1. Recent Results from B A B AR P.-Fabrizio Salvatore Royal Holloway College, University of London Measurement of sin2  Measurement of sin2  Many thanks to Dr. T.McMahon (RHUL) University of Glasgow, 23 January 2003

2. November 26, 2002Fabrizio Salvatore, Royal Holloway College2 The search for CP violation with asymmetric e + e - collider Why ? How ? PEPII and the BaBar Experiment sin2  measurement: The golden modes: b -> ccs The Cabibbo-suppressed modes: b -> ccd The pure penguin modes: b -> sss sin2  eff measurement: CP asymmetries in  +  - and K +  -  +  0 and  0  0 decay rates CP asymmetries in  +  - and  + K - Conclusions Outline

3. November 26, 2002Fabrizio Salvatore, Royal Holloway College3 C and P symmetries Parity reversal ( P ): Inverts spatial coordinates r  - r p  - p And reverses helicity e - L  e - R Charge conjugation ( C ): Turns particle into anti-particle electron e -  e + positron B 0 (bd)  B 0 (bd) And preserves helicity!

4. November 26, 2002Fabrizio Salvatore, Royal Holloway College4 The laws of physics for matter and anti-matter are nearly identical. In the universe matter prevails over anti-matter. This asymmetry remains a mystery…. One essential ingredient is that CP must be violated (1967 A. Sakharov). CP violation occurs in the Standard Model It fails by several orders of magnitude to predict the matter/anti-matter asymmetry in the universe. There must be physics beyond the Standard Model Large potential for new discoveries CP violation : A cosmological need

5. November 26, 2002Fabrizio Salvatore, Royal Holloway College5 Physics principles: CP violation in the SM The only source of CP violation in the SM is the KM phase that appears in the CKM matrix CP from complex component of V ub and V td The Wolfenstein parameterisation

6. November 26, 2002Fabrizio Salvatore, Royal Holloway College6 The unitarity of the CKM matrix uctuct d s b apply unitarity constraint to pairs of columns ds* = 0 sb* = 0 db* = 0 (K system) (B s system) (B d system) These three triangles (and the three triangles corresponding to the rows) all have the same area. A nonzero area is a measure of CP violation and is an invariant of the CKM matrix.

7. November 26, 2002Fabrizio Salvatore, Royal Holloway College7 The unitarity triangle in B d system uctuct d s b Orientation of triangle has no physical significance. Only relative angle between sides is significant. (1,0)    (,)(,) (0,0) V ub * V ud V cb * V cd V tb * V td V cb * V cd apply unitarity constraint to these two columns Goal: to over-constrain sides and angles! ,  and  constrained by CP asymmetries in B decays

8. November 26, 2002Fabrizio Salvatore, Royal Holloway College8 Time-dependent CP violation from B 0 -B 0 mixing f CP b d d b u,c,t top quark box introduces : V tb V td *  m d = m H - m L WW Direct CP violation if multiple amplitudes with different phases Purely CP violation in interference of decays with and without mixing

9. November 26, 2002Fabrizio Salvatore, Royal Holloway College9 Experimental requirements 1.Large sample of events with a B fully reconstructed in a CP eigenstate, eg J/  K s WHAT? 3.Measure the decay time difference between the two B decays  t). 2.“Tag” the initial flavour of the fully reconstructed B at  t=0. HOW? 1.Low branching ratios : high luminosity facility. 2.At  (4S) pairs of B mesons are produced as a coherent state. Use particle id to identify decay products of the other B in the event. 3.Use asymmetric beam energies to create  (4S) moving through the lab.  t   z and  z is then sufficiently large to be measurable.

