Recent Achievements of Belle experiment

1. Recent Achievements of Belle experiment KEKPH07 2007/Mar./2nd Kenkichi Miyabayashi (Nara Women’s Univ.) for Belle collaboration

2. As of 2007/Feb./28,… During 2006/2007, 40 papers have been published or submitted(more than 200 from the beginning). ↓ Apparently it is impossible to mention all of them, so … http://belle.kek.jp/bdocs/b_journal.html

3. Outline • CP violation measurements for unitarity angles • B decays with “Missing Energy” • Activities on other Υ states • Future prospect and Summary

4. KM scheme & Unitarity triangle In the quark mixing matrix, an irreducible complex phase is there. → CP violation. (a) On complex plane, a triangle is formed. B meson is a good probe. (b) (g)

5. Angle measurements B-B mixing (box) Decay via b → u (tree) (a) (g) (b) Decay via b → c (tree) How about b → s (penguin)?? b → d (penguin) is also participating in some cases → direct CPV.

6. In order to perform such study, … PDG2006 The B decay modes for CP violation studies have small branching fraction(i.e. B is so heavy that there are so many decay modes). → Need quite a lot of B. → Need to measure time evolution of B.

7. KEKB accelerator Lum./day 1fb-1/day 700fb-1 535M BB by 2006 summer Int. lum. 8GeV(e-)X3.5GeV(e+) 3km double ring Peak lum.>1.7X1034cm-2s-1

8. Belle detector Aerogel Cerenkov Time Of Flight CsI calorimeter S.C. solenoid 1.5T 3.5GeV e+ 8GeV e- Central Drift Chamber Silicon Vertex Detector KL μ system

9. Time dependent CPV CP side (B to fCP) In order to see CPV by interference between decay and mixing. Tag side (the other B) Dz=bgcDt, bg=0.425 Dz

10. Measurement of sin21 (1) Decay Vtd* (2) Decay with mixing Vtd* Interference between (1) and (2) results in CP violation. We have to wait to let (2) contribute, i.e. t=0. In SM, SfCP=-CP sin21,where CP =-1 for CP odd, +1 for CP even, AfCP=0. Theoretical uncertainty is ~0.01.

11. Reconstruction of B0 → J/ K0 Nsig = 6512 Purity 59 % CP even Nsig = 7482 Purity 97 % CP odd In Υ(4S) rest frame, Mbc = { (ECM/2)2 - (S Pi)2}1/2 KL; only direction known. B0 → J/ KL has less purity. PRL98,031802(2007)

12. _ B0 tag B0 tag Time-dependent decay rates Asymmetry=-CP sin21sin(mt) Opposite asymmetry corresponding to CP ! PRL98,031802(2007)

13. B0 tag _ B0 tag sin21; J/ KS & J/ KL combined sin21 = +0.642±0.031±0.017 AJ/K = +0.018±0.021±0.014 PRL98,031802(2007)

14. Before/After B factories Before B factories Recent World Average

15. 1 in penguin decays as well as New Physics in the loop; CPV deviation from J/ K0? SM penguin; No complex phase in decay. Look time-dependent CPV in such decay modes! A series of this kind of B decays; ’K0, K0, KSKSKS, KS, KS0, K+K-KS.

16. B0 → ’ KS, KS, KSKSKS Nsig=1421±46 Plots show signal enriched sample by event shape variables. Nsig=307±21 Nsig=185±17 PRL98,031802(2007) Mbc(GeV/c2)

17. Reconstruction of B0 → ’ KL, KL Nsig=454±39 Nsig=114±17 PRL98,031802(2007) After background subtraction.

18. B0 → ’ K0 CPV in 5.6! First CPV observation in penguin decays! sin21eff = +0.64±0.10±0.04 A’K = -0.01±0.07±0.05 PRL98,031802(2007)

19. See other modes sin21eff = +0.50±0.21±0.06 A = +0.07±0.15±0.05 sin21eff = +0.30±0.32±0.08 A = +0.01±0.20±0.07 PRL98,031802(2007)

20. See other modes(cont.) f0(980)KS KS K+K-KS (excl. KS) KS0 hep-ex/0609006

21. Compare tree and penguin Theory predicts positive shift, while measurements tend to be negative shift(av. 2.6 deviation). More statistics needed to have conclusive results.

