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
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