BaBar & Belle: Results and Prospects

1. BaBar & Belle: Results and Prospects Claudio Campagnari University of California Santa Barbara

2. Physics Program at the B-Factories • Comprehensive investigation of CKM structure of SM • CP-Violation (CPV) a key ingredient • CPV from just one phase in SM • Other measurements very important too • Rare B-meson decay (but also D, t) • Sensitive to new particles in loops • Indirect signature of new physics? • B (and D and t) decay dynamics

3. Today:Concentrate (mostly) on measurements related to the unitarity triangle

4. B-factories and the unitarity triangle (h,r) Buln B(p,r,w)ln B0 pp, rp,.. B-mixing B(r,w)g a B0 J/y Ks, D*D*,… Bcln BD(*)ln g b (0,0) (1,0) BKp,DK,D*p,… Both angles and sides of U.T. are accessible through measurements at the B-factories

5. Outline • BaBar and Belle • Luminosity, present and future • Lifetimes and mixing • Sin2b results • Working towards sin2a • Comments on g • Vub • Conclusions Note: averages from Heavy Flavor Averaging Group (unless otherwise specified)

6. Belle: 132 fb-1 Record lumi: 9.5 1033 BaBar: 117 fb-1 Record lumi: 5.2 1033 Note: 100 fb-1 ~ 108 106 BB pairs B-factories performance

7. B-factories prospects • Luminosities are improving • PEPII up to ~ 2 to 4 1034 cm-2 sec-1 • KEKB perhaps as high as 1035 • Detectors need modest upgrades to cope • Should have ~500 fb-1 by 2005-2006, 1000-2000 fb-1 by end of decade • Now have ~ 100 fb-1 per expt

8. 8K events 12K events Mixing and lifetimes Results based on large samples of • Fully or partially reco. hadronic decays • Fully or partially reco. D* l n • Dileptons 29 fb-1

9. Dt Distributions  Lifetimes Dt = proper time difference between the decay times of the two B-mesons Dt resolution of ~ same order of magnitude as lifetime t0 = 1.554  0.030  0.019 psec t- = 1.695  0.026  0.015 psec

10. Adding Tagging Information Dmd = 0.516  0.016  0.010 ps -1 30 fb-1

11. Lifetimes results summary • Belle and BaBar now dominate world averages • Improvement by x2 over pre B-factory era • Order 1% uncertainty on lifetimes and ratio

12. Partial averages from F. Ronga CKM Workshop03 Mixing results summary } LEP+CDF 0.497§0.014 ps-1 } BaBar + Belle 0.502§0.006 ps-1 World Average 0.502§0.006 ps-1 Dominated by BaBar & Belle 3% precision!

13. Mixing and Lifetimes - Prospects • Hard, precision measurements • Many are based on only a fraction of the available dataset • Statistical uncertainties still significant • room for improvement Theoretical uncertainties limiting factor in ability to extract clean CKM information

14. The measurements of mixing and lifetimes provide the foundations for the time dependent CPV measurements that follow

15. S C General time-dependent formalism Interfering amplitudes with different CP-violating (weak) phases can give a non-zero CP asymmetry. For B0! fCP: Then, when one of the interfering amplitudes is B-mixing with Only one decay amplitude (or all decay amp. same CKM phase): C=0 and S gives clean CKM phase information

16. Sin2b in b ! c c s • Golden modes: • clean theory • “relatively easy” experiment • Tree and leading penguin have same phase • sinDmDt coeff. measures sin2b cleanly • Not just J/y KS: • Also y’ KS, cc1 KS, hc KS (CP=-1) • J/y KL (CP=+1) • J/y K*0 (Mixed CP)

17. Event Samples Clean ~2K KS sample + ~ 500 KL events with ~ 60% purity 1.6K events ~500 signal ev.

18. Events with KS Events with KL Dt distributions and asymmetries CP=+1 CP=-1

20. Summary of sin2b in b  ccs 7.5% precision

21. Fit for cosDmDt coefficient, extract |l| 5% precision consistent with |l|=1 (as expected in SM)

22. Sin2b from other modes • b ! ccd • D(*) D(*) and J/yp0 • penguins with different phases can be important • b ! s (penguin) • f KS, h’ KS etc • sensitive to new physics in the b!s penguin Results from these modes are very much statistics limited

23. J/yp0 ~ 40 ev D*D* ~ 130 ev f KS ~ 36 ev h‘ KS ~ 150 ev

24. C = 0 if no penguin S = - sin2b if no penguin B0! J/yp0

25. C = 0 if no penguin S = sin2b if no penguin B0! D*D* • Vector-Vector final state: could have CP even and odd components • Both BaBar and Belle measure mostly CP even • BaBar fits S and C S = -0.32 § 0.43 § 0.13 C = +0.02 § 0.25 § 0.09

26. , f b ! s modes B !f KS B !h‘ KS • Like fKS but also u-tree • Still, S~sin2b • Same CKM structure • as J/y KS • u-penguin down by ~1/50 • Expect S=sin2b to 5%

27. ‘ Expectation from J/yKS bs penguin: S coefficient (sin2b) bs penguin average 0.18  0.20 ~ 2.5 s from ccs modes

28. Sin2b prospects • Sin2b in b  ccs is already a precision measurement • But still statistically limited • Will be improved • Measurements in other modes will improve as luminosity • Maybe faster, as techniques improve • Improved results in the b  s modes will be particularly interesting!