10. November 26, 2002Fabrizio Salvatore, Royal Holloway College10 2 current facilities: PEP-II (BaBar) @ SLAC KEKB (Belle) in Japan BB threshold B meson production at B-Factories Off On PEP-II B A B AR Cross Sections at  (4S):

11. November 26, 2002Fabrizio Salvatore, Royal Holloway College11 PEPII performances Peak luminosity: 4.60 x 10 33 cm -2 s -1 (exceeded design goal 3.0 x 10 33 ) PEP-II delivered 99 fb -1 BaBar recorded94 fb -1 For sin2  and sin2  used: On peak81 fb -1 88M BB pairs Off peak10 fb -1 Peak luminosity: 4.60 x 10 33 cm -2 s -1 (exceeded design goal 3.0 x 10 33 ) PEP-II delivered 99 fb -1 BaBar recorded94 fb -1 For sin2  and sin2  used: On peak81 fb -1 88M BB pairs Off peak10 fb -1

12. November 26, 2002Fabrizio Salvatore, Royal Holloway College12 B A B AR Detector SVT: 5 double side layers. 97% efficiency, 15  m z hit resolution (inner layers, perp. tracks) Momentum resolution (SVT+DCH):  (p T )/p T = 0.13 %  p T + 0.45 % DIRC: 144 quartz bars. Provide K-  separation 4.2  @ 3.0 GeV/c  2.5  @ 4.0 GeV/c EMC: 6580 CsI(Tl) crystals. Energy resolution:  E /E = 2.3 %  E -1/4  1.9 %

13. November 26, 2002Fabrizio Salvatore, Royal Holloway College13 B 0 -B 0 events at the  (4S) resonance Boost:  = 0.55 Coherent BB pair B0B0 B0B0  K-K- Flavour tag and vertex reconstruction    KSKS  Z  4S  B tag B rec Exclusive B meson and vertex reconstruction Start the Clock Compute A(  t)=f + - f - f + + f -

14. November 26, 2002Fabrizio Salvatore, Royal Holloway College14 Vertexing algorithm B rec vertex from charged B rec daughters B Tag vertex from: All charged tracks not in B rec, constrain with B rec vertex, beam spot, and  (4S) momentum High  2 tracks removed, to reject charm decays) Beam spot Interaction Point B REC Vertex B REC daughters B REC direction B TAG directionTAG Vertex TAG tracks, V 0 s z High efficiency: 95% Average  z resolution ~ 180  m (dominated by B tag vertex)  t resolution function measured using fully reconstructed B D (*)- h + (h + =  +,  +, a 1 + ) and B J/  K *0 (K *0 K +  - ) data events (B flav sample)

15. November 26, 2002Fabrizio Salvatore, Royal Holloway College15 Tagging algorithm  Algorithm based on neural networks:  inputs: leptons, K, slow  (D * decay) and high-momentum tracks 5 mutually exclusive categories: Lepton - isolated high-momentum leptons; kaon I – high quality K, correlated K and slow  (from D * ); kaon II – low quality K or slow  (from D * )  Inclusive – unidentified leptons, low quality K, high-momentum tracks; Untagged – not used for CP analysis b sc K-K- New and improved tagging method

16. November 26, 2002Fabrizio Salvatore, Royal Holloway College16  t resolution and dilution typical mistagging & finite time resolution perfect tagging & time resolution Need to know mistag fraction w and  t resolution function R in order to measure CP asymmetry. Can extract these from data with B 0 -B 0 mixing events.

17. November 26, 2002Fabrizio Salvatore, Royal Holloway College17 Use B flav sample to measure w and R B 0  D (*)-      a 1  N tagged =23618 Purity=84% B 0  J/  K *0 (K     N tagged =1757 Purity=96% B flav sample is x10 size of CP sample Fully reconstructed, self-tagged modes are used to determine the mis-tag fractions (w i ) and  t resolution function Apply B tag algprithm to the other B and fit for B 0 -B 0 mixing:

18. November 26, 2002Fabrizio Salvatore, Royal Holloway College18 Tagging performance from B tag sample ~1-2w CategoryEfficiency (  ) Mistag Fr. (w) Q=  (1-2w) 2 Lepton 9.1  0.23.3  0.67.9  0.3 Kaon1 16.7  0.29.9  0.710.7  0.4 Kaon2 19.8  0.320.9  0.86.7  0.4 Inclusive 20.0  0.331.6  0.92.7  0.3 Total 65.6  0.528.1  0.7 This new tagging method increases Q by 7% compared to the method used in our previous result: PRL87 (Aug 01).

