1 / 41

CP Violation in B 0 s mesons Results from flavor tagged analyses of B 0 s  J/ y f Joe Boudreau

CP Violation in B 0 s mesons Results from flavor tagged analyses of B 0 s  J/ y f Joe Boudreau University of Pittsburgh For the CDF and D0 Collaborations. ≠. V ub * V ud. V tb * V td. b. V cb * V cd. A very brief abstract of this talk first. The following topics will be developed:.

beate
Download Presentation

CP Violation in B 0 s mesons Results from flavor tagged analyses of B 0 s  J/ y f Joe Boudreau

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CP Violation in B0s mesons Results from flavor tagged analyses of B0s J/y f Joe Boudreau University of Pittsburgh For the CDF and D0 Collaborations ≠

  2. Vub*Vud Vtb*Vtd b Vcb*Vcd A very brief abstract of this talk first. The following topics will be developed: Vcb*Vcs CDF and D0 use B0s J/y f to measure CKM phases. We determine from this decay the quantity bs. This is in exact analogy to B factory measurement of the b, an angle of the unitarity triangle. The standard model makes very precise predictions for both angles. But other new particles & processes, lurking potentially in quantum mechanical loops such as box diagrams and penguin diagrams can change the prediction. Vub*Vus bs Vtb*Vts Joe Boudreau HQL Melbourne June 5-9 2008

  3. Example of new physics: a fourth generation quark that contributes to the mixing phase Wei-Shu Hou, arXiv:hep-ph/0803.1234 Would have other measureable consequences: e.g. an impact on direct CP violation in B0K+p- and B+K+p0 Joe Boudreau HQL Melbourne June 5-9 2008

  4. B0s→J/yf * B0s→J/yfis two particles decaying to three final states.. Two particles: Three final states: J/yf in an S wave CP Even J/yf in a D wave CP Even J/yf in a P wave CP Odd Light, CP-even, shortlived in SM Heavy, CP-odd, longlived in SM Manifestations of CP violation in B0sJ/y f A supposedly CP even initial state decays to a supposedly CP odd final state…. like the neutral kaons Measurement needs DG≠0 but not flavor tagging. The polarization of the two vector mesons in the decay evolves with a frequency of Dms Measurement needs flavor tagging, resolution, and knowledge of Dms Joe Boudreau HQL Melbourne June 5-9 2008

  5. Time dependence of the angular distributions: use a basis of linear polarization states of the two vector mesons { S, P, D}  { P, P||, P0 } CP odd states decay to P CP even states decay to P|| ,P0 If [H,CP] ≠ 0 Then • The polarization correlation • depends on decay time. • Angular distribution of decay • products of the J/y and the f analyze the rapidly oscillating • correlation. Dms~ 17.77 ps-1. A. S. Dighe, I. Dunietz, H. J. Lipkin, and J. L. Rosner, Phys. Lett. B 369, 144 (1996), 184 hep-ph/9511363. Joe Boudreau HQL Melbourne June 5-9 2008

  6. The measurement is an analysis of time-dependent angular distributions … formula suggests an analysis of an oscillating polarization. This innocent expression hides a lot of richness: * CP Asymmetries through flavor tagging. * sensitivity to CP without flavor tagging. * sensitivity to both sin(2bs) and cos(2bs) simultaneously. * Width difference * Mixing Asymmetries Joe Boudreau HQL Melbourne June 5-9 2008

  7. CP Violation in the interference of mixing and decay for the B0s system Take: q/p from the mixing of B0s - B0s Take: Ā/A from the decay into { P, P||, P0 } Form: the (phase) convention-independent and observable quantity: This number is real and unimodular if [H,CP]=0 Joe Boudreau HQL Melbourne June 5-9 2008

  8. Very famous measurement of CP Asymmetries in B0J/y K0s Vub*Vud Vtb*Vtd b Vcb*Vcd |B0> | J/y K0s > |B0> BABAR, BELLE have used this decay to measure precisely the value of sin(2b) an angle of the bd unitarity triangle. There was a fourfold ambiguity http://ckmfitter.in2p3.fr/ Joe Boudreau HQL Melbourne June 5-9 2008

