1. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 1 B semileptonic decays from Belle n Introduction –weak interaction –Quark mixing & CKM matrix n Current status of measurements n Conclusions Youngjoon Kwon ( Yonsei Univ)

2. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 2 Fundamental Interactions

3. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 3 Weak interactions n mediated by weak gauge bosons

4. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 4 W  and Z 0 productions n First observed at the CERN collider in 1983

5. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 5 Z and W masses

6. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 6

7. 7 Weak interactions at low energy Considering W-exchange only, for

8. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 8 The fundamental fermions 1st 2nd 3rd generations

9. 9 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Lepton universality  Do all leptons and quarks carry the same unit of weak charge?  YES, for leptons and NO for quarks  First, let’s consider a muon decay  low energy process (q 2 ~ m  << m W )  specified by the Fermi constant: G F (~ g 2 /m W 2 )  dimensional analysis from full calculation (V  A)

10. 10 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Lepton universality  Now consider the tau (  ) lepton decay

11. 11 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Lepton universality  Again, from the  decay Since

12. 12 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Universality of weak interactions?  Do all leptons and quarks carry the same unit of weak charge?  Yes, for leptons and no for quarks  for quarks, the couplings to the weak gauge bosons depend on the quark flavors, due to “quark-mixing”  CKM mechanism

13. 13 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Universality of W.I. for quarks?  Consider the (semileptonic) weak decay  Assuming universality of weak decays of quarks, we expect both decays would happen in similar rate, but...

14. 14 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Universality of W.I. for quarks?

15. 15 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Universality of W.I. for quarks? So, what are we going to do? No universality for weak interaction? It was also noticed that the value of the Fermi constant G F deduced from nuclear b-decay was slightly less than that obtained from muon decay.

16. 16 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Cabibbo theory  Try to keep the universality, but modify the quark doublet structure…  Assume that the charged current (W  ) couples the “rotated” quark states  where d’, s’ (weak interaction eigenstates) are linear combinations of mass eigenstates d, s

17. 17 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Cabibbo theory  What we have done is to change our mind about the charged current: “Cabibbo-favored” vs. “-suppressed”  effective weak coupling for  S=0 (d  uW) is cos  c  effective weak coupling for  S=1 (s  uW) is sin  c

18. 18 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Cabibbo theory (Ex) What is the relationship between the weak couplings for muon decay (G  =G F ) and nuclear  -decay (G  ) ?

19. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 19 Features of SM interactions n Leptons do not have strong interactions n Quarks & Leptons do not change its flavor when interacting with neutral gauge bosons –quarks do not change flavor under strong int. –leptons & quarks do not change flavor when interacting with  or Z 0 –leptons & quarks change flavor only when interacting with W , and only within its family WW tb' W+W+

20. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 20 Cabibbo theory for 3 generations n Then how does b decay at all? Note: b  W  t but m(t) >> m(b) n For quarks, –mass eigenstates  weak interaction eigenstates –flavor mixing through CKM matrix weak interaction eigenstates mass eigenstates

21. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 21 CKM matrix n CKM is 3x3 and unitary –only 3 generations in the SM n CKM is almost 1, but not exactly V ii  1, V ij  0 for i  j n How do we determine the CKM matrix elements?

22. 22 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Free parameters of the S.M. n 17 free parameters in the electroweak interactions – –3 lepton masses –6 quark masses –4 quark flavor mixing parameters (a.k.a. CKM) –m(Higgs) n 10 of these are related with “quark flavors” i.e. we don’t know much about flavor sector in the SM after all these years of learning...

23. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 23 Expt’l determination of CKM elements n V ud –from nuclear  -decay n V us –from –results of K + and K 0 decays agree n V cd –from charm meson production via neutrino scattering

24. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 24 n V cs –from semileptonic decay of D meson –unitarity constraint assuming only 3 generations gives a much tighter bound Expt’l determination of CKM elements

25. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 25 Expt’l determination of CKM elements n V cb : from and HQET

26. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 26 Expt’l determination of CKM elements n V ub : from

27. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 27 Expt’l determination of CKM elements n V tb : from t-quark decay, assuming only 3 generations at the Tevatron collider at Fermi Lab, top quarks are produced mainly in pairs Assuming one could obtain a pure sample of

28. B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 28 n V td and V ts (1) (2) V td (s)(s) (s)(s) Expt’l determination of CKM elements

