1 / 43

L.Lista INFN Sezione di Napoli

L.Lista INFN Sezione di Napoli. Results of B A B AR experiment on CP violation and B physics. Outline. Experimental set-up CP asymmetries sin2 b sin2  eff B Mixing and lifetime Rare B decays Conclusions (Many topics will be skipped). (4S).

fraley
Download Presentation

L.Lista INFN Sezione di Napoli

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. L.ListaINFN Sezionedi Napoli Results of BABAR experiment on CP violation and B physics Luca Lista

  2. Outline • Experimental set-up • CP asymmetries • sin2b • sin2eff • B Mixing and lifetime • Rare B decays • Conclusions (Many topics will be skipped) (4S) Luca Lista

  3. center of mass energy  MU(4S) =10.58 GeV/c2 bg= 0.56 PEP-II at SLAC Low Energy Ring [e+, 3.1GeV] BaBar High Energy Ring [e-, 9.0GeV] The PEP-II B-Factory Luca Lista

  4. Integrated Luminosity 32 Million Y(4S) decays recorded • BaBar recorded: • 37.7fb-1 • 4.05 fb-1 off peak • Top luminosity: • 3.4x1033 cm-2s-1 • Design: • 3x1033 cm-2s-1 Luca Lista

  5. Electromagnetic Calorimeter 6580 CsI(Tl) crystals 1.5T solenoid e+ DIRC (PID) 144 quartz bars 11000 PMTs Drift Chamber 40 axial stereo layers e- Instrumented Flux Return 19 iron / 18-19 RPC layers Silicon Vertex Tracker 5 layers, 2-sided Si strips The BaBar detector Luca Lista

  6. A=(,) B=(1,0) C=(0,0) The Unitarity Triangle • Unitarity relations on matrix elements lead to a triangle in the complex plane • Quark mixing is described by the CKM matrix    1 Luca Lista

  7. B0 fCP B0 t d b B0 B0 W W t b d @Dt=0 B0 B0 F- F+ Dt(ps) CP violation at asymmetric B factory CP violation via mixing interference fCP eigenvalue  e-2ib For “golden” bccs modes: Luca Lista

  8. sin2b: Improvements w.r.t. run I • More data! • Added new modes • c1KS, J/K*0 • Improved reconstruction efficiency • Improved tracking • ~ +30% KS reconstruction eff. • Improved vertex resolution • New alignments • More elaborated vertex algorithm • Optimized KL selection taking into account the background CP asymmetry • Maximize (S+AB/ASB)2/(S+B), not S2/(S+B) Luca Lista

  9. All sin2b CP modes hCP = +1 IFR KL momentum not measured DE determined from B mass and beam energy constraints B0J/K0L N=129 (65% pur.) hCP = -1 B0J/K0S B0(2S)K0S B0cK0S N=724 EMC N=128 (56% pur.) Golden modes: ~30% higher efficiency than run 1: KS efficiency improved Luca Lista

  10. Fully reconstructed B flavor modes • Cabibbo favored decays: • B0D(*)-p+/r+/a1+ • B+ D(*)0 + , J/K+, (2S)K+ Luca Lista

  11. B01 partially reconstructed flavor tagged B02 fully reconstructed D*+  - or J/K0S e-e+ B1 = B0 B1 = B0 unmixedB0 B0 Dz Mixing and CP asymmetry of B0/B0 CP modes:FCP(Dt)  e-|Dt|/tB ( 1 hCPsin2b. sin Dmd Dt ) Flavour specific modes: Fflav(Dt)  e-|Dt|/tB ( 1 cosDmdDt ) mixedB0B0 or B0B0 Luca Lista

  12. Imperfect tagging and resolution D = 1-2w = dilution, w = wrong tag fraction R(Dt)= resolution function Imperfect tagging Imperfect resolution B0 B0 e-|Dt|/tB (1hCP sin2b  sin Dmd Dt) e-|Dt|/tB (1hCP Dsin2b sin Dmd Dt) e-|Dt|/tB (1hCP Dsin2b  sin Dmd Dt)  R(Dt) unmixed mixed e-|Dt|/tB (1cos DmdDt) e-|Dt|/tB (1 Dcos Dmd Dt) e-|Dt|/tB (1Dcos DmdDt)  R(Dt) Luca Lista

  13. Fitting Procedure • Unbinned maximum likelihood fit • Mistag and resolution: empirical distribution • fitted from data • fixed in the fit: md = 0.472 ps-1 (was extracted from the same fit in Run-I analysis) tB = 1.548 ps Separate for Run I & II Largest correlation With sin2b: 13% Luca Lista

  14. Flavor misid. measurement e w D=1-2w Q=e(1-w)2 s(sin2b) 1/(Q) Neural network mainly to recover unidentified leptons and use soft pions from D* Luca Lista

