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CP Violation in B s → J/ yj at the Tevatron

CP Violation in B s → J/ yj at the Tevatron. Karen Gibson. History. of Run II. In the beginning, measurement of DG s. ^. CDF measures DG s / G s = 0.65 +0.25 – 0.33 ps -1  D m s ~ 125 ps -1. Released in 2004, 270 pb -1 Phys. Rev. Lett . 94 , 101803 (2005).

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CP Violation in B s → J/ yj at the Tevatron

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  1. CP Violation in Bs → J/yjat the Tevatron Karen Gibson

  2. History

  3. of Run II In the beginning, measurement of DGs ^ CDF measures DGs/Gs= 0.65 +0.25 – 0.33 ps-1  Dms ~ 125 ps-1 Released in 2004, 270 pb-1 Phys. Rev. Lett. 94, 101803 (2005) Beauty 2009

  4. At that time, life was simpler… Didn’t know Dms no need for flavor tagging! Beauty 2009

  5. Definition of Transversity Angles J/yrest frame jrest frame VV final state defines 3D coordinate system

  6. Check angular fit with B0 J/yK*0 Beauty 2009

  7. D0 measurement soon follows… Measure DGs/Gs= 0.24 +0.28 – 0.38 ps-1 Released in 2005, 450 pb-1 Phys. Rev. Lett. 95, 171801 (2005) Beauty 2009

  8. D0 includes fit to CP phase bs Likelihood more complicated… Previously ignored these, 2bs ~ 0 in SM • d║ = arg(A║(0) A0*(0)) • d  = arg(A  (0) A0*(0)) Beauty 2009

  9. Released in Jul. 2006, 1.1 fb-1 Phys. Rev. Lett. 98, 121801 (2007) js = –0.79 ± 0.56 • Dotted line indicates 39% CL Note: js-2bs“experimentally” No flavor tagging  four-fold ambiguity in determination of phase js t (Bs0) = 1.52 ± 0.08 (stat) +0.01 -0.03 (syst) ps DG= 0.17 ± 0.09 (stat) ± 0.02 (syst) ps-1 Beauty 2009

  10. CDF finds that things are not so simple • Can reliably quote some point estimates with 2bs fixed to standard model prediction • Mean lifetime, DG, |A0(0)|2, |A║(0)|2, |A(0)|2 • When 2bs floats freely in fit, see significant biases and non-Gaussian errors in pseudo-experiments at low statistics

  11. Quote confidence regions, rather than point estimates, when bs floats freely For bs fixed to 0, find: t (Bs0) = 1.52 ± 0.04 (stat) ± 0.02(syst) ps DG= 0.076 +0.059-0.063 (stat) ± 0.006 (syst) ps-1 Released in Aug. 2007, 1.7 fb-1 Phys. Rev. Lett. 100, 121803 (2008) Beauty 2009

  12. Meanwhile, everything changes! CDF observes Bs mixing in 2006  measures Dms & validates calibration of SST Dms [ps-1] Dms = 17.77 ± 0.10 (stat) ± 0.07(sys) Beauty 2009

  13. Tevatron Flavor Tagging • b quarks generally produced in pairs at Tevatron • Tag either b quark which produces J/yj, or other b quark Same side Opposite side

  14. Tagged CP measurements now possible Time dependence on DG, Dms, 2bs CP asymmetry h = +1 Bs0,h = -1Bs0 Dependence on cos(Dmst) Beauty 2009

  15. For comparison, without flavor tagging… CP asymmetry h = +1 Bs0,h = -1Bs0 Beauty 2009

  16. Two exact symmetries are present in Bs0 J/yj untagged analysis: • 2bs – 2bs, d d + p • DG –DG, 2bs 2bs + p • Gives four equivalent solutions in bs and DG! • With flavor tagging, only one exact symmetry is present: • 2bs p – 2bs • DG –DG • d║ 2p – d║ • d p – d • Leads to two equivalent solutions in bs and DG! Beauty 2009