  9. Babar, Belle resolve an ambiguity in b by analyzing the decay B0J/y K0* which is BV V and measures sin(2b) and cos(2b) This involves angular analysis as described previously Phys.Rev. D71 (2005) 032005 J/y K0* Phys.Rev.Lett. 95 (2005) 091601 | P|| > |B0> | P0 > |m+m-K0sp0> |B0> |B0> | P > Joe Boudreau HQL Melbourne June 5-9 2008

  10. Today I will tell you about an analysis of an almost exact analogy, |Bs0>  J/y f (but I think that in the B0s system the phenomenology is even richer! Because of the width difference! ) J/y f | P|| > |Bs0> | P0 > |m+m-K+K-> |Bs0> |Bs0> | P > Joe Boudreau HQL Melbourne June 5-9 2008

  11. The decay B0sJ/yf obtains from the decay B0J/y K0* by the replacement of a d antiquark by an s antiquark b d s W W B0→J/y K0* c W d c b s s W W Bs0→J/yf c W s c We are measuring then not the (bd) unitarity triangle but the (bs) unitarity triangle: Vub*Vud Vtb*Vtd Vcb*Vcs b Vub*Vus bs Vtb*Vts Vcb*Vcd Joe Boudreau HQL Melbourne June 5-9 2008

  12. The analysis of B0s→J/y f can extract these physics parameters: The measurement of bs and DG are correlated; from theory one has the relation DG = 2|G12|cos(2bs) with |G12| = 0.048 ± 0.018 and A. Lenz and U. Nierste, J. High Energy Phys. 0706, 072 (2007). The exact symmetry.. … is an experimental headache. Joe Boudreau HQL Melbourne June 5-9 2008

  13. 2019 ± 73 events 1967 ± 65 events Joe Boudreau HQL Melbourne June 5-9 2008

  14. SST +OST: eD2 = 4.68 ± 0.54% SST: eD2 3.6% OST: eD2 1.2% Flavor Tagging Each tag decision comes with an error estimate validated: 2. In the B0s mixing (SST) 1. Using B± (OST) Joe Boudreau HQL Melbourne June 5-9 2008

  15. CDF Untagged Analysis (1.7 fb-1) Phys. Rev. Lett. 100, 121803 (2008) Feldman-Cousins confidence region in the space of the parameters 2bs and DG HQET: ct(B0s)= (1.00±0.01) ct(B0) PDG: ct(B0) = 459 ±0.027 mm Joe Boudreau HQL Melbourne June 5-9 2008

  16. Tagged analysis: likelihood contour in the space of the parameters bs and DG Phys. Rev. Lett. 100, 161802 (2008) One ambiguity is gone, now this one remains Joe Boudreau HQL Melbourne June 5-9 2008

  17. A frequentist confidence region in the bs-DG including systematic errors is the main result. This interval is based on p-values obtained from Monte Carlo and represents regions that contain the true value of the parameters 68% (95%) of the time. arXiv:0712.2397v1 The standard model agrees with the data at the 15% CL Joe Boudreau HQL Melbourne June 5-9 2008

  18. There is no way that this measurement can remove the remaining ambiguity alone. External constraints on the phases, from B factories, can do, but they may not be applicable: Constrain strong phases d|| and d to BaBar Values (for B0J/y K*) Constrain ts to PDG Value for B0 Apply both constraints. using values reported in: B. Aubert et al. (BABAR Collaboration), Phys. Rev. D 71, 032005 (2005). Joe Boudreau HQL Melbourne June 5-9 2008

  19. The D0 Result is a confidence interval using an external constraint: Strong phases varying around the world average values ( for B0J/y K*); Gaussian constraint with s=p/5 is applied. D0 Result fs=-2bs arXiv:0802.2255 Prev result: PRD 76, 057101 (2007) Contours are 68% CL and 90% CL Joe Boudreau HQL Melbourne June 5-9 2008

