Dark matter and hidden U(1)X

(Work in progress, In collaboration with E.J. Chun & S. Scopel)

Park, Jong-Chul(KIAS)

August 10, 2010

Konkuk University

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

postulated by Fritz Zwicky in 1934 to explain missing mass of the Coma cluster a conjectured form of matter: undetectable by electromagnetic radiation presence can be inferred from gravitational effects accounts for 23% of the total mass-energy of the Universe

Dark matter

Observational evidence

Detection tech-niques

Direct detectionDirect detection experiments operate in deep underground laborato-ries to reduce the background from cosmic rays.

KIMS

HDMSCoGeNTTEXONO

LUX

CDMS: Directly detected?• CDMS II observed two candi-date events.• Background estimation due to surface leakage: 0.8±0.1 (stat)±0.2 (syst)• The probability that the 2 signals are just surface events is 23%.

“Our results can’t be inter-preted as significant evidence for WIMP interactions, but we

can’t reject either events as signal.”

arXiv:0912.3592

Why dark matter?

CollidersHiggs, SUSY particles, Z’, etc

It’s ON!

Why U(1)X?

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

Hidden U(1)X model• Hidden sector La-grangian

•Diagonalizing away the kinetic mixing term and mass mixing terms

• Rotation angle • Redefined gauge boson masses

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

ρ parameter• Mass of W

• ρ parameter

• Current bound on the ρ parameter (PDG)

•

Unhatted expression• Defining and taking a leading order of

• is expressed by unhatted parameters

where

Constraint from ρ

Muon g-2• Anomalous magnetic moment of the muon

• Contribution from X exchange & modified Z couplings

• Current limit arXiv:1001.5401

Muon g-2 limit

Atomic parity-violation• Weak charge: the strength of the vector part of the Z weak neutral current, i.e. the weak force• The weak charge governs the parity-violation effects in atomic physics.

• The deviation of experimental results from the SM prediction < 1%

Constraint from APV

Other EW observables

Experimental measurements of these EW observables put limits on

hep-ph/0606183

Bound on ε• Free parameters: ε, gX, mX, and mψ

CDF limit on Z’

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

Relic abundance• Relic den-sity

g*: # of relativistic degrees of freedom at

TF

TF : freeze-out temperature • Recent bound on DM relic density from WMAP7 arXiv:1001.4538 For each mψ , gX is determined as a function of mX .

Direct detection

Direct detection bound

mψ = 100 GeV

mψ = 500 GeV

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

Collider limits• Limits on Z’ models• Decay widths

Tevatron limit 1

CDF data on

arXiv:0811.0053

Tevatron limit 2

LHC limit

5σ limit for 10 fb-1

CDF limit

Motivation

Hidden U(1)X model and dark matter

• Constraints from EW precision

• Relic density and direct detection

• Collider limits

Conclusion

Outline

Is dark matter is directly detected?

A simple extension of the SM with a hidden U(1)X can provides a

viable DM candidate. Present EW precision tests are easily satisfied.

Small mX and mψ region is at the level of the sensitivity of direct

detection experiments at present and in the near future.

mX > 600 GeV is preferred by Tevatron limit.

However, mX < 600 GeV is still allowed for light DM (≤ 200

GeV).

LHC may discover Z’ in the near future. Especially, large mψ

ConclusionDebating

Thank you

Backup

Structure formation Cosmic microwave background radiation Baryon acoustic oscillations & Sky surveys Type Ia supernovae distance measurements Lyman alpha forest

Other evidence

Gauge interactions

Simplified interactions• Gauge interactions with redefined couplings

• In the redefined physical basis (1st or-der of ω)

Relic abundance 1• Annihilation rate

Direct detection

Mψ=10 GeV

Branching ratio to μ+μ-

mψ = 100, 200, 500, 700 GeV

σSI