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BaBar: Risultati recenti e prospettive

BaBar: Risultati recenti e prospettive. Fernando Ferroni Universita’ di Roma “La Sapienza” & I.N.F.N. Roma1. BABAR Collaboration. China [ 1/5 ] Inst. of High Energy Physics, Beijing Germany [ 3/23 ] Ruhr U Bochum TU Dresden U Rostock France [ 5/51 ] LAPP, Annecy LAL Orsay

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BaBar: Risultati recenti e prospettive

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  1. BaBar: Risultati recenti e prospettive Fernando Ferroni Universita’ di Roma “La Sapienza” & I.N.F.N. Roma1

  2. BABAR Collaboration China [1/5] Inst. of High Energy Physics, Beijing Germany[3/23] Ruhr U Bochum TU Dresden U Rostock France [5/51] LAPP, Annecy LAL Orsay LPNHE des Universités Paris 6/7 Ecole Polytechnique CEA, DAPNIA, CE-Saclay United Kingdom [10/71] U of Birmingham U of Bristol Brunel University U of Edinburgh U of Liverpool Imperial College Queen Mary & Westfield College Royal Holloway, University of London U of Manchester Rutherford Appleton Laboratory Italy [12/89] INFN Bari INFN Ferrara INFN Frascati INFN Genova INFN Milano INFN Napoli USA [36/253] Caltech, Pasadena UC, Irvine UC, Los Angeles UC, San Diego UC, Santa Barbara UC, Santa Cruz U of Cincinnati U of Colorado Colorado State Elon College Florida A&M U of Iowa Iowa State U LBNL LLNL U of Louisville U of Maryland U of Massachusets MIT U of Mississippi Mount Holyoke College Northern Kentucky U U of Notre Dame ORNL/Y-12 U of Oregon U of Pennsylvania Prairie View A&M Princeton SLAC U of South Carolina Stanford U U of Tennessee U of Texas at Dallas Vanderbilt U of Wisconsin Yale U INFN Padova INFN Pavia INFN Pisa INFN Roma INFN Torino INFN Trieste Canada [4/15] U of British Columbia McGill U U de Montréal U of Victoria Norway [1/2] U of Bergen Russia [1/7] Budker Inst., Novosibirsk

  3. PEPII

  4. BaBar SVT: z resolution ~70 microns Tracking: (pT)/pT = 0.13%  pT 0.45% DIRC: K- separation > 3.4 for P<3.5GeV EMC: E/E = 1.33%E-1/4  2.1%

  5. Outline PEPII & BaBar Physics Motivation: CP in B Results: Mixing & Lifetimes sin 2b Rare decays Perspectives

  6. Particle physics in new millennium Origin of masses Remote energy scale (Gravity) CP Violation and our universe

  7. Why CP violation ? Needed for matter-antimatter asymmetry Standard Model CP-Violation (CKM) thought to be insufficient to explain universe asymmetry 37 years of intense experimental and theoretical effort of background

  8. CP Violation in SM SM with three generation accommodates CP violation through phase in CKM matrix SM predicts a variety of CP violating asymmetries in the B-system,some of which can be cleanly interpreted in terms of CKM matrix elements

  9. The Triangle CP Bd D*p , Kp

  10. The Unitarity Triangle The sides are determined by measurements of the magnitudes of CKM elements CP asymmetries to fCP measures angles of triangle, in some cases with little or no theoretical ambiguities Goal of the B-physics program is to overconstrain triangle, critically test CKM structure of SM

  11. CP measurement • Reconstruct a CP eigenstate • Flavour tag with other B • Measure Dz ---> Dt = tCP - ttag • Fit time evolution

  12. gbct/2 bg=0.56 gbct Y(4S) 250 m B decay topology Reconstruction of the CP eigenstate Tag of the other B B0 B0 Measurement of Dz Lifetime, Mixing, CP

  13. Smearing of an asimmetry

  14. PEPII-BaBar Operations Design: 3.0 nb-1/s 135 pb-1/d ~0.80 fb-1/w ~ 3.3 fb-1/m Achieved:3.28 184 1.03 3.8 • Data from 1999-2000 run • 20.7 fb-1 on-resonance • N((4S)) = 22.74 ±0.36 million • 2.6fb-1 off-resonance

  15. PEPII-BaBar Operations

  16. Interaction region Permanent magnets inside the support tube

  17. J/Y Ks Event at BaBar B0J/Y Ks J/Y->m+m- Ks -> p+p-

  18. e+ e- DIRC: Detection of Internally Reflected Cherenkov light New design for a Cherenkov detector 144 quartz bars (1.7 cm thick) 10752 PMT in 6 m3 of purified water Total space: 8 cm (0.14 X0)

  19. K/p separation Pion-Kaon separation at high momenta

  20. Mixing and sin2b Common wrong tag fractions and resolution function parameters can be determined by a large Bflav sample

  21. Bflav sample B0 D(*) -p+, D(*) -r+, D(*) -a1+, J/YK*0 B- D(*)0 p- , J/YK-, Y(2S)K- DE=E*B - s /2 s~15 MeV mES= (s/4 - p*B2) s~3MeV

  22. B reconstruction • Y(4S)->BB energy difference energy substituted (constrained) mass DE sideband DE mES sideband signal mES one more pion...