19. November 26, 2002Fabrizio Salvatore, Royal Holloway College19 Tree level dominates and CP only from B 0 -B 0 mixing sin2  from charmonium states (b  ccs) f =  f e -i2   f =±1 B0B0 K0K0 B 0 -> J/  K s B 0 ->  (2S) K s B 0 ->  c 1 K s B 0 ->  c K s  f = -1  f = 1 B 0 -> J/  K L  f = 1- 2R T B 0 -> J/  K *0 (K *0 -> K s  0 ) R T = 16.0 + 3.5 % (PRL87)

20. November 26, 2002Fabrizio Salvatore, Royal Holloway College20 Recent addition: B 0  c K s where  c K + K -  0 or K + K s  - Event yields and purity Event SampleN tag Purity J/  K s (  +  - ) 97497% J/  K s (  0  0 ) 17089%  (2S) K s 15097%  c1 K s 8095%  c K s 13273% Total (  f = -1) 150692% J/  K L 98855% J/  K *0 (K s  0 ) 14781% All CP modes264178% Energy-substituted mass: Energy difference: J/K s ( +  - ) J/K s ( 0  0 ) (2S)K s cKscKs  c1 K s Total event yields

21. November 26, 2002Fabrizio Salvatore, Royal Holloway College21 sin2  samples: J/  K L and J/  K *0 J/K *0 (K s  0 )  f = +0.65±0.07 N tagged = 147 Purity = 81% J/ K L Signal J/  Bkg Fake J/  Bkg Data  f = +1 N tagged = 988 Purity = 55%  Use m B constraint to determine p KL  J/  background shape estimated from Monte Carlo  Fake J/  background shape estimated from data sidebands  Vector-Vector mode: mixture of CP+ and CP-  Use angular analysis to determine CP- fraction  Treat CP- component as dilution  effective  f

22. November 26, 2002Fabrizio Salvatore, Royal Holloway College22 Example for hadronic B decay B0  J/KSB0  J/KS m ES [GeV/c 2 ]  E [MeV] Side-band region (outside the signal region) is defined in order to estimate the backgrounds Signal region:

23. November 26, 2002Fabrizio Salvatore, Royal Holloway College23 Blind analysis method In time-dependent asymmetries, we use a technique that hides not only the result of the fit, but also the visual CP asymmetry in the time distribution. The statistical error on the asymmetry is not hidden. BABAR uses “blind” analysis strategies for the extraction of the time- dependent and time-integrated asymmetries in order to minimize possible experimenters bias.

24. November 26, 2002Fabrizio Salvatore, Royal Holloway College24 sin2  likelihood fit Simultaneous unbinned maximum likelihood fit of CP and mixing samples Fit Parameters34 total sin2  1B CP Mistag fractions w for B 0 and B 0 tags 8B flav Signal  t resolution function R 8B flav Background properties 17B CP +B flav (mostly from m ES sidebands in data) B lifetime fixed (PDG 2002)  B = 1.542 ps Mixing frequency fixed (PDG 2002)  m d = 0.489 ps -1

25. November 26, 2002Fabrizio Salvatore, Royal Holloway College25 sin2  = 0.723  0.158 sin2  result  f =-1  f =+1 sin2  = 0.755  0.074 sin2  = 0.741  0.067 (stat)  0.033 (sys) (hep-ex/0207042)

