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

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

4.  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

5. Observational evidence

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

7. 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

8. Why dark matter?

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

10. Why U(1) X ?

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

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

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 Contribution from X exchange & modified Z couplings Current limit arXiv:1001.5401

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

22. Bound on ε Free parameters: ε, g X, m X, and m ψ CDF limit on Z’

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

24. 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.

25. Direct detection

26. Direct detection bound m ψ = 100 GeV m ψ = 500 GeV

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

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 5 σ limit for 10 fb -1 CDF limit

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

33.  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

34. Thank you

35. Backup

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

37. Gauge interactions

38. Simplified interactions Gauge interactions with redefined couplings

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

40. Relic abundance 1 Annihilation rate

41. Direct detection

42. M ψ =10 GeV

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

44. σ SI