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B physics at Belle

B physics at Belle. Koji Hara (Nagoya University). New results of tauonic B decays B  tn and BD tn. Workshop "New Developments of Flavor Physics" 2009 March 9-10, 2009. Belle detector. Ares RF cavity. e + source. e - (8.0GeV) × e + (3.5GeV) ⇒ U (4S) →BB

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B physics at Belle

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  1. B physics at Belle Koji Hara (Nagoya University) New results of tauonic B decays Btn andBDtn Workshop "New Developments of Flavor Physics" 2009 March 9-10, 2009

  2. Belle detector Ares RF cavity e+ source • e- (8.0GeV) × e+ (3.5GeV) • ⇒U(4S) →BB • ⇒Lorentz boost: bg = 0.425 • Finite crossing angle • ~11mrad ×2 • Operation since 1999. • L peak = 1.71x1034cm-2s-1 KEKB & Belle SCC RF(HER) Total: 895 fb-1 U(4S): ~720 fb-1 U(5S): ~52.6fb-1 U(3S): 2.9 fb-1 U(2S): 7.1fb-1 U(1S): 5.7fb-1 Yb scan: 8.1fb-1 Off-peak: ~83 fb-1 ARES(LER) The World Highest Luminosity

  3. BelleDetector Extreme forward calorimeter He/C2H6 4 lyr DSSD

  4. B+t+n Introduction • Leptonic decays proceed through W boson annihilation in the Standard Model • Decay rate simply related to B meson decay constant fB and |Vub| • Charged Higgs contribution enhance/reduce the Br [Wei-Shu Hou Phys. Rev. D48, 2342 (1993)] • CP Violation may be sensitive to “unparticle” physics [ R. Zwicky, Phys.Rev.D77036004(2008), C.-S. Huang and X.-H. Wu, Phys.Rev.D77,075014(2008)] b u W/H  

  5. e+ (4S) B- B+ ne n n B++, +e+e B-X Btn Analysis Concepts More than 2 neutrinos appear in B tn decay • Require no particle remain after removing products oftagging B and the particle(s) from Btn decay Possible only in B factory Most powerful discriminant variable: Extra calorimeter energyEECL Tagging side : Semileptonic or Hadronic B Decay Signal side : Detect t daughter particle(s)

  6. Previous B+t+nMeasurements Belle Hadronic • Belle Hadronic B tag (449x106 BB pairs) [PRL 97, 251802 (2006)] • 3.5s evidence B(Btn)=[1.79 (stat) (syst) ] x 10-4 • BaBar (383 x 106 BB pairs) [PRD 77, 011107(R) (2008)], [PRD 76, 052002 (2007)] • Hadronic B Tag • Semileptonic (BDln X) Tag X: g, p0, not reconstructed explicitly • 2.6s excess B(Btn)=[1.2±0.4(stat)±0.3(bkg)±0.2(syst)]×10-4 +0.56 +0.46 -0.49 -0.51 BaBar DlnX BaBar Hadronic B=3x10-3 Signal B=1x10-3 Signal Need more statistics to establish B+t+n Decay New Belle Result with D(*)ln tag using 657M BB pairs

  7. Signal Selection Concept Though Br(BD(*)ln)is large (~17%), S/N is expected to be worse than S/N of hadronic B tags. • We only use clean decay modes with high Br x e. • Tagging Side • B-  D*0l+n, D0ln D*0D0p0, D0g • D0K-p+,K-p+p-p+, K-p+p0 • ReconstructD*0ln explicitly  preventadditional p0 (g) fromcontaminating EECL • Signal Side 1 prong decay • B+t+n t enn, mnn, pn • Require No additional charged tracks or p0

  8. Selection Criteria • Tagging side • Identified using a kinematic relation • Optimized to maximize in EECL<0.2 GeV • separately for tlnn and pn modes • Signal side • Nsig extracted from EECL • Clear Signal and BG separation expected D*ln tag, tpn + Data +BG D*ln tag, tlnn + Data +BG MC expectation BG Events / 0.05 GeV signal (B =1.79x10-4) EECL(GeV)

  9. Semileptonic Tag Bn Result [arXiv: 0809.3834, BELLE-CONF-0840] 3.8σ significance including systematics. Dominant systematic error for B(Btn): BG MC Statistics (12%), Tagging Efficiency(12%) Peaking BG Uncertainty (8%) Confirmation of previous Belle result with hadronic tags (more precise) Above SM expectation, discrepancy ~1.6σ (CKMfitter 2008 prediction)

  10. Determination of fB • Product of B meson decay constant fB and CKM matrix element |Vub| • Using |Vub| = (4.47±0.30)×10-3 from Belle BXuln inclusive [Belle preliminary, CKM2008] fB = 216  22 MeV (an unquenched lattice calc.) [HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]

  11. Constraint on Charged Higgs rH=2.110.75 95% C.L.

  12. B→Dn Introduction • Semileptonic decay sensitive to charged Higgs Ratio of t to m,e could be reduced/enhanced significantly c b   W/H Compare to B→τν T.Miki, T.Mimuta and M.Tanaka:hep-ph 0109244. • Smaller theoretical uncertainty of R(D) For B→τν, There is O(10%) fBuncertainty from lattice QCD • Large expected Br (Ulrich Nierste arXiv:0801.4938.) • The decay shape of 3 body decay can be used to discriminate W+ and H+ • Sensitive to different vertex Bt n: H-b-u, BDtn: H-b-c

  13. Previous B→D(*)tn Measurements • Belle B→D*τν B→Dtn was not measured Belle inclusive B tag : 5.2σ observation • Babar B→D(*)τν Babar full reconstruction tag :