26. November 26, 2002Fabrizio Salvatore, Royal Holloway College26 Asymmetry in b  ccs modes with lepton tag sin2 = 0.79  0.11 Golden mode (cc) Ks with lepton tag only N tagged = 220 Purity = 98% Mistag fraction 3.3%    t 20% better than other tag categories

27. November 26, 2002Fabrizio Salvatore, Royal Holloway College27 sin2  fit results by decay mode Consistency of CP Channels: P(  2 ) = 57% Sin2  in various subsamples:

28. November 26, 2002Fabrizio Salvatore, Royal Holloway College28 Cross-check on data control samples Observed no asymmetry as expected

29. November 26, 2002Fabrizio Salvatore, Royal Holloway College29 Constraints in the (  ) plane One solution for  is in excellent agreement with measurements of unitarity triangle apex Method as in Höcker et al, Eur.Phys.J.C21:225-259,2001  =  (1- 2 /2)  =  (1- 2 /2)

30. November 26, 2002Fabrizio Salvatore, Royal Holloway College30 Search for new physics in (cc)K S events | f | = 0.948  0.051 (stat)  0.017 (syst) S f = 0.759  0.074 (stat)  0.032 (syst) If another amplitude that contributes with a different phase: In the measurement of sin2  we have assumed | f | = 1 (SM expectation) S f  -  f sin 2  C f  0 Fit | f  | and S f using the clean (cc)K s modes (  f =-1, N tagged = 1506, Purity = 92%): Consistent with the Standard Model expectation of | f |=1 and nominal fit sin2  = 0.755  0.074 for (cc)K s modes alone.

31. November 26, 2002Fabrizio Salvatore, Royal Holloway College31 B 0  D *+ D *- : same weak phase as b  ccs (tree level); small penguin contribution (<0.1 Tree); not CP eigenstate (needs angular analysis) The Cabibbo-suppressed modes (b  ccd ) N tagged = 102 Purity = 82% B0B0 D * - D * + B0B0 D * - D * + V cd R T = 0.07+0.06+0.03 | + | = 0.98  0.25 (stat)  0.09 (syst) Im( + ) = 0.31  0.43 (stat)  0.10 (syst) Im( + ) measurement ~2.7  from BaBar sin2  in charmonium, assuming no penguins. + Parameterize in terms of CP-odd (  ) and CP-even ( + ) components and use: |  |= 1, Im(  ) = -0.741 (hep-ex/0207072) If penguins are negligible, then Im( + ) = - sin2  stat error only

32. November 26, 2002Fabrizio Salvatore, Royal Holloway College32 B A B AR 81.3 fb  B A B AR 81.3 fb  sin2  from penguin mode B 0   K S Dominated by b  sss gluonic penguins |  K | = 1 fixed S  K = -0.18  0.51(stat)  0.07 (syst) C  K = -0.80  0.38(stat)  0.12 (syst) Small branching fraction O(10 -5 ) Significant background from qq continuum N(  K s (K s   +  - ) = 51 N(  K s (K s   0  0 ) = 13 Cross check on B +   K + : S  K = 0.26  0.27 If no new physics, S  K = sin2 Same Weak phase as b  ccs, but sensitive to new physics in loops

33. November 26, 2002Fabrizio Salvatore, Royal Holloway College33 sin2  from penguin mode B 0   ’ K S  “Internal Penguin” “Tree-level b->u” Very similar to  K S except for one additional complication – a tree-level b  u contribution. London and Soni estimate the relative size of the b  u tree to be |T/P|<0.02 (hep- ph/9704277) Beneke and Neubert estimate |T/P|  (8  3)% (hep-ph/0210085)

34. November 26, 2002Fabrizio Salvatore, Royal Holloway College34 sin2  from penguin mode B 0   ’ K S B A B AR 81.3 fb  B A B AR 81.3 fb  Signal

35. November 26, 2002Fabrizio Salvatore, Royal Holloway College35 Intriguing hint ? Present average for. ~ 2.7 sigma below charmonium modes If central value remains as is, this would become ~5 sigma by 2005

