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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
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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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
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Observational evidence
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Detection techniques Direct detection Direct detection experiments operate in deep underground laboratories to reduce the background from cosmic rays. KIMS HDMS CoGeNT TEXONO LUX
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CDMS: Directly detected? CDMS II observed two candidate 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 interpreted as significant evidence for WIMP interactions, but we can’t reject either events as signal.” arXiv:0912.3592
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Why dark matter?
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Colliders Higgs, SUSY particles, Z’, etc It’s ON!
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Why U(1) X ?
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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Hidden U(1) X model Hidden sector Lagrangian Diagonalizing away the kinetic mixing term and mass mixing terms Rotation angle Redefined gauge boson masses
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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ρ parameter Mass of W ρ parameter Current bound on the ρ parameter (PDG)
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Unhatted expression Defining and taking a leading order of is expressed by unhatted parameters where
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Constraint from ρ
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Muon g-2 Anomalous magnetic moment of the muon Contribution from X exchange & modified Z couplings Current limit arXiv:1001.5401
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Muon g-2 limit
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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%
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Constraint from APV
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Other EW observables Experimental measurements of these EW observables put limits on hep-ph/0606183
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Bound on ε Free parameters: ε, g X, m X, and m ψ CDF limit on Z’
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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Relic abundance Relic density g * : # of relativistic degrees of freedom at T F T F : freeze-out temperature Recent bound on DM relic density from WMAP7 arXiv:1001.4538 For each m ψ, g X is determined as a function of m X.
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Direct detection
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Direct detection bound m ψ = 100 GeV m ψ = 500 GeV
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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Collider limits Limits on Z’ models Decay widths
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Tevatron limit 1 CDF data on arXiv:0811.0053
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Tevatron limit 2
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LHC limit 5 σ limit for 10 fb -1 CDF limit
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Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection Collider limits Conclusion Outline
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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 m X and m ψ region is at the level of the sensitivity of direct detection experiments at present and in the near future. m X > 600 GeV is preferred by Tevatron limit. However, m X < 600 GeV is still allowed for light DM (≤ 200 GeV). LHC may discover Z’ in the near future. Especially, large m ψ Conclusion Debating
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Thank you
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Backup
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Structure formation Cosmic microwave background radiation Baryon acoustic oscillations & Sky surveys Type Ia supernovae distance measurements Lyman alpha forest Other evidence
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Gauge interactions
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Simplified interactions Gauge interactions with redefined couplings
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In the redefined physical basis (1 st order of ω )
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Relic abundance 1 Annihilation rate
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Direct detection
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M ψ =10 GeV
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Branching ratio to μ + μ - m ψ = 100, 200, 500, 700 GeV
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σ SI
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