29. 29 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) The Unitarity Trianlge * other triangles are difficult to measure Hoecker et al., CKM-fitter (2003)

30. 30 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Challenge of V ub Smallest in magnitude : O( l 3 ) –hence very difficult to measure n Contains complex phase –a source of CP violation in the Standard Model n No golden mode –neutrino –hadronic uncertainties –Challenging for both theory & experiment n Final testing ground for CKM mechanism

31. 31 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Issues in V ub measurement Use B  X u l n (semileptonic) –Cleaner, better understood than B  hadronic –More accessible than B  leptonic –Inclusive and Exclusive n Experimentally challenging n Tight selection criteria results in Limited phase space  Extra theoretical uncertainties (from extrapolation)

32. 32 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) CKM Reach Hadron facilities vs. Super B factories BTeV 10 7 s LHC-b 10 7 s BABAR BELLE (200 5) 10 35 10 7 s 10 36 10 7 s sin2  0.0110.020.0370.0260.008Equal Sin2”  ” 0.05 0.140.10.032Equal  B s (D s K) ~7 0 Had  B(DK) ~2 o ~20 0 1-2.5 o Equal Sin2  0.023 0.04 -- Had Br(B   0  0 ) -- ~20%14%6%e+e- Vub -- ~2.3% ~1% (sys)~1% (sys) e+e- (Table compiled by SBF E2 subgroup & E2 convenors) SBF numbers based on BABAR experience need simulations to estimate signal efficiencies & bkgds so that the comparison to BTeV/LHC-b is on an equal footing [Snowmass 2001]

33. 33 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) V ub from semileptonic B decays MXMX plq2plq2 n Charmless semileptonic B decay – best tree-level process for V ub n Inclusive BF – predicted by OPE & HQS

34. 34 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Reconstruction of M X and q 2 at U (4S) B opp B sig X u or X c Y(4S) q pXpX p Bsig p Bopp If all particles except neutrino are measured

35. 35 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) V ub from inclusive S.L. B ~10% ~80% ~15% Shape Function region: OPE fails and needs shape function 100 times larger b  c background must be reduced Cuts increase theoretical error due to extrapolation error 1) Lepton energy (End-point) 2) Leptonic invariant mass 3) Hadronic invariant mass Bauer, Ligeti and Luke PR D64,113004 (2001)

36. 36 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Existing analyses on M x (1) bg 0 -2 2GeV 2 b➝cb➝c CLEO hep-ex/0207064 Traditional n recon. - high eff. - poor S/N & Mx resol.

37. 37 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Existing analyses on M x (2) BaBar M X <1.55 GeV 175 events 89x10 6 BB events PRL 92,071802(2004) n Full-reconstruction method Fully reconstruct the opposite B => Measure all momenta in signal side => - good S/N & Mx resol. - poor eff. ~O(0.1%)

38. Inclusive B  X u l n with simulated annealing

39. 39 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Novel X u recon. by Belle n reconstruction by (E,p) miss n “simulated annealing” to separate the other particles as belonging to signal B (B sig ) and associated B (B opp ) –S. Kirkpatrick et al., Science 220, No.4598 (1983) n good effi. w/ reasonable M x resol. both S/N & d M x are worse than full recon. n Belle’s new result: PRL 92, 101801(2004)

40. 40 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) n 6 discriminants are used – p* B, E* B, cos  * B, N ch of the B opp in CM –Q B x Q l, MM 2 Xln (w/ E* B, M B of B opp fixed to known values) Using B  Xl MC, calculate PDFs for correct and random Xl combinations n Calculate W with two likelihoods L(correct) and L(random) n The most likely candidate combination is found by minimizi ng W using an approximate iterative algorithm based on simulated annealing Separation of two B meson decays by “simulated annealing”

41. 41 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Simulated Annealing W old W new Initial state Random config. XB opp Move random one particle between X and Bopp If Wnew Wold If Wnew>Wold, keep new configuration with probability of exp{-1000(Wnew-Wold)/Wold}, otherwise keep old configuration Repeat this process untill all particles are moved at least once One iteration In total 500 iterations are used

42. 42 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Selecting “particles” n Using only good quality tracks and clusters: Require |MM 2 |<1.5GeV 2 n Add back low quality tracks/clusters iteratively ; select combination with smallest |MM 2 |