36. November 26, 2002Fabrizio Salvatore, Royal Holloway College36 Interesting new measurements are being obtained on the open charm modes: B 0  D *+ D *- (hep-ex/0207072) and b penguin modes: B 0  K 0 S (hep-ex/0207070) B 0  ’ K 0 S (hep-ex/0207070) Summary of sin2  results New measurement of sin2  from charmonium modes (88 x10 6 BB) Results have been improving by more than just luminosity gain No hints of physics beyond the Standard Model yet, but lots of opportunities to challenge the theory with the increasing event statistics in BaBar Million BB pairs July 00 Feb 01 July 01 Mar 02 July 02 sin2  = 0.741 ± 0.067 (stat) ± 0.033 (syst) PRL 89 (2002) 20

37. November 26, 2002Fabrizio Salvatore, Royal Holloway College37 sin2  from charmless B decays Penguin contribution is non-negligible measure sin2  eff + mixing decay B 0   +  - Tree (T) Penguin (P) need BF from B ->  +  -,  +  0 and  0  0 and isospin analysis to obtain  from  eff

38. November 26, 2002Fabrizio Salvatore, Royal Holloway College38 sin2  : B → , K , KK modes Small branching ratios (10 -5 -10 -6 ) lots of data needed use kinematic and topology of events to separate signal from light-quark bg Large background from continuum (qq) events Fisher discriminant: **   p*p* Ambiguity between  and K needs excellent particle ID (DIRC) Data sample: 88M BB events

39. November 26, 2002Fabrizio Salvatore, Royal Holloway College39  hypothesis K hypothesis K/p separation using the DIRC Double-gaussian PDFs built from the difference (  c –  c exp )/s(  c ) K/  separation and PDF parameters measured using fully reconstructed data For  =85%:  P(K->  ) = 1.7%  P(  ->K) = 2.7 % Identification of h + h’ - tracks as  or K using the angle  c measured in the DIRC

40. November 26, 2002Fabrizio Salvatore, Royal Holloway College40 Event yields and K  asymmetry Time-independent maximum likelihood fit to extract event yields and K  asymmetry no tagging or vertexing needed ModeYieldBR (10 -6 ) A CP (K  ) B→ B→  157 + 194.7 + 0.6 + 0.2 B→ KB→ K 589 + 3017.9 + 0.9 + 0.7 -0.102 + 0.050 + 0.016 B→ KKB→ KK 1 + 8< 0.6 (90% C.L.) Direct CP Preliminary Submitted to Phys Rev (hep-ex/0207055)

41. November 26, 2002Fabrizio Salvatore, Royal Holloway College41 m ES and  E distributions Preliminary Signal events are selected in the (m ES,  E) plane same as for sin2  measurement B o ->  KK

42. November 26, 2002Fabrizio Salvatore, Royal Holloway College42 1 ps Projection in sample of  -selected events qq+ K  S  and C  measurement Time-dependent unbinned maximum likelihood fit Same tagging and vertexing procedure as for sin2  S  = 0.02 + 0.34 + 0.05 C  = -0.30 + 0.25 + 0.04 Preliminary Submitted to Phys Rev (hep-ex/0207055)

43. November 26, 2002Fabrizio Salvatore, Royal Holloway College43 Extraction of  from  eff Need to measure: B + ->  +  0, B 0 ->  0  0, B 0 ->  0  0 Grossman-Quinn bound Otherwise, put limit on BR(B 0 ->  0  0 ): Isospin analysis Gronau and London, Phys.Rev.Lett 65, 3381 (1991) B ->  +  -,  +  0 and  0  0 decays related by isospin (gluonic) penguins contribute only to I=0  +  0 has I=2 only tree amplitude only (|A     A   ) 2  eff = 2  +  