22. Another tree: B0 → D+D- caused by b → ccd Tree (a) dominant → SDD becomes -sin21, ADD = 0. Penguin (b) is b → d, complex phase due to Vtd → may cause Direct CPV. From 535M BB, Nsig = 150±15 has been obtained. hep-ex/0702031

23. B0 → D+D-; t distribution B0(t)→ D+D- B0(t)→ D+D- SDD=-1.13±0.37±0.09 ADD=+0.91±0.23±0.06 hep-ex/0702031 Evident Direct CPV(3.2)! Need to update all the b → ccd modes(D*+D*-, J/0, etc) to have a comprehensive understanding of this transition.

24. – – – – – – t Vud u u b b d d p/r V*ub – B0 B0 t b d p/r B0 d d Mixing diagram Decay diagram (tree) 2 measurement If tree only, Sf is directly connected to sin22 and Af=0. V*tb Vtd Vtd V*tb There are 3 possibilities; ,, .

25. B0→p+ p- Nsig=1464±65 S=-0.61±0.10±0.04 A=+0.55±0.08±0.05 C.L. contour (Background subtracted) Large Direct CPV App=0 ; Not only Tree but also Penguin →Spp=(1-App2)1/2 sin2(f2+q) , how to solve?

26. Extract f2; isospin analysis M. Gronau and D. London, PRL 65, 3381 (1990) B0→p+p-, p0p0, B±→p±p0 branching fractions, and B0→ p0p0 Direct CPV are used as inputs to solve this relation. SU(2) braking effect is still much smaller than measurements’ errors.

27. 2 constraint only with B→  Constraint is not stringent by  alone. → need  and . 2

28. B→  V2 It is B→ VV decay, admixture of CP-odd and CP-even, in general. V1 B H+ Transverse polarization(CP-odd) H− H0 Longitudinal polarization(CP-even) |H0|2 + | H+ |2 + | H−|2 =1 • There are two miracles; • fL=0.968±0.023, i.e. almost pure CP eigenstate. • B0→ 00 is small, i.e. small penguin pollution. Quite high ability to constrain 2!

29. B0→  B0(t) B0(t) S=+0.19±0.30±0.07 A=+0.16±0.21±0.07 Note; CPV is small, but consistent with 2=90° because S = sin22 in “tree dominance”. hep-ex/0702009

30. 2 by B→  This region is ruled out.

31. Time-dependent Dalitz Plot Analysis (TPDA) of B0→ ( Since  decays into , ther ethree possibilities; B0→ +-(+), -+(-) and 00(0). Final state commonly +-0 → resolve by Dalitz distribution(26 parameter fit!). Then, 2 is extracted by the amplitudes; With 449M BB, Nsig=971±42 (B0→ +-0) hep-ex/0701015

32. TDPA of B0→ ( +-(+) Isospin relation results in “pentagon” in this mode. -+(-) 68°< 2 < 95° at the 68% C.L. 00(0) hep-ex/0701015 (=m)

33. About 2 All the measurements favor about 90° as 2. • B→  sets window around 90°. • B→  pinpoints the favored value inside the window. • B→ isexpected to rule out solutions of 2~0 and ~180° with higher statistics.

34. 3 by B±→ D(*)K(*)± Dalitz analysis D(*)0 and D (*)0decay into common final state →Vcb and Vub interfere：f3 Here, select D→KSp+p−, B+ decay amplitude = f(m+2, m−2) + r exp(+if3+id) f(m−2, m+2) B− decay amplitude = f(m−2, m+2)+ r exp(−if3+id) f(m+2, m−2) (m+=KSp+, m−=KS p− inv. mass) → extract r, f3, d by B+ and B− Dalitz Plots.