  20. 1 D Contours & Confidence Intervals Likelihood contours for just DG and for just fs=-2bs fs=-0.57 +0.24 – 0.30 DG=0.19 ±0.07 ps-1 (1) 2bs [0.32, 2.82] at the 68% CL. Assuming |G12| = 0.048 ± 0.018 and the relation DG = 2|G12|cos(2bs): (2) 2bs [0.24,1.36] U [1.78, 2.90] at the 68% CL. Constrain d|| and d to the results from B0 J/y K*0 decays & ts = td (3) 2bs [0.40, 1.20] at 68% CL FC Confidence Intervals: Joe Boudreau HQL Melbourne June 5-9 2008

  21. Outlook • Note fs = -2bs • Fluctuation or something more, it does go in the same direction. • CDF estimates a p-value of 15% for the standard model, using Monte Carlo • D0 estimates a p-value of 6.6% using Monte Carlo Joe Boudreau HQL Melbourne June 5-9 2008

  22. UTFit group has made an “external” combination. arXiv:hep-ph/0803.0659 • “re-introduces” the ambiguity into the D0 result. • does so by symmetrizing. • cannot fully undo the strong phase constraint. • I am showing you this conclusion, but not endorsing it • very enthusiastically. D0 is now producing a result without the strong phase constraint. HFAG is preparing to combine the two unconstrained results Joe Boudreau HQL Melbourne June 5-9 2008

  23. Further comments: • We have assumed so far that: • and thus |l| = 1 .. To a very good approximation. In higher order however |q| ≠ |p| and |l|≠1 (at the level of 1-|l| < 2.5 x 10-3) Semileptonic asymmetry: HQET: G12/Ms12 =(49.7 ±9.4) ±10−4 • AsSL= 0.020 ± 0.028 (CDF) http://www-cdf.fnal.gov/physics/new/bottom/070816.blessed-acp-bsemil/ • AsSL= 0.0001 ± 0.0090 (stat) (D0) Phys. Rev. D 76, 057101 (2007) Joe Boudreau HQL Melbourne June 5-9 2008

  24. Conclusion • Towards the end of a 20-year program in proton-antiproton physics: • some terribly interesting times for the physics of the b-quark. • An anomaly from the B factories • Are quantum loop corrections to the bs transitions to blame? • If so, precision measurements of the CP asymmetries in the B0s system are • a clean way to sort it out. • D0 and CDF have just demonstrated the feasibility of doing those • measurements; more work needed now to • understand the true significance. • Higher precision, higher statistics • measurements could give us a • even stronger hint as the LHC • begins taking data. Lin, S.-W. et al. Nature 452,332–335 (2008). Joe Boudreau HQL Melbourne June 5-9 2008

  25. FIN Joe Boudreau HQL Melbourne June 5-9 2008

  26. Free Bonus Slides Joe Boudreau HQL Melbourne June 5-9 2008

  27. where i = 0, para, perp and An analysis of the decay can be done with either a mix of B and B mesons (untagged) or with a partially separated sample (flavor tagged). Latter is more difficult and more powerful. B B These expressions are: * used directly to generate simulated events. * expanded, smeared, and used in a Likelihood function. * summed over B and B (untagged analysis only) Joe Boudreau HQL Melbourne June 5-9 2008

  28. For reference: expanded, smeared , normalized rates: obtain the overall time and angular dependence: Joe Boudreau HQL Melbourne June 5-9 2008

  29. Explicit time dependence is here: … then, replace exp, sin*exp, cos*exp with smeared functions. Joe Boudreau HQL Melbourne June 5-9 2008

  30. Curiosity #1: cos(2bs) is easier to measure than sin(2bs). It can be done in the untagged analysis for which the PDF contains time dependent terms: Physically this is accessible because one particular lifetime state (long or short) decays to the “wrong” angular distributions. Needs DG≠0; no equivalent in B0J/y K0*. Some fine print: in the interference term, in an untagged analysis, there is a term including sin(2bs); however this term does not determine the sign of sin(2bs) so it does not solve any ambiguity. Joe Boudreau HQL Melbourne June 5-9 2008