  14. BDtnAnalysis Method Similar to Btn analysis π K B B Υ(4S) e νe ντ ντ Tagging Side Signal Side (B→Dtn) (B→Hadronic mode) • Require no remaining particles in the event using EECL • Additional discriminant variable: Missing Mass square MM2of the event • to separate BDln BG (MM2 ~ 0) from signal (MM2>0)

  15. Tag Side Reconstruction fully reconstruct B0,B+ 657x106BB Total B+→147 modes B0→133 modes (Belle preliminary) (Belle preliminary) N=1.01x106 eff. = 0.31% Purity = 58% N=6.05x105 eff. = 0.18% Purity = 51% B+ B0 • Beam constraint Mass :

  16. PCM(τ→X) Selection of B→D(*)tn • D(*) decay modes • τ selection arbitral -signal -Dlν -D*lν -Other BG e,μ with lower momentum No additional charged particles and π0 remain in the event • Dτν Selection -Main background: Semileptonic B decays ( D(*)lν ) Extra calorimeter Energy(EECL)Select signals using Missing Mass square (MM2)、 EECL MM2 Separate D(*)lν and signal No remaining particles arbitral events/0.1GeV -signal -Dlν -D*lν -Other BG -signal -Dlν -D*lν -Other BG -signall -Dlν -D*lν -Other BG -signall -Dlν -D*lν -Other BG orbital

  17. B→Dn Result • Plots are projection in the signal enhance region • Plots are projection in the signal enhanced region B+→Dτν EECL MM2 ●data - Dτν - D*τν - BG ●data - Dτν - D*τν - BG events/0.4GeV2/c4 Observed Clear Signal events/0.1GeV (EECL<0.2GeV) (MM2>2.0GeV2/c4) (3.8σ) First evidence GeV GeV2/c4 B0→Dτν (2.6σ) EECL MM2 ●data - Dτν - D*τν - BG ●data - Dτν - D*τν - BG (Belle preliminary) events/0.4GeV2/c4 events/0.1GeV (MM2>2.0GeV2/c4) (EECL<0.2GeV) GeV GeV2/c4

  18. B→D*n Result B+→D*τν EECL ●data - Dτν - D*τν - BG MM2 ●data - Dτν - D*τν - BG • Plots are projection in the signal enhanced region events/0.4GeV2/c4 events/0.1GeV (MM2>2.0GeV2/c4) Observed Clear Signal (EECL<0.2GeV) GeV GeV2/c4 B0→D*τν EECL MM2 ●data - Dτν - D*τν - BG ●data - Dτν - D*τν - BG events/0.4GeV2/c4 events/0.1GeV (Belle preliminary) (EECL<0.2GeV) (MM2>2.0GeV2/c4) GeV GeV2/c4

  19. Determination of R(D(*)) (preliminary) Deviation from the SM expectation B+→Dτν: 1.6σ B0→Dτν: 0.5σ Consistent within errors  Working on charged Higgs constraint. Branching fraction (preliminary) +0.41 +0.24 Br(B+→Dτν) = 1.51 ± 0.15 [%] -0.39 -0.19 +0.46 +0.13 Br(B0→Dτν) = 1.01 ± 0.10[%] -0.41 -0.11 +0.69 +0.40 Br(B+→D*τν) = 3.04 ± 0.22 [%] -0.66 -0.47 +0.75 +0.31 Br(B0→D*τν) = 2.56 ± 0.10[%] -0.66 -0.22 (first error is stat second is systematic, third is D(*)ln Br error)

  20. Summary • New measurement of Btn with semileptonic tagging method confirms the evidence obtained by Belle haronic tag. Update of hadronic tagging will also come soon. • First BDtn measurement in Belle has been performed. We obtained first evidence of B+D0t+n decay. • Measurement of tauonic B decays are now well established. They are giving tight constraints on charged Higgs. • Future measurements in Super B Factory will be strict tests of new physics beyond the SM.

  21. Specific Luminosity With Crab Crossing @ KEKB Crab Crossing Data Simulation head-on 3.06 bucket spacing Simulation 22 mrad 22 mrad crossing Not as high as the expectation of simulation Still need more study to achieve the goal (2x specific luminosity) Crab crossing since January 2007

  22. Selection Criteria and Efficiency • For tmnn, enn modes • Dominant BG: true D(*)lnu tagged B-decays  looser tagging selection • -2.1<cosqBDL<1.3, -2.6<cosqBD*L<1.2, 0.5<P*ltag<2.5 • P*lsig > 0.3 • For tpn mode • Suppress continuum and combinatorial BG  tighter tagging selection • -1.1<cosqB(*)DL<1.1,1.0<P*ltag<2.2 • 1.0<P*psig < 2.4 • |cosqthrust| < 0.9 • Reconstruction efficiency Including Br of t decay modes and tagging side efficiency • tenn mode: 6.0 x 10-4 • tmnn mode: 3.8 x 10-4 • tpn mode: 4.9 x 10-4 34th International Conference on High Energy Physics

  23. Systematic Errors of Yield BG PDF Shape +18.1 -17.2 Signal PDF Shape +3.1 -3.2 Br of Peaking BG +6.4 -13.0 Rare B,buln,t pair BG +5.9 -5.9 Efficiency Ratio +0.5 -0.6 Total +20.3 -22.3 34th International Conference on High Energy Physics

  24. Br Systematic Error +(%) -(%) (Error for Efficiency) MC stat 0.9 0.9 PID 1.3 1.3 Br of t 0.4 0.4 Tracking 1.0 1.0 Tagging Efficiency 11.6 11.6 Signal Yield 13.2 14.7 NBB 1.4 1.4 Total 21.2 22.2 34th International Conference on High Energy Physics

  25. Systematic error

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