  15. sin2b result sin2b = 0.59 ± 0.14stat ± 0.05syst Luca Lista

  16. Comparison of different samples Submitted to Phys. Rev. Lett. On July 5 2001 Luca Lista

  17. 1s 2s Unitarity triangle sin2b = 0.59 ± 0.14stat ± 0.05syst Luca Lista

  18. Search for direct CP violation • Assuming more than one amplitude dominate the decay: || may be 1 • Only CP = -1 used • High purity, no assumption needed on CP of the background • No evidence found (none expected from SM) ||=0.93 ± 0.09 ± 0.03 Luca Lista

  19. Systematic errors • 0.03 from vertexing • 0.03 from tagging • 0.02 from background • Total 0.05 Luca Lista

  20. Dmdmeasurement preliminary Dmd= 0.519 ±0.020stat±0.016syst ps-1 Run I only Luca Lista

  21. Lifetime results B B0/B0 background Dt (ps) Dt (ps) t0 = 1.546  0.032(stat)  0.022(syst) ps t  = 1.673  0.032(stat)  0.022(syst) ps t0 /t = 1.082  0.026(stat)  0.011(syst) common resolution Luca Lista

  22. u u d d d d Charmless Hadronic Decays • Physics motivations • Significant penguin contribution • Direct CP violation studies • Measurement of  from time-dependent asymmetry + isospin analysis • Possible field for new physics… }p-(K-) Vud(s) d(s) W- Vub { b }p+ u B0 Cabibbo suppressed tree diagram }p-(K-) Vtd(s) W- d(s) Vtb }p+ { b u t B0 Penguin diagram Luca Lista

  23. Two body Branching fractions control sample: D*+D0, D0K-+ > 3 sigma Run I only p (GeV/c) Luca Lista

  24. CP violation in B0+-: sin2aeff • Neglecting penguin pollution: •  = f e-2i() = f e2i  C=0, S= sin2 • Considering penguin diagrams: • ||  1 • C  0, S= sin2eff = sin2  f (Penguin / Tree) • Extraction of sin2 requires the study of B000 and B000 • Fitted simultaneously with branching fractions • Dilutions and time resolutions taken from sin2b fit Run I + II expected ~0.3 preliminary ACP(K+p-) = -0.07  0.08  0.02 S = 0.03 +0.53-0.56  0.11 C  = 0.25 +0.45-0.47  0.14 Luca Lista

  25. Radiative Penguin: B  K* • Sensitive to top quark couplings • CKM matrix elements Vtd,Vts • Sensitive to New Physics • SUSY, Charged Higgs • No CP asymmetry in the Standard Model (< 1%) • Possible sources beyond SM Signal: B0  K*0, K*0  K+- Backgrounds: e+e-  qq  e+e-  qq  X 0 Luca Lista

  26. B0 K*0: yield and branching ratio • Nsignal = 139.2  13.1 events • Br(B0 K*0)= (43.9  4.1  2.7)  10-6 • Br(B Kl+l-) < 0.6  10-6 (90% C.L.) • Br(B K*l+l-) < 25.7  10-6 (90% C.L.) B0  K*0 K*0  K+p- Luca Lista

  27. BK, BK* • Penguin dominated Max Lik. Fit projections • B+K+=(7.7 +1.6-1.4  0.8)  10-6 • B+p+<1.4  10-6(90% C.L.) • B+K*+ =(9.7 +4.2-3.4  1.7)  10-6 • Possible measure of sin2b: • B0K*0 =(8.6 +2.8-2.4  1.1)  10-6 • B0 K0 =(8.1 +3.1-2.5  0.8)  10-6 Luca Lista

  28. Quasi 2-body and 3-body decays B+p+ = ( 6.6+2.1-1.80.7 )  10-6 B0K0 < 12 10-6 B+K+ = ( 70 85 )  10-6 B0K0 =( 42+13-114 )  10-6 B+K*+ = ( 22.1+11.1-9.2 3.3 )  10-6 B0K*0 = ( 19.8+6.5-5.61.7 )  10-6 B0K*0 p+ < 28  10-6 B+0K+ < 39  10-6 B+0p+ < 39  10-6 B+K+p+p- < 54  10-6 B+p+p+p- < 22  10-6 B0p =( 49  13 +6-5 )  10-6 B0a0(980)p Br(a0 p) = ( 6.7 +3.2-2.71.3 )  10-6 Potential for sin2a  First Observation  Luca Lista

  29. Search for direct CP violation Luca Lista

  30. B  D*D(*)K • Study of the bccs transition • Experimental inclusive estimate from from BDSX, (cc)X, CX, CX (ALEPH, CLEO) • Br(bccs) ~ 15.82.8 % • Theoretical calculation can’t determine this low value together with inclusive s.l. branching ratio (bcW) • Three-body B  DDK can contribute • Study of color suppressed modes (B+ D*+D*-K+) Color suppressed Color allowed Luca Lista

