2 BP3σ σ σ σ σ S σ S σ S

Basic cuts 88.8 22.3 1798 8930 16.8 2.79 9.75 1.62 12.7 2.12Jet veto 35.8 7.25 848 253 8.23 4.20 5.42 2.77 6.86 3.50

mT2 > 90 GeV 0.24 0.32 0.48 0.98 0.58 6.21 0.05 0.61 0.13 1.48

(σ in fb; S ≡ S/p

B + S calculated with an integrated luminosity of 300 fb−1)



(Expected) Exclusion at 95% CLm

χ~20 (

Ge

V)

mχ~10 (GeV)

LHC, three leptons

m χ~ 20=m χ~ 1

0+ m Z

√s = 14 TeV, 300 fb-1

√s = 13 TeV, 30 fb-1

√s = 8 TeV, 20 fb-1

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400

3ℓ+ /ET channel

mχ~

20 (

Ge

V)

mχ~10 (GeV)

LHC, two leptons

m χ~ 20=m χ~ 1

0+ m Z

√s = 14 TeV, 300 fb-1

√s = 13 TeV, 30 fb-1

√s = 8 TeV, 20 fb-1

100

200

300

400

500

600

0 50 100 150 200 250 300 350 400

2ℓ+ /ET channel

Red/blue/green points: ps = 8/13/14 TeV with 20/30/300 fb−1 data8 TeV results are recasted from Run 1 analyses [ATLAS, 1402.7029, 1403.5294]

3ℓ+ /ET channel at 14 TeV: up to mχ02 ,χ±1 ∼ 420 GeV

2ℓ+ /ET channel at 14 TeV: up to mχ02 ,χ±1 ∼ 500 GeV

Some points with mχ02−mχ0

1≲ mZ are hard to probe due to soft final states



Spin-Independent (SI) DM-Nucleus Scattering

σS

Ip (

cm

2)

mχ~

10 (GeV)

XENON1T

LUX

10-52

10-50

10-48

10-46

10-44

10-42

10-40

10-38

10 100 1000

ξσS

Ip (

cm

2)

mχ~10 (GeV)

XENON1T

LUX

10-52

10-50

10-48

10-46

10-44

10-42

10-40

10-38

10 100 1000

In the singlino-higgsino scenario, the SI DM-nuclei scattering is mediated by h1 and h2

Resonance enhancement for freeze-out⇓

Small higgsino components in χ01⇓

Small scattering cross section

90% CL exclusion limits: LUX [1310.8214],XENON1T expected for 2 t · yr [1512.07501]

Red/blue/green points: 8/13/14 TeV LHC⊡ BP1 · BP2 · BP3

Define ξ=min(1,Ωχ01h2/0.107) to take

into account the possibility that χ01 just

contributes a fraction of dark matter −→



Spin-Independent (SI) DM-Nucleus Scattering

σS

Ip (

cm

2)

mχ~

10 (GeV)

XENON1T

LUX

10-52

10-50

10-48

10-46

10-44

10-42

10-40

10-38

10 100 1000

ξσS

Ip (

cm

2)

mχ~10 (GeV)

XENON1T

LUX

10-52

10-50

10-48

10-46

10-44

10-42

10-40

10-38

10 100 1000

In the singlino-higgsino scenario, the SI DM-nuclei scattering is mediated by h1 and h2

Resonance enhancement for freeze-out⇓

Small higgsino components in χ01⇓

Small scattering cross section

90% CL exclusion limits: LUX [1310.8214],XENON1T expected for 2 t · yr [1512.07501]


Define ξ=min(1,Ωχ01h2/0.107) to take

into account the possibility that χ01 just

contributes a fraction of dark matter −→Zhao-Huan Yu (Melbourne) Dark Matter Searches at Hadron Colliders July 2017 53 / 57


Spin-Dependent (SD) DM-nucleus Scattering

σS

Dp (

cm

2)

mχ~

10 (GeV)

IceCube

PICO-2L

PICO-60

LZ

10-44

10-43

10-42

10-41

10-40

10-39

10-38

10 100 1000

ξσS

Dp (

cm

2)

mχ~10 (GeV)

IceCube

PICO-2L

PICO-60

LZ

10-44

10-43

10-42

10-41

10-40

10-39

10-38

10 100 1000

The Z-mediated SD DM-nuclei scatteringcross section σSD is typically larger thanσSI by ∼ 2− 6 orders of magnitude, but theexperimental constraints are quite weak

90% CL exclusion limits:PICO [1503.00008, 1510.07754]

LZ expected for 5600 t · day [1509.02910]

IceCube search for νµ from χ01 χ

01 → t t

in the center of the Sun [1601.00653]

Introducing ξ will weaken the constraints −→




DM Annihilation

Annih

ilation b

ranchin

g fra

ction

mχ~

10

W+ W

-

Z Z

tt−

bb-

Z h1

Z h2

a1 h1

a1 h2

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300 350 400 450 500

⟨σa

nn v

⟩ (c

m3 s

-1)

mχ~

10 (GeV)

-

-

Fermi bb

CTA bb

10-34

10-32

10-30

10-28

10-26

10-24

10 100 1000

p-wave annihilation is important at the freeze-out epoch, but becomes negligible for today’snonrelativistic DM relevant to indirect detection

Nonrelativistic χ01 χ

01 annihilation

mχ01≲ mt : χ0

1 χ01 → bb or a1h1 dominant

with ⟨σannv⟩ ∼O(10−31 − 10−27) cm3/s

mχ01≳ mt : χ0

1 χ01 → t t dominant with

canonical ⟨σannv⟩ ∼O(10−26) cm3/s

95% CL exclusion limits for χ01 χ

01 → bb:

Fermi-LAT γ-ray observation of dwarf galaxiesfor 6 years [1503.02641], expected CTA γ-rayobservation of GC vicinities for 100 h [1208.5356]




Indirect Detection: the ξ2 Factor


⟨σa

nn v

⟩ (c

m3 s

-1)

mχ~

10 (GeV)

-

-

Fermi bb

CTA bb

10-34

10-32

10-30

10-28

10-26

10-24

10 100 1000

Without the ξ2 factorξ2

⟨σa

nn v

⟩ (c

m3 s

-1)

mχ~10 (GeV)

-

-

Fermi bb

CTA bb

10-34

10-32

10-30

10-28

10-26

10-24

10 100 1000

With the ξ2 factor



Homework

1 Calculate the Z ′ partial widths Γ (Z ′→ qq) and Γ (Z ′→ χχ) for theZ ′-portal Lagrangians in Page 7(Results can be found in arXiv:1503.02931)

2 Draw Feynman diagrams for DM annihilation into τ+τ− in the MFDM andRSDM models described in Page 13

3 In the low velocity limit, derive the DM annihilation cross sections intoτ+τ−, ⟨σannv⟩, in Page 14 from the τ-portal Lagrangians in Page 13

4 Draw Feynman diagrams for stop decay processes t1→ tχ01 , bW χ0

1 , cχ01 ,

f f ′bχ01 , bχ±1 , and bτ+1ντ

5 Derive the neutralino mass matrix MN in Page 42 from the NMSSMsuperpotential and soft breaking terms


[.4em] lecture 3: dark matter searches at hadron...

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