Collider Constraints On Low Mass WIMP

Haipeng An, University of Maryland

Shanghai Jiao Tong UniversityIn collaboration with Xiangdong Ji, Lian-Tao Wang

中国科学院理论物理研究所冬季研讨会-- 暗物质与重子物质起源 2010.12.13-15

Outlines

Experiments;

Possible Interactions Between WIMP and SM particles;

Tevatron Constraints on the parameter space;

Tevatron Constraints on direct detection cross section;

Relic abundance;

Flavor changing neutral currents.

Direct Detection Experiments

CoGeNT

Observed excess could be explained by WIMP signal with mass in the range of 6~11 GeV. Cross section 10-41~10-40 cm2.

CRESST-II

CaWO4 32 events cannot be explained by known background. Can be explained by WIMP with mass around smaller than 15 GeV. And the cross section is about a few times 10-41 cm2 .

XENON100

Poisson smearing, null-result. New XENON100 result with a detecting power ten times larger will be published soon.

Direct Detection Experiments

15 GeV

5 GeV

Relic abundance

Thermal freezing-out

Thermal freezing-in (Multi-components)

SuperWIMP

Asymmetric dark matter

... ...

Using relic abundance as a lower bound

Tevatron Constraints

Leading jet ET > 80 GeV; pT of second jet < 30 GeV; Vetoing any third jet with ET > 20 GeV; Missing ET > 80 GeV. 1 fb-1 of data from Tevatron, 8449 events observed. SM background 8663±332;

Hard process is good enough.

Goodman, Ibe, Rajaraman, Shepherd, Tait, Yu (1005.1286, 1008.1783);

Bai, Fox, Harnik (1005.3797).

Aaltonen et al. [CDF Collaboration], PRL 101, 181602, 2008.Study the properties of large extra dimension

models

Contact Operator

In the work by Irvine group, effective four particle interaction is used to study the Tevatron constraint and LHC prediction.

However, in Tevatron the center-of-mass energy of the proton-anti-proton pair is 1.96 TeV, therefore if the mass of the intermediate particle is around a few hundred GeV, the interaction cannot be considered as a contact interaction.

Furthermore, if the result of CoGeNT is induced by elastic SI, MI collision between dark matter and nuclei, the effective coupling can be written as

Z-boson mediator

MDM << MZ.

Coupling between MZ and DM should be smaller than 0.02.

Relic abundance is too large.

Standard Model Higgs

If dark matter is a fermion, since the Yukawa couplings to light quarks are small. The relic abundance is too large.

However, if dark matter is a scalar, the relic abundance constraint can be avoided. (Xiao-gang’s talk)

Possible Interactions

SM Higgs + Scalar dark matter is still possible.

Dark matter: Complex Scalar (Φ), Dirac Fermion (χ).

Mediator: Scalar (H’), Vector (Z’).

T-channel annihilation, colored particle. (Will be study elsewhere).

More complicated cases …

Vector Mediator with Fermion WIMP

M*

gD=0.5, 1, 2, 3, 5

MZ’ = 5 GeV

Vector Mediator with Fermion WIMP

gD=0.5, 1, 2, 3, 5

430 GeV

450 GeV

480 GeV

500 GeV

Contact operator case

Tevatron constraint

Cannot saturate Tevatron bound in

perturbative region

Vector mediator fermion dark matter

Scalar mediator fermion dark matter

Vector mediator Scalar dark matter

Vector Mediator with Fermion WIMP

5 GeV

15 GeV

Dipole Interaction

Perturbatively

Non-perturbatively

Dipole Interaction

Direct detection cross section

Hadronic matrix elements

Electric Dipole coupling

Belanger, Boudjema, Pukhov, Semenov “MicrOMEGAs2.2” (0803.2360).

Fan, Reece, Wang (1008.1591).

Quark EDM

(QCD sum rules)

Pospelov, Ritz PRD 63, 073015

Power counting

Direct detection cross section

SI: Spin-independent ~ O(1)

SD: Spin-dependent ~ O(10-3~10-4)

MI: Momentum-indenpent ~ O(1)

MD: Momentum-dependent ~ O(10-6)

Magnetic Interaction

Tevatron Constraints on Direct Detection Cross Section

gD=1

gD=0.5

MZ’ < M* constraint on gZ’ does not depend on gD.

σ g∝ D- 2

Tevatron Constraints on Direct Detection Cross Section

MDM=5 GeV

MDM=15 GeV

Relic Abundance

Ωh2 ≈ 0.1pb / σ.

We choose gD=1 as a benchmark scenario to study the relic abundance.

During the thermal annihilation MDM/T ≈ 20, during this era, dark matter particles are non-relativistic.

For some operators the annihilation cross section are suppressed by v2.

JPC Group state of spin-1/2 fermion anti-fermion pair can only be 0-+ and 1--

Tevatron Constraints on Relic Abundance (MZ’>80 GeV)

5 GeV, 7 GeV, 10 GeV, 12 GeV, 15 GeV

Tevatron Constraints on Relic Abundance (MZ’>80 GeV)

NR suppression

Factor of 10

σ M∝ DM2

Dipole coupling (MZ’>80 GeV) Factor of 102

σ M∝ DM4

Scalar Mediator with Fermion DM

Vector Mediator and Scalar DM

Scalar Mediator with Scalar Dark Matter (MZ’>80 GeV)

Different Energy Scales

Collider:

In the case of Mmediator < M*, the mediator is produced on-shell and then decay to DM-anti-DM pair, the energy flowing into the DM anti-DM pair is just Mmediator.

Thermal annihilation:

The energy flowing into Z’ is 2MDM. Therefore, if the coupling is dimensional -1, like the dipole interaction case, the collider constraint on the thermal annihilation cross section is enhanced by a factor of (MDM/MZ’)2. Whereas, if the coupling is dimension 1, like the scalar mediator with scalar dark matter case, the constraint on thermal annihilation cross section is weakened by a factor of (MDM/MH’)2.

LEP II constraints on Z’ coupling to leptons If the MZ’ > 209 GeV, in the case of B-xL model, the constraint on x

is that MZ’/gZ’ > 6.2x TeV.

If MZ’ < 209 GeV, the coupling between Z’ and leptons should be smaller than 10-2.

In the case of gD=1, MZ’=80 GeV, MD=15 GeV, ge=gmu=gtau=0.01, the relic abundance is Ωh2 = 0.58, which is about 5 times larger than the observed one. Since Ωh2 ~ 0.1pb / σ, the contribution of the annihilation cross section from hadronic sector needs to be at least 5 time larger than from the lepton sector.

If gD gets larger, the constraint from thermal relic abundance is weakened.

Possible Interactions at gD=1, Mmediator>80 GeV

Other interactions are either suppressed by velocity or suppressed by MD / MZ’.

Except for the case of scalar mediator and scalar DM, the allowed cases are also stringently constrained.

Flavor Changing Neutral Current Quark rotation matrices can induce tree-level FCNC. In the case of

new scalar mediator.

If the vector mediator is non-universally coupled to quarks, it also suffers from tree-level FCNC constraints.

Summary

We consider elastic, single component, dark matter, specifically, complex scalar and Dirac fermion. The mediator we can considered are vector and real scalar.

In our study, the interaction is conducting by a propagating particle instead of a contact operator.

Collider constraints on the direct detection and relic abundance is studied especially for heavy mediator cases (M>80 GeV, gD=1).