  17. Reduce number of solutions in DG-bs CDF observes 1.5s deviation from SM bs Released in Dec. 2007, 1.35 fb-1 Phys. Rev. Lett. 100, 161802 (2008) Beauty 2009

  18. Approximate symmetry also present… For low statistics, likelihood profile is not parabolic  cannot reliably separate the two minima! N(Bs) ~ 2000 Choose one solution by restricting d║ [0,p) Beauty 2009

  19. D0 also includes flavor tagging Constrain strong phases d║and d┴within p/5 of the values measured in B0 J/yK*0 N(Bs) ~ 2000 Released in Feb. 2008, 2.8 fb-1 Phys. Rev. Lett. 101, 241801 (2008) Beauty 2009

  20. Present

  21. Current CDF result Updated for ICHEP 08 http://www-cdf.fnal.gov/physics/new/bottom/080724.blessed-tagged_BsJPsiPhi_update_prelim/ Yield increased from N(Bs0) ~ 2000 (1.35 fb-1) to N(Bs0) ~ 3200 (2.8 fb-1) For bs fixed to 0 (& no flavor tagging), find: t (Bs0) = 1.53 ± 0.04 (stat) ± 0.01(syst) ps DG= 0.02± 0.05 (stat) ± 0.01 (syst) ps-1 Beauty 2009

  22. Observe deviation from SM bs of 1.8s Beauty 2009

  23. Transversity angles  not efficiency subtracted! Beauty 2009

  24. Present CDF result doesn’t fully utilize data • No particle ID in Neural Network selection • No SSKT after 1.3 fb-1 Beauty 2009

  25. Current D0 result D0 released constraint on strong phases d║, d┴, added systematic uncertainties to Dms Released in May 2009 http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B58/B58.pdf Beauty 2009

  26. D0 has also measured DG w/o tagging For bs fixed to 0, find: t (Bs0) = 1.48 ± 0.06 ps DG= 0.08 +0.07–0.08 ps-1 Released in Sept. 2008, 2.8 fb-1 Phys. Rev. Lett. 102, 032001 (2009) Beauty 2009

  27. Combination of CDF & D0 results Combined likelihood finds 2.1s deviation from SM Combination including other measurements of DG, e.g. asl, will be shown in Iain Bertram’s talk Updated for EPS 2009 http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B59/B59.pdf http://www-cdf.fnal.gov/physics/new/bottom/090721.blessed-betas_combination2.8/ Beauty 2009

  28. Deviation from Gaussian regime Beauty 2009

  29. Future

  30. Available data D0 has collected 6.1 fb-1 of data CDF has collected ~5.8 fb-1 Beauty 2009

  31. Tevatron plans for next results • Update measurement to full data available through summer shutdown • >5 fb-1 of data good for B physics per experiment • Use particle ID and full tagging (both OS and SS) (CDF) Beauty 2009

  32. Non-resonant K+K- under j mass Both CDF and D0 plan to make statement about S-wave contamination in m(K+K-) • LHCb just released study on the effect of neglecting the possible S-wave contribution • see talk by Olivier Leroy for details Released in Aug. 2009 arXiv:0908.3627 Beauty 2009

  33. Simultaneous minimization of CDF & D0 data • Idea is to combine CDF and D0 datasets before minimizing • Most powerful method of combining datasets • Could minimize data as usual or use Markov chain Monte Carlo to combine the datasets • Different interpretations (frequentist vs. Bayesian) • Have already set up technical framework to combine the two datasets • In the process of confirming individual expts’ results • Plan to use new combination method for 5 fb-1 results Beauty 2009

  34. Stay tuned to Tevatron for future results! Beauty 2009

  35. Back-up

  36. Tagged Likelihood Bs0: Time dependence in T, U, V Bs0: + - Beauty 2009

  37. Deviation from Gaussian regime Beauty 2009

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