44. November 26, 2002Fabrizio Salvatore, Royal Holloway College44 B + ->  +  0 and B + ->K +  0 branching ratio B + ->  +  0 has pure tree amplitude and no CP expected Usual charmless two-body analysis B 0 ->  +  - bg reduced by a Fit region e  e  → qq  ModeYieldBR (10 -6 )A CP B→B→ B→KB→K Simultaneous fit to   /K   hep-ex/0207065 tight cut on  E Preliminary

45. November 26, 2002Fabrizio Salvatore, Royal Holloway College45 B 0 ->  0  0 branching ratio Preliminary B 0 ->  0  0 yield determined by unbinned ML fit: @ 90% CL |  –  eff | < 51 0 Central value for BR: If BR as high as its central value, Grossman-Quinn bound not adequate isospin analysis is necessary hep-ex/0207063 Small signal expected Flavour tagging and event topology used to reduce qq bg B + ->  +  0 bg reduced using a cut on m(  +  0 ) and  E

46. November 26, 2002Fabrizio Salvatore, Royal Holloway College46 B0->  h: direct and indirect CP measurement  CP BR = (28.9+5.4+4.3)x10 -6 NOT CP eigenstate insensitive to CP  K self tagging Direct CP A CP and C = 0 Indirect CP S = 0

47. November 26, 2002Fabrizio Salvatore, Royal Holloway College47 Event yields and charge asymmetry Clear B 0 ->  signal Maximum likelihood fit to extract yields and charge asymmetry: Preliminary hep-ex/0207068 Validation test: fit  B and  m d using data B 0 /B 0 ->     B 0 /B0->      B = (1.540 + 0.014) ps  m d = (0.503 + 0.006) ps -1 World Average

48. November 26, 2002Fabrizio Salvatore, Royal Holloway College48 Time-dependent asymmetry Preliminary hep-ex/0207068 dominated by uncertainties on B background components expected ~0.4 (from naïve factorization) sensitive to strong phase differences

49. November 26, 2002Fabrizio Salvatore, Royal Holloway College49 Direct CP violation Direct CP can be expressed using the asymmetries:  meson from spectator quark  meson from spectator quark Using previous results and their correlations: A +- = - 0.82+0.31(stat)+0.16(syst) A -+ = - 0.11+0.16(stat)+0.09(syst)

50. November 26, 2002Fabrizio Salvatore, Royal Holloway College50 Summary of sin2  and direct CP violation results Charmless two-body decays: branching ratios and CP asymmetries in B 0 ->  +  -, K +  - and K + K - (hep-ex/0207055)  branching fractions needed to extract  from  eff computed: upper limit on BR(B 0 ->  0  0 ) (hep-ex/0207063) B + ->  +  0 and K +  0 branching ratios (hep-ex/0207065) still too early for significant constraint: Charmless three-body decays: first CP asymmetry measurement for B 0 ->  and B 0 ->  K  (hep-ex/0207068) |  –  eff | < 51 0 A +- = - 0.82+0.31(stat)+0.16(syst) A -+ = - 0.11+0.16(stat)+0.09(syst) no evidence for large direct or indirect CP violation in  +  -

51. November 26, 2002Fabrizio Salvatore, Royal Holloway College51 Conclusions (I) Extremely productive time for B physics with BaBar ! More still to come ! BUT New measurement of sin2  from charmonium modes Submitted to PRL July 17, 2002 (hep-ex/0207042) sin2  = 0.741 ± 0.067 (stat) ± 0.033 (syst) BaBar and Belle’s sin2  results have convinced the physics community that CKM is the dominant source of CP violation Several preliminary results of asymmetry in b->ccd and b->sss published recently CP asymmetry in B 0 /B 0 ->    +  decay (hep-ex/0207068) No evidence for large direct or indirect CP violation in B 0 ->  +   Measurement of the branching ratios for B + ->  +  0,K +   (hep-ex/0207065) Upper limit on BR(B 0 ->  0  0 ) and constraint on |  -  eff | (hep-ex/0207063) (hep-ex/0207055)