  23. Bflav sample 6368 evts Purity ~ 84% 7645 evts Purity ~ 86%

  24. Run I Data Set 23M BBpairs recorded 3 fb-1 of continuum

  25. CP sample (Ks modes) J/ YKs (+-)259 (purity 98%) J/Y l l J/ YKs (00)50 (84%) Y(2s)Ks (+-)55 (97%) Y(2S)  l l  J/Ypp

  26. Final CP sample of K0s modes

  27. CP sample (KL modes) Neutral clusters not consistent with noise, g or p0 are considered as KL candidates B mass constraint is imposed 92 signal Purity =40% 108 signal Purity =51% Reconstructed with EMC Reconstructed with IFR

  28. Tagging

  29. Vertexing Dt=Dz/< bg c> Use per event error and parametrize the resolution function with scaling factors

  30. Lifetimes PDG 1.55±0.03 1.65±0.03 1.06±0.03 B0 = 1.546  0.032  0.022 ps B+ = 1.673  0.032  0.022 ps B+/ B0 = 1.082  0.026  0.011

  31. Mixing adronico/leptonico

  32. Mixing : compilation

  33. Fitting procedure Mixing and sin2b measurements are done with the same strategy: do a global fit to all the events that can carry information Mixing : tagged flavour eigenstates sin2b : tagged flavour and CP eigenstates Extract as many parameters as possible from data Biggest correlation with sin2b 7.6%

  34. Log Likelihood vs sin 2  Total KS KL  sin 2  = 0.34  0.20(stat)  0.05(sys)

  35. Systematics

  36. Asymmetries sin2b=0.25  0.22 (stat) J/Y KS sin2b=0.87  0.51 (stat) J/Y KL

  37. Asymmetries Total CP tagged sample : 529 events 164 of background mainly in J/Y KL

  38. sin2b by decay mode

  39. sin2b by tagging category (Ks only)

  40. Compilation of all known results

  41. Comparison to predictions of non-CP sin 2b |eK | |Vub/Vcb|, DMd,DMs

  42. New fuel for sin2b (B  D*+D*-) The Standard Model predicts time-dependent CP-violating asymmetries in the decays B0 D(*)+D(*)- proportional to sin2b • D*+ Reconstruction • D*+ D0p+, D+p0 D0 K-p+, K-p+p0, K-p+p-p+, KSp+p- D+  K-p+p+, KSp+, K-K+p+

  43. New fuel for sin2b Beware of this one (non flying birds !)

  44. B  D*+D*-, Signal • Nsignal = 31.8 Events • NBkg = 6.2 Events • Estimated from sideband in DE and MES Br(B0D*+D*-) = (8.0 ± 1.6 (stat) ± 1.2 (syst))  10-4 (But angular analysis to do CP)

  45. Charmless two-body B decays Direct CP search Time-dependent CP asymmetry p+p-  sin(2a),fK0 sin(2b) Theoretical model validation u Vud,s p+, K+ d,s W Vub b u p- B0 d d Cabibbo-suppressed tree diagrams Vtb Vtd,s d,s b W p+, K+ u B0 t u p- d d penguin diagrams

  46. Charmless decays p+p-, K+p-, K+K- (h+h-) p0 p+, p0 K+ (p0 h+) K0 p+, K0 K+ (K0 h+) K0p0 fK*+ fK+,fp+ fK0 K0 as KS to p+p- fK+K- K*+ K+p0,KS p+ Fully reconstructed decays Efficiency (with daughter BF) K0p0,h+p0,h+K0,h+h: 10-45% fK*+,fK0,fK+ :3-20%

  47. Composite particles < E > ~ 3 GeV s=8.5 MeV s=4.3 MeV p0 mass f mass KS mass

  48. Background suppression p0 Jet-like topology background Background dominated by continuum qqbar production (u,d,s,c) cos qS signal cos(qS) cosine of angle between sphericity axes of B and rest of the event

  49. Background suppression Fisher discriminant Linear combination of event-shape variables (cones) h+h-DE sideband(dots) continuum h+h- MC(his) (dots) B- D0p- (his)h+h- MC background signal

  50. Likelihood analysis • Use an extendedglobal likelihood fit to extract • different signal yields (NS) in each topology mES, DE, Fisher(cosqTh), (f mass), qC • Independent control sample to study Probability • Density Function for both BKG and SIG h+h- DE sideband B- Dop- ARGUS function Gaussian s 2.6 MeV

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