29. u b t d p- p- d u b u u p+ d d p+ d d B0 B0 Sin2a • In the absence of penguins, sin2a from B0!p+p- asymmetry • BR of B0! K+p- and B+!p+p0 tell us that interference between P and T is large • In principle isospin analysis of p+p-, p+p0, and p0p0 allows for clean extraction of a • In practice p0p0 very hard

30. B ! hh Branching Ratios (x 10-6) Averages from J. Olsen, CKM Workshop 2003

31. Time dependent fits to p+p- 78 fb-1 ~ 106 events 84 fb-1 ~ 160 events

32. S C p+p- Fit Results Belle rules out CP conservation (C=S=0) at 99.93% C.L. BaBar is still consistent with C=S=0 The discrepancy is at ~ 2-2.5s level

33. Sin2a from rp • a from full, time dependent, tagged, Dalitz plot analysis of p+p-p0 • Hard analysis • For starters, BaBar • Quasi two body analysis, only r+p- and r-p+ • Also r+K- and r-K+ • BF(B0rK)= (7.31.31.3) 10-6 • BF(B0rp)= (22.61.82.2) 10-6

34. B  rp ~ 430 events ACP = -0.18 § 0.08 § 0.03Ã time integrated term C = 0.36 § 0.18 § 0.04 S = 0.19 § 0.24 § 0.03 • 2s CPV effect • first step towards full • Dalitz analysis

35. Sin2a- Prospects • Clean extraction without theoretical assumptions will be hard • If B0 p0p0 very small, bounds on sin2a could become quite useful • We will most likely see CPV (maybe we are already seeing it) • but we will have a hard time disentangling the weak phases

36. What can we say about g ? • B !pp vs Kp • From tree-penguin interference • Needs some theo assumptions • B ! DK • Theoretically clean • Interference between bu(cd) and bc(ud) • B D(*)p, D(*)r, D(*)a1 • Theoretically clean • Sin(2b+g)

37. s K- u - D 0 b b c B - D0 B - s K- c u u u u u Vub ~ eig B  DK • Information on g through interference in • final states common to D0 and D0 (e.g. pp, KK..) • Several variants on the market • prospects look a little brighter, as color • suppression not as large as previously thought • Measurements of various BR done or in progress • First asymmetry measurements

38. g from B  DK, an example D is CP-odd or CP-even neutral D combination with strong phase

39. DK Dp D  K+K-, p+p- D  KSp0, Ksf, KSw, KSh, KSh‘ no useful constraints yet

40. g - Prospects • Many methods, many theoretically clean • Problems: • Need a lot of luminosity! • Often methods have ambiguities • g, g + 45o, g + 90o, etc. • Will need to combine many channels • It will be a long and arduous journey • We are taking the first steps • Many more B  D(*)K(*) modes have been/are being measured • Not sure where we will end up • But it should be fun

41. Vub from b  u l n Two complementary approaches • Reconstructed exclusive states • B  p l nB r l nB w l nB  h l n • Theoretical uncertainties • Lattice could eventually come to the rescue • Inclusive b  u l n • Theoretically cleaner • Experimenters make cuts into phase space • introduce theoretical uncertainties

42. Vub: Exclusive Decays • Branching ratios: BaBar, Belle, Cleo • General agreement • Working to combine into single Vub • Typical individual measurement d|Vub| ~ 20%

43. Compilation from Gibbons, CKM Workshop 2003 Exclusive Branching Ratios x 10-4 x 10-4

44. Inclusive decays: b  u l n E(X) M2(X) q2(ln) E(lepton) X=hadronic syst in bX l n From Muheim, CKM Workshop 2003: Blue lines indicate bc l n regions

45. b  u l n: new expt. technique Breco Brecoil D* Y(4S) l p • Fully reconstruct one B • Then look only at what’s left • Reduce combinatorics • Know momentum vector of recoil • Important for kinematic reconstruction • Reduce continuum n

46. S/B~0.3 Lepton pl>1.0 GeV/c S/B ~ 2.5 MES [GeV] • B  D(*) np • Efficiency only 0.4% • But statistics are OK • M(X) reconstruction • Belle, similar technique • with B  D(*) l n MX < 1.55 GeV Signal 167 ± 21 events

47. b  u l n inclusive: summary • Individual measurements • in agreement • ~ 15-20% uncertainty each • improvement on LEP

48. Vub Summary • Much progress is being made • Very active area, both theory and experiment • Lattice improvements soon • Want to go well below 10% uncertainty for Unitarity Triangle constraints

49. Conclusions • The B-factories have gone through a very successful first three years • Today I showed you only a small fraction of their physics program, there is much more • We are looking forward to increases in luminosity, eventually x10-20 more data • The SM is still alive and well, but we’ll continue poking at it

50. THE END