35. B±→ D(*)K(*)± reconstruction B±→ D(KSp+p−)K± Nsig=331±23 B±→ D*0[(KSp+p−)p0]K± Nsig=81±11 B±→ D(KSp+p−)K(*)± Nsig=54±8

36. Dalitz Plot B±→ D(KSp+p−)K± B+ B− After background subtraction and acceptance correction, these distributions are fitted with the model taking 18 resonant and non-resonant amplitudes. B+ B− B±→ D*0[(KSp+p−)p0]K± Model uncertainty：Can be reduced by charm meson data. (Eventually ~2°) f3=53° +15°/-18° ±3°±9°

37. H+/W+ t+ B±→ ± While, charged Higgs can interfere helicity-suppressed W exchange. In SM, caused by annihilation diagram; → determination of B decay constant fB.

38. Full reconstruction technique One of the Bs is fully reconstructed (by D, D, etc. ) to tag B production/flavor(charge)/momentum. Decays of interests BXu l n, BK n n BDtn, tn B e- (8GeV) e+(3.5GeV) Υ(4S) p full (0.1~0.3%) reconstruction BDp etc. B Single B meson beam in offline ! Powerful tool for B decays with neutrinos! Note that it can be done only at e+e- B-factories.

39. Evidence of B±→ ± Try to reconstruct  by the particles other than the fully reconstructed B daughters via , e, , 0 and  modes. Remove the calorimeter(ECL) hits associated with  daughters. The remained ECL energy(EECL) becomes zero for the signal (only (s) remain). fB= PRL97,251802(2006)

40. Constraint on charged Higgs Excluded Using SM estimation; BrSM=(1.59±0.32±0.24)×10-4 fB |Vub| fB from HPQCD |Vub| from HFAG Much stronger constraint than those from energy frontier exp’s.

41. Running on Υ(3S) Try to hunt Υ(3S)→ Υ(1S)  to see Υ(1S) decays into a light dark matter. invisible Dashed line: expectation with Br(Υ(1S) → )=6×10-3 Peak is consistent with the background due to Υ(1S) → l+l- escaping detector acceptance Br(Υ(1S)→ invisible)<2.5×10-3 @90% C.L. hep-ex/0611041, to appear in PRL Recoil mass distribution

42. Running on Υ(5S) PRL98, 052001(2007) Ds J/ Bs(*)Bs(*) production ratio, inclusive Ds, D and J/ measurements have been done. Histograms:continuum

43. Future prospect

44. Example of physics reach LHC find mass spectrum of SUSY particles, while SUSY breaking scenario would be identified by CPV, i.e. measurement of coupling and its phase!

45. Summary • Three angles (1, 2, 3) are fairly well-measured to perform quantitative test of KM scheme, more efforts to be continued to hunt New Physics effect. • With full reconstruction technique, rare decays with missing are to be measured. Evidence of B±→ ±has been obtained. • Running on other Υ states have been done successfully, accumulating more in future upon a good idea. • In LHC era, Super B-factory could identify SUSY breaking scenario through its program of measurements of Phases from CPVNew Physics.

46. Backup slide

47. Decay angle definition

48. Reconstruction of CP side B meson Example; B0→ J/y KS Utilize Υ(4S)→ BB kinematics Mbc = { (ECM/2)2 - (S Pi)2}1/2 → Signal peaks at B mass (5.28GeV). DE = S Ei - ECM/2 → Signal peaks at zero. DE(GeV) Mbc(GeV)

49. Vertex reconstruction(Dt measurement) BB is boosted with bg=0.425: Dt is obtained by z. Utilize IP-profile a lot. • CP side vertex • J/y、p+p-,etc. charged tracks. • In KS→p+p- case, extrapolate • momentum vector toward IP-profile. • Tag side vertex • Tracks with impact parameter w.r.t. CP side vertex < 500mm • Veto KS daughters, remove poorly reconstructed tracks by c2. • Resolution function • Detector resolution, D(*) life, B momentum into account.

50. Flavor tagging (B or B?) • Lepton charge • high-p lb c ln • intermed-p l+s l n • Hadron charge • high-p p+ B0D(*)p+, D(*)r+, etc. • intermed-p K+ K+ X, pp0 • low-p p D0p By calculating Likelihood, q =+1(B0) , − 1 (B0) (Tag side) r = 0(no flavor info.) 〜 1(perfectly confident tagging).