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Measurement of | V ub | at Belle

32 nd International Conference on High Energy Physics. Measurement of | V ub | at Belle. Toru Iijima Nagoya University for Belle Collaboration. August 17, 2004. S/N. Full recon. good. Semilep. decay. advanced n recon. Belle (m X ,q 2 ) PRL92,071802. mod. trad. n recon. poor.

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Measurement of | V ub | at Belle

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  1. 32nd International Conference on High Energy Physics Measurement of |Vub| at Belle Toru Iijima Nagoya University for Belle Collaboration August 17, 2004 ICHEP2004

  2. S/N Full recon. good Semilep. decay advanced n recon. Belle (mX,q2) PRL92,071802 mod. trad. n recon. poor Lum. low middle high Eff. • In this talk, we report measurements of • Inclusive B→Xu l n • with fully reconstructed tag. • Exclusive B→Xu l n • with semileptonic decay tag. with 140fb-1 (152M BB) Results are preliminary Introduction • |Vub| measurement • Crucial to test the standard model of the CP violation. • Both inclusive/exclusive B→Xu l n decays are useful. • Belle explores B tagging technique to extract B→Xu l n in good quality. • Good signal-to-noise • Sufficient statistics ICHEP2004

  3. p p Tagging side Btag→D(*)p/r etc. K Btag e- e+ Υ(4S) Bsig Signal side Bsig→Xu l n q2: Leptonic inv. mass 2 mX: Hadronic inv. mass Inclusive B→Xu l nw/ Fully Reconstructed Tag • Tagging side: • Full reconstruction of Btag using hadronic decay modes. • Signal side: • Lepton Detection • Neutrino reconstruction using Pmiss, Emiss. • Reconstruction of (mX, q2) ICHEP2004

  4. Full Reconstruction of Btag Inclusive B→Xu l n • Reconstructed modes (180 in total) 7 modes 6 modes 2 modes • Mbc(beam constrained mass) distribution 140fb-1 data B0 tag. 1.58 ×105 eff.=0.21% purity = 47% B+ tag. 2.47 ×105 eff.=0.33% purity = 50% Signal region: Mbc > 5.26GeV/c2, -0.2 GeV < DE < 0.05 GeV ICHEP2004

  5. Expected MM2 dist. b→u b→c • Reduction of bc background • Number of leptons Nl= 1 • Total net charge ∑Qi=0 • Missing mass -1.0<MM 2<0.5 GeV2 • Missing mom. Direction cosqMM < 0.95 • Number of kaons NK+ = NKS = 0 -4 -2 0 2 4 6 8 10 12 14 MM2 (GeV2/c2) Phase space cut to minimize theory error mX < 1.7 GeV/c2, q2 > 8 GeV2 ※ same as our previous (mX,q2) measurement with simulated annealing [PRL 92, 071802 (2004)] Reconstruction of Signal Side Inclusive B→Xu l n Semileptonic lepton selection • Lepton momentum Pl> 1.0 GeV/c • Lab. angle 26 ~ 140deg. + J/y veto, conversion veto etc. Normalization to B→Xl n ICHEP2004

  6. mX distribution with Btag bkg. Subtracted. Signal Yield Extraction Inclusive B→Xu l n • Fit Mbc distribution in each mX region with Gaussian+’Argus’ to subtract the combinatorial background in the Btag sample. • Fit the obtained mX distribution with expected b →u and b → c distribution. Nb→u = 174±26 Mbc distribution for each mX region mX<1.7GeV/c2 q2>8GeV2 Expected dist. of b→u b→c Btag background 0 0.5 1.0 1.5 2.0 mX (GeV/c2) • The number of semileptonic leptons is extracted by similar fitting on Mbc before the b →u selection cut. Nsl = (5.07±0.4)×104 ICHEP2004

  7. mX distribution (q2>8GeV2) q2 distribution (mX>1.7GeV/c2) Expected dist. of b→c b→u Expected dist. of b→u b→c mX (GeV/c2) -5 0 5 10 15 q2(GeV2) 20 0 0.5 1.0 1.5 2.0 2.5 3.0 Event Distribution in mX and q2 Inclusive B→Xu l n • Event distribution in mX and q2 with the normalization fixed to the fitting with the coarse bin. 140fb-1 Subtracted with the Expected b→c bkg. ICHEP2004

  8. Partial branching fraction 140fb-1 preliminary (PDG2004) stat. syst. b→u b →c mX < 1.7 GeV/c2, q2 > 8 GeV2 Partial Branching Fraction Inclusive B→Xu l n • Relative partial branching fraction • Corrections: • Unfolding the mX /q2 resol. 0.984±0.014 • b→ u selection efficiency: 0.274 • Full recon. efficiency ratio: 0.75±0.048 • Fraction of semileptonic leptons with Pl > 1.0GeV/c ICHEP2004

