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Dark matter and hidden U(1) X

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. Outline. Motivation Hidden U(1) X model and dark matter Constraints from EW precision Relic density and direct detection

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Dark matter and hidden U(1) X

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  1. 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

  2. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  3. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  4. Dark matter • 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

  5. Observational evidence

  6. Direct detection Direct detection experiments operate in deep underground laboratories to reduce the background from cosmic rays. HDMS CoGeNT TEXONO Detection techniques LUX KIMS

  7. CDMS: Directly detected? arXiv:0912.3592 • 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.”

  8. Why dark matter?

  9. Colliders Higgs, SUSY particles, Z’, etc It’s ON!

  10. Why U(1)X?

  11. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  12. Hidden U(1)X model • Hidden sector Lagrangian • Diagonalizing away the kinetic mixing term and mass mixing terms • Rotation angle • Redefined gauge boson masses

  13. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  14. ρ parameter • Mass of W • ρ parameter • Current bound on the ρ parameter (PDG)

  15. Unhatted expression • Defining and taking a leading order of • is expressed by unhatted parameters where

  16. Constraint from ρ

  17. Muon g-2 • Anomalous magnetic moment of the muon • Current limit arXiv:1001.5401 • Contribution from X exchange & modified Z couplings

  18. Muon g-2 limit

  19. 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%

  20. Constraint from APV

  21. Other EW observables hep-ph/0606183 Experimental measurements of these EW observables put limits on

  22. Bound on ε • Free parameters: ε, gX, mX, and mψ CDF limit on Z’

  23. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  24. Relic abundance • Relic density 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 .

  25. Direct detection

  26. Direct detection bound mψ= 500 GeV mψ= 100 GeV

  27. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  28. Collider limits • Limits on Z’ models • Decay widths

  29. Tevatron limit 1 CDF data on arXiv:0811.0053

  30. Tevatron limit 2

  31. LHC limit CDF limit 5σ limit for 10 fb-1

  32. Outline • Motivation • Hidden U(1)X model and dark matter • Constraints from EW precision • Relic density and direct detection • Collider limits • Conclusion

  33. Conclusion Debating • 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 mXand mψregion 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 GeVis still allowed for light DM (≤ 200 GeV). • LHC may discover Z’ in the near future. Especially, large mψ

  34. Thank you

  35. Backup

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

  37. Gauge interactions

  38. Simplified interactions • Gauge interactions with redefined couplings

  39. In the redefined physical basis (1st order of ω)

  40. Relic abundance 1 • Annihilation rate

  41. Direct detection

  42. Mψ=10 GeV

  43. Branching ratio to μ+μ- mψ= 100, 200, 500, 700 GeV

  44. σSI

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