  31. B  D*D(*)K • Reconstructed decays: • D*+ D0p+ • D*0 D0p0 • D*0 D0g • D0 K-p+ • D0 K-p+p0 • D0 K-p+p-p+ • D+ K-p+p+ • Br(B0 D*+D0K+) = (0.280.070.05)10-2 • Br(B0 D*+D*0K+) = (0.680.170.17)10-2 • Br(B+ D*+D*-K+) = (0.340.160.11)10-2 • First observation of color suppressed mode other than B  (charmonium)X B0 (all modes) NS = 18021 B+ (all modes)NS = 11715 B+ D*+D*-K+ NS = 8.23.5 Luca Lista

  32. Conclusions • sin2 extracted from 37.7 millions of BB events sin2b= 0.59 ± 0.14stat ± 0.05syst • CP violation established at 4.1 level • First measurement of CP violation in B0 • High precision measurements of mixing parameter and lifetimes • High precision measurements of B decays branching fractions • Many newly observed decays • Most of the results are still statistically limited Luca Lista

  33. Backup slides Luca Lista

  34. J/ K* angular analysis J/ rest frame K* decay plane Channels withoutp0 f (costr, cosK*, tr) = f1|A0|2 + f2|A|||2 + f3|A|2 +f4Im(A||* A) + f5Re (A0* A||) + f6Im (A0* A) Channels withp0 • L=0,1,2 waves • Both CP even and odd amplitudes are present • Measurement of sin2b is possible from angular analysis Time dependent CP asymmetry dilution factor: D =1 – 2|A|2 = 0.680.10 Luca Lista

  35. B0 D*+D*- • Cabibbo suppressed decay • A measurement in bccd of CP violating time-dependent asymmetry can be performed from angular analysis • Possible penguin contamination • Measurement of sin2b independent from B0J/K0S • Significant deviations from B0J/K0S measurement of sin2b may be indication of new physics Tree diagram Penguin contribution • Branching ration measurement of B  D(*)+D(*)-: Luca Lista

  36. Signal box (38 events) Background sample (6.240.49 expected in signal box) B0 D*+D*- Br(B0D*+D*-) = (8.0  1.6  1.2)10-4 Luca Lista

  37. J/ +- J/ e+e- p*J/ < 2 GeV/c Inclusive Charmonium decays c J/, (2S), c b c • Inclusive J/branching ratio: Br(BJ/X) = (1.0440.013 0.028)10-2 Br(BJ/X dir.) = (0.7890.010 0.034)10-2 • Inclusive (2S)branching ratio: Br(B (2S) X) =(0.2750.020 0.029) 10-2 • (2S)l+l-branching ratio: (2S)  e+e- (7.8  0.9  0.8)10-3 (2S)  +- (6.7 0.8  0.7)10-3 • Inclusive cbranching ratios: Br(B c1 X) = ( 0.378  0.034  0.026 )  10-2 Br(B c1 X dir.)= ( 0.353  0.034  0.024 )  10-2 Br(B c2 X) < 0.2110-2 @ 90% C.L.= ( 0.137  0.058  0.012 )  10-2 W- B0, B- s, d X d, u Br((2S)  J/p+p-)assumed from PDG Luca Lista

  38. Exclusive B decays • Main motivation: • Channels are used for CP violation measurements • Kinematics selection: • Energy substituted mass • Independent on particle mass hypotheses • Energy difference in the center of mass B0J/ 0 First observation: B0c1 K*0 Luca Lista

  39. J/ production in continuum • First observation of J/ production in continuum • (4S) events with p*J/>2 GeV/c • Off-resonance events Angular distribution1+A cos2q* • A (all E*) = 0.250.19 • A (p*>3.5 GeV) l= 0.620.39 • Color singles prediction:   0.8 pb A  –0.8, • NRQCD (c.o.) prediction:   2.8 pb 0.6<A<1.0 Luca Lista

  40. Branching ratios results RUN 1: 22.7 MBB Luca Lista

  41. l+or l- e-e+ l+or l- N+–, –+ – N++, –– Asymmetry A(Dz)= N+ –, –+ + N++, –– Dz Dmdmeasurement: the di-lepton analysis Dmd= 0.499 ± 0.010 ± 0.012 ps-1 Luca Lista

  42. Semileptonic B decays • Determine the sign of the B from a sample of ~14000 fully reconstructed B B0D(*)-+, D(*)-+, D(*)-a1+, J/K*0 B- D(*)0+, J/K+, (2S)K+ • Lepton identified in the decay of the other B B+ B0 Mixing corrected Luca Lista

  43. bs, B0 mES for 0.6 <mhad < 2.0 GeV • Semi-exclusive study • Sum of exclusive modesK+np (n=1,2,3) Branching ratio measurementcoming soon… B0   • Theoretical exp.: ~ 10-8 • Br(B0) < 1.7 x 10-6 90% C.L. • PDG: Br(B0 ) < 3.9 x 10-5 90% C.L. (L3) Luca Lista

More Related