  31. Curiosity #2: Sensitivity to Dms (tagged analysis only; even in the absence of CP) How much sensitivity? Well, we did not exploit it yet but it could be important news at the LHC! Joe Boudreau HQL Melbourne June 5-9 2008

  32. = Vub*Vud = O(l3) Vtb*Vtd= O(l3) With l = 0.2272± 0.0010 A = 0.818 (+0.007 -0.017) r = 0.221 (+0.064-0.028) h = 0.340 (+0.017-0.045) One easily obtains a prediction for bs : 2bs = 0.037±0.002 b Vcb*Vcd = O(l3) Vcb*Vcs= O(l2) b’ Vub*Vus= O(l4) Vtb*Vts= O(l2) Joe Boudreau HQL Melbourne June 5-9 2008

  33. Elsewhere there is another anomaly that may also have to do with bs * Direct CP in B+K+p0 and B0 K+p- are generated by the b s transition. These should have the same magnitude. * But Belle measures (4.4 s) * Including BaBar measurements: > 5s Lin, S.-W. et al. (The Belle collaboration) Nature 452,332–335 (2008). • The electroweak penguin can break the isospin symmetry • But then extra sources of CP violating phase would be required in the penguin Joe Boudreau HQL Melbourne June 5-9 2008

  34. In general the most important components of a general purpose • detector system, for B physics, is: • tracking. • muon [+electron] id • triggering: B hadrons comprise is O(10-3) of all events. • Charmless decay modes have branching fractions O(10-6) Joe Boudreau HQL Melbourne June 5-9 2008

  35. The D0 Silicon tracker….. • surrounded by a fibre tracker at a distance 19.5 cm < r <51.5 cm • now augmented by a high-precision inner layer (“Layer 0”) • 71 (81) mm strip pitch • factor two improvement in impact parameter resolution Joe Boudreau HQL Melbourne June 5-9 2008

  36. CDF Detector showing as seen by the B physics group. Muon chambers for triggering on the J/y→m+m- and m Identification. Strip chambers, calorimeter for electron ID Central outer tracker dE/dX and TOF system for particle ID r < 132 cm B = 1.4 T for momentum resolution. Joe Boudreau HQL Melbourne June 5-9 2008

  37. L00: 1.6 cm from the beam. 50 mm strip pitch Low mass, low M-S. Uses precise impact parameter information at trigger level 2, to collect hadronic decays of b-hadrons. Joe Boudreau HQL Melbourne June 5-9 2008

  38. The extent to which these features show up depends upon numerical values of the constants governing mixing, decay, direct CP violation and CP asymmetries: • The B0s system is characterized by the following standard model expectations: • Very fast oscillation frequency. • Small but observable (~10%) lifetime difference. • Very small CP violation in the standard model. Joe Boudreau HQL Melbourne June 5-9 2008

  39. Contrast this phenomenology with that of B0 mesons. Slow oscillation Dmd = 0.507 ±0.005 ps-1  Oscillation length cT = 3.7 mm Large Standard Model CP violation Fast oscillation Dms ~ 18 ps-1 Oscillation length cT = 110 mm Zero Standard Model CP violation (almost) http://utfit.roma1.infn.it/

  40. Tagger performance in J/yf decays: Dilution: (27±4)% Efficiency: (50±1)% Dilution: (11±2)% Efficiency: (96±1)% Joe Boudreau HQL Melbourne June 5-9 2008

  41. The quality of the Prediction of dilution Can be checked against the data: We reconstruct a sample Of B± decays in which one knows the sign of the B meson. We then “predict” the sign of the meson and plot the predicted dilution vs the actual dilution. Separately for B+ and B- Scale (from lepton SVT this sample; take the difference B+/B- as an uncertainty).

More Related