43. 43 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Simulated Annealing – results After annealing(data) Correct combination(signal MC) Before annealing(data) After annealing(data) Before annealing(data)

44. 44 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Event Selection n Data sample –Belle data at the energy asymmetric e + e - collider KEKB –78.1 fb -1 on resonance (85  10 6 BB) taken at the  (4S) –8.8 fb -1 off resonance (taken at 60 MeV below the resonance) n Selection of the final candidate ○ W < 0.1 ○ 5.1 < E* B < 5.4 GeV ○ 0.25 < p* B < 0.42GeV ○ - 2 < Q l Q B < +1 ○ - 0.2 < MM 2 Xl < +0.4GeV 2 ○ |cos  Bl | < 0.8 (  Bl :angle between the thrust axis of B assoc and the lepton mom.) ….. suppress continuum background

45. 45 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) M X and q 2 Resolutions M x and q 2 resolution distributions for B  X u l signal MC events Simulated annealing results Correct particle assignment to X u  =0.34GeV  =1.6 GeV 2

46. 46 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Tests of validity 38K D*l 84K J/  X, J/  l  l  l  or  l   treated as Detection efficiency from MC is calibrated using the average efficiency ratio for these two control samples

47. 47 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Backgrounds n Signal region: M X 8 GeV 2 –8910 events observed n Background subtraction –Continuum b.g. = 251  48 events is estimated using off-resonance data. –B  X c l (dominant) and other BB backgrounds are estimated by MC. –MC is tuned by 2D-   fitting the Mx vs q2 distributions of MC events to those of the real data in the B  X c l dominated region (Mx >1.8 GeV). –In the fit, fractions for B  D (*) l  D** l  D (*)  l and the total rate for other BB backgrounds are floated. –BB b.g. in the signal region: 7283  130(fit)  63(MC stat) events Net signal : 1376  167(stat) events

48. 48 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Results Signal MC After b.g. subtraction q 2 >8GeV 2 M x <1.7GeV

49. 49 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.)  B (B  X u l ) for (M X 8 GeV 2 ) N2N2 N1N1 N3N3 generatedobserved Signal region n Signal MC: based on Fazio & Neubert (hep-ph/9905351) –Leading order in HQE with O(  s ) QCD correction –Including the shape function effect –m b =4.80  0.12 GeV,  =-0.30  0.11 GeV 2 (From CLEO data for E(  spectrum in b  s  and M x moments in b  cl  Unfolding: N true = N obs  F (F  1+N 2 /N 1 - N 3 /N 1 ) Efficiency correction:  B=0.5  N true /(  signal  r eff )/(2N B ) n N obs =1376  167(stat) F=0.938,  signal =0.578%, N B =85  10 6  B (M X 8 GeV 2 ) = (7.37  0.89(stat)  1.12(syst)  0.55(b  c)  0.24(b  u) )  10 -4

50. 50 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) n Systematic error (15%) –Dominated by distortion of M x and q 2 distributions due to imperfect detector simulation n Model dependence –B  X c l  Change the form factor parameters for Dl and D*l within the errors Change fraction of D 1 l and D 2 l in D**l by  –B  X u l  Change the parameters of the inclusive model within the errors Compare with a full exclusive implementation of the ISGW2 model  B (B  X u l n ) for (M X 8 GeV 2 )

51. 51 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Extraction of |V ub | Perturbative term Weak annihilation m b 1S Total 3%4%11.5%12.5% fufu (m b 1S ) -5/2 Total 5%6.5%11.5% Positive correlation BLL

52. 52 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Conclusion n Belle made the first measurement of Vub with simultaneous cuts on Mx and q2 Using a novel technique “simulated annealing” n The result is consistent with the previous measurements, with much more reliable theory error estimation

53. 53 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Epilogue n In the PDG2004 mini-review on V ub,

54. 54 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Variables to suppress b  c l n (10% phase sp.) (~80%) (~30%)

55. Inclusive B  X u l n with End-point

56. 56 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Main features OPE breaks down  need shape ftn.! Measure D B (B  X u e n, p e > p cut ) Kinematic selection  p e > p cut  p cut = 1.9, 2.0, 2.1, 2.2, 2.3 and 2.4 GeV/c No requirement other than on the signal electron  high statistics Large background from B  X c e n  bkg. sys. uncertainty

57. 57 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) b-quark Shape Function n What is it? –b-quark Fermi motion inside the B-meson n How to get it? –Universal at leading order for all b  light quark transitions –Use E( g ) in B  X s g

58. 58 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Three models for SF Neubert & Paz, hep-ph/0504071

59. 59 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.)