52. November 26, 2002Fabrizio Salvatore, Royal Holloway College52 Conclusions (II) More exciting physics results are on their way ! A lot more to do with the 100 fb -1 of data already recorded and those still to come in the next run starting this fall higher precision in the sin2  measurement measurement of  and   better knowledge of |V ub | and |V cb |  rare decays (possibility to probe new physics)  Charm physics (D 0 mixing, CP, ….)  tau results other very interesting physics results:

53. November 26, 2002Fabrizio Salvatore, Royal Holloway College53 Future:  and sin(2  +  ) (I) Preliminary B ->D *  /  /a 1 h+h+ W+W+ B0B0 b d d u d c D *- V ud V cb * Cabibbo allowed W+W+ B0B0 b d d c d u h-h- V cd V ub * Cabibbo suppressed D *+ Time evolution of B 0 ->D *- h + and B 0 ->D *+ h - related to sin(2  +  ) For precise measurement, need many events D * a 1 mode has the largest BR (~1.3%) use partial reconstruction: Only the slow  from D * ->D 0  decay and the  /  /a 1 (a 1 ->  0  ) are reconstructed If only the D 0 is missing, in the  (4S) frame the B direction lies on the surface of a cone Averaging over this surface, the missing mass m miss can be defined P *( , ,a 1 ) P*P* P * D0 P*BP*B Signal: m miss peaks to D 0 mass Bg events: broader distribution

54. November 26, 2002Fabrizio Salvatore, Royal Holloway College54 B ->D *   t(ps) Continuum Comb. BB Peak. BB Signal Nsig = 6971+241 First steps: B 0 lifetime using D *  and D *  decays  B = 1.616+0.064 (stat) +0.075 (syst) ps hep-ex/0203036  B = (1.540 + 0.014) ps World Average  B = 1.510+0.040 (stat) +0.038 (syst) ps hep-ex/0203038 Validation for the partial reconstruction technique B ->D *  Nsig = 5521+251  B extracted using an unbinned maximum likelihood fit data sample 20.7 fb -1

55. November 26, 2002Fabrizio Salvatore, Royal Holloway College55 data sample 20.7 fb -1 PDG: (1.30+0.27)% BF = (1.20+0.07+0.14)% Signal yield: 18400+1200 Preliminary hep-ex/0207085 data on-reso (off-reso subtr.) signal+BB bg MC BB bg MC only D * a 1 branching fraction measurement Continuum background rejected using a neural network technique  exploit the different topologies between qq events (jet structure) and B events (spherical) m miss distribution obtained from off-reso data subtracted from that obtained on on- reso result fitted with a combination of: BB Monte Carlo events signal Monte Carlo events B ->D * a 1

56. November 26, 2002Fabrizio Salvatore, Royal Holloway College56 Future:  and sin(2  +  ) (II)  with B ->D 0 (CP) K W+W+ B+B+ b u u u s c K+K+ D0D0 V us V cb * Colour allowed B+B+ b u u c K+K+ D0D0 W+W+ u s V cs V ub * Colour suppressed data sample 75 fb -1 hep-ex/0207087 Preliminary

57. November 26, 2002Fabrizio Salvatore, Royal Holloway College57 Summary: B ->D 0 (CP) K and B 0 ->D * (n)  Analyses just begun, still lot of work to do ! B -> D 0 (CP) K mode: ratio of branching fraction for B->D 0 K and B->D 0  modes first measurement of CP asymmetry in B->D  (CP)  K  (hep-ex/0207087) B -> D * (n)  mode : B0 lifetime using D *  and D *  decays (hep-ex/0203038, hep-ex/0203036) branching fraction of B 0 -> D * a 1 decay channel (hep-ex/0207085) R= (8.31+0.35+0.20)% A CP = (0.17+0.23 ) +0.09 -0.07 BF = (1.20+0.07+0.14)%  B = (1.533+0.034+0.038) ps Combined measurement:

58. November 26, 2002Fabrizio Salvatore, Royal Holloway College58 C and P violation CP is also violated: Small CPV effects discovered in the neutral Kaon system (1964) Final experimental confirmation from NA48 and KTev Example of C and P violation in Weak interactions: the neutrino CP  L C P X

59. November 26, 2002Fabrizio Salvatore, Royal Holloway College59 CP violation in the B system  Eg CPV through the interference between mixing and decay amplitudes   f is a phase which changes sign under CP. CP-violating differences between the decay rates of a particle and that of its antiparticle can arise from the interference between two decay amplitudes with relative CP-violating and non-CP-violating phases.

60. November 26, 2002Fabrizio Salvatore, Royal Holloway College60 Sources of Systematic Error  sin2  Description of background events0.017 CP content of background components Background shape uncertainties Composition and content of J/  K L background0.015  t resolution and detector effects0.017 Silicon detector alignment uncertainty  t resolution model Mistag differences between B CP and B flav samples0.012 Fit bias correction0.010 Fixed lifetime and oscillation frequency0.005 TOTAL0.033 Steadily reducing systematic error:July 2002 = 0.033 July 2001 = 0.05

61. November 26, 2002Fabrizio Salvatore, Royal Holloway College61 CP composition of B 0  D *+ D *- We measure CP odd fraction (corrected for acceptance) to be small: R  = 0.07  0.06 (stat)  0.03 (syst)

62. November 26, 2002Fabrizio Salvatore, Royal Holloway College62 The Cabibbo-suppressed modes (b  ccd) (II) D* _D* _ D+D+ D* _D* _ B0B0 B0B0 D*+D*+ D _ D*+D*+ D+D+ CP conjugation strong phase D * D 56 fb -1 N tagged = 85 Purity = 52% S +- = -0.43  1.41  0.20 C +- = 0.53  0.74  0.13 S -+ = 0.38  0.88  0.05 C -+ = 0.30  0.50  0.08 Update to full data set in progress B 0  D *+ D - : Not a CP eigenstate possible strong phase contributions; different decay time distributions for : B 0  D - D *+ B 0  D *- D +

63. November 26, 2002Fabrizio Salvatore, Royal Holloway College63 (hep-ex/0207058) The Cabibbo-suppressed modes (b  ccd) (II) B 0  J/   0 : also color-suppressed Comparable tree and penguin contribution ~ O( 3 ) V cd Tree: ~V cb V cd * Penguin:~V cb V cd * + V ub V ud * N tagged = 49 Purity = 59%  f = + 1

64. November 26, 2002Fabrizio Salvatore, Royal Holloway College64 Validation of tagging, vertexing and fit procedure Use B 0 ->K  events: T=tag charge, Q=K charge  same sample as for CP asymmetries   B and  m d floating in the fit  B = (1.56 + 0.07) ps  m d = (0.52 + 0.05) ps -1  B = (1.540 + 0.014) ps  m d = (0.503 + 0.006) ps -1 World Average Projection in sample of  -selected events

65. November 26, 2002Fabrizio Salvatore, Royal Holloway College65 The history of sin2  measurement in BaBar a)“Osaka 2000” measurement (hep-ex/0008048) Only J/  K s and  (2s) K s. b)1 st Paper (PRL 86 2515, 2001) Added J/  K L. Simultaneous sin2  and mixing fit. c)2 nd Paper (PRL 87 201803, 2001) Added J/  K *0 and  c K s. Better vertex reconstruction. Better SVT alignment and higher K s efficiency for new data. d)Winter 2002 (hep-ex/0203007) Improved event selection. Reprocessed 1 st 20 fb -1. e) Current measurement (PRL 89, 2002) Improved flavor tagging. One more CP mode:  c K s. a b c d e