60. 60 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.)

61. 61 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Event Selection Hadronic events Electrons in the barrel region  eff. ~ 94%; fake rate ~ 0.13%  J/ y, y (2S), g, p 0 veto Continuum suppression  Fox-Wolfram moment  Fisher disc. for energy-flow variables  |cos q th | < 0.75  as q 2 independent as possible Background estimated by  b  c MC and Off-resonance Data  low-p region for check 1.5 < p e < p cut (GeV/c)

62. 62 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) E(e) spectrum for B  X u e n eff. corrected

63. 63 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) D B – partial BF Two methods for D B  V ub –Standard method (DFN, JHEP 9906, 017) –New method (BLNP, NP B699 (2004))

64. 64 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) V ub from D B DFN BLNP

65. Inclusive B  X u l n with Full-Recon.

66. 66 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) 4.2  10 5 evts./253 fb -1 effic. = 0.33% purity = 62% 2.5  10 5 evts./253 fb -1 effic. = 0.21% purity = 59% Full Reconstruction

67. 67 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Signal selection Lepton Selection p > 1 GeV/c leptons in the barrel region  J/ y, g, p 0 veto Correct charge for B+ candidate No other lepton For b  u Total charge = 0 No reconstructed K S or K  N sl = (9.15  0.05) x 10 4

68. 68 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Kinematic selections (New)

69. 69 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) (1) M X < 1.7 GeV –Each bin content is calculated from Mbc fit –2-component fit to extract N(b  u)

70. 70 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.)

71. 71 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) (2) M X 8 GeV 2

72. 72 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) (3) P + < 0.66 GeV –First measurement using P +

73. 73 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Signal Yield & D B

74. 74 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) V ub from D B n New method –V ub directly from D B R by Bosch, Lange, Neubert, Paz, NPB699 (2004) with an improved treatment of shape-function effects + weak annihilation effects estimated

75. Exclusive B  X u l n with S.L. tag

76. 76 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Experimental Strategy B   l /  l  (140fb -1 ) ICHEP04 preliminary hep-ex/0408145 B   l  (78fb -1 ) PRL 93, 131803 (2004) lowmiddlehigh poor mod. good S/N Eff. trad. recon. Full recon. advanced recon. D (*) l tag Lum. How well can we measure the q 2 dist. (for p l n ) ? +  l /  l (preliminary) Unique opportunity at e+e- B-factory!

77. 77 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Analysis Method 4 decay modes 7 decay modes Tag side reconstruction To have intersection, need Kinematics of double semileptonic decay Back-to-back correlation of the two B’s constrains their direction to the intersection of the 2 cones. or Signal side reconstruction 2-fold ambiguity  q 2 calculated neglecting the B motion in U (4S) q 2 resolution = 0.75 GeV 2

78. 78 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) The ratio N obs /N expected = 0.89  0.08 is used to correct the MC efficiency for p l n and r l n detection. Calibration with B sig → D*l Decays n Validity of the method for double semileptonic decay detection has been tested with M(K +  -  - ) on the signal side x B 2 distribution N obs =147  12 The method works ! Dots: Data Histo: MC ( N expected =165) M(K  ) GeV/c 2 xB2xB2

79. 79 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Signal Extraction n q 2 distribution is extracted by fitting the (m X,x 2 ) distrib. for three q 2 intervals. m X (GeV/c 2 ) ■ Fitting components: p l n, r l n, other Xu l n, and BB ■ PDF’s are based on MC. ■ Constraint for extracted Br: Br( p l n ) + Br( r l n ) + Br(other X u l n ) = Br(X u l n ) q 2 <8GeV 2 q 2 :8-16GeV 2 q 2 >16GeV 2 82  13 65  20

80. 80 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Results

81. 81 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) V ub from exclusive B  X u l n 140 fb -1

82. 82 B semileptonic decays Nov.28 – Dec.2, 2005 Saga-Yonsei Workshop Youngjoon Kwon (Yonsei Univ.) Belle V ub Summary