  9. from fu error PDG formula +latest HQ parameters stat. syst. b→u. b →c. fu Br→|Vub| 140fb-1 preliminary |Vub| Determination Inclusive B→Xu l n • Extrapolation to the total br. • New determination of b-quark shape function (SF) parameters from Belle’s B →Xsg photon spectrum. + Higher order correction (FN →BLL) + Contribution from sub-leading SF + W.A. A.Limosani, T.Nozaki Hep-ph/0407052 ICHEP2004

  10. Exclusive B→Xu l nw/ Semileptonic DecayTag • New method for clean extraction of B→ p l n , r l n decays. D(*) Tagging side Btag→D(*) l n Btag “Double semileptonic” decay. e- e+ Υ(4S) Bsig Signal side Bsig→p, r l n p, r ICHEP2004

  11. Tag side reconstruction 4 decay modes 7 decay modes Signal side reconstruction or Kinematics of double semileptonic decay Back-to-back correlation of the two B constrains their direction to the intersection of the 2 cones. To have intersection, must be Analysis Method Exclusive B→Xu l n ICHEP2004

  12. Calibration with Bsig→D*ln Decays Exclusive B→Xu l n • Validity of the method for double semileptonic decay detection has been tested with x2 distribution M(K+p-p-) on the signal side Nobs=147±12 ( Nexpected =165) Dots: Data Histo: MC x2 M(Kpp) GeV/c2 • The ratio Nobs/Nexpected = 0.89 ±0.08 is used to correct the MC efficiency for p l n and r l n detection. The method works ! ICHEP2004

  13. Fitting results for all q2 data. 140fb-1 p l n (82±13) II I x2 dist. for p mass region (I) x2 dist. for r mass region (II) r l n (65±20) other Xul n BB x2 x2 mX GeV/c2 p l ndecays are cleanly extracted ! Signal Extraction Exclusive B→Xu l n • We extract p l n / r l n signals simultaneously by fitting 2D (mX, x2) distribution. • Fitting components: p l n, r l n, other Xu l n, BB background. • PDF’s are based on MC. • Constraint for extracted Br: Br(p l n)+Br(r l n)+Br(other Xu l n )=Br(Xu l n ) ICHEP2004

  14. q2:8-16GeV2 q2>16GeV2 q2<8GeV2 mX dist. for three q2 intervals Extracted q2 dist. mX (GeV/c2) □ISGW II p-l+n r-l+n ○ Ball’01 △UKQCD ◇Melikhov’98 At the present accuracy, the obtained q2 dist. does not exclude any tested models □ISGW II ○ Ball’01 △UKQCD FF-dep. 140fb-1 Preliminary Extraction of q2 Distribution Exclusive B→Xu l n • q2 distribution is extracted by fitting the (mX,x2) distribution for three q2 intervals. ICHEP2004

  15. w/ unquenched LQCD[FNAL/HPQCD] • Preliminary results reported at Lattice’04. • FNAL’04 • HPQCD 140fb-1, preliminary 4th error from FF-dep. in Br is small for p l n data |Vub| from B0→p- l+n Exclusive B→Xu l n • |Vub| determined from B>16GeV2 (B0→p- l+n ) with lattice QCD. • w/ quenched LQCD [FNAL/JLQCD/APE/UKQCD] Average ICHEP2004

  16. Summary We have obtained preliminary |Vub| results from • Inclusive B→Xu l n w/ fully reconstructed tag. • Results are compatible and consistent with the previous exp’s. • Exclusive B→Xu l n(B0 → p l n ) w/ semileptonic decay tag. • Results are compatible and consistent with the previous exp’s and inclusive results. • New method for clean signal extraction has been demonstrated. • These measurements are promising approach at B-factories in the coming years ! Belle |Vub| ICHEP2004

  17. Backup Slides ICHEP2004

  18. Systematic Uncertainties Dln (rD =1.19±0.19) D*ln (rA1=1.51±0.13) D**ln ... 5.6% ... 3.9% ... 1.6% Inclusive B→Xu l n bc MC statistics = 15% model dep. = 5% bu MC statistics = 4% model dep. = 4.2% Variate inclusive parameters within errors Detector sim. for bc & bu MC= 6.5% Correlated errors, added/subtracted in linear for the two MC’s Subtracting: Lept. sel. = 1%  clusters = 1% Adding: Kaon ID = 6% tracking = 2% Systematic error of Refreco and Relept ... 6.4% ICHEP2004

  19. Systematic Uncertainty Exclusive B→Xu l n Major contribution • D*lncalibration • Statistics of detected D*ln 8.3% • Error of Br(B0D*ln) 4.3% • BB background shape tested DB(pln) (DB(r l n)) in MC by • removing charged track by 1% -4.2(+23.5) % • removing p0 by 3%-1.1(+12.8) % • Replacing K with p by 2% -0.5(+16.6) % Significant change in DB(r l n), due to the broad width of r meseon. ICHEP2004

  20. BpForm-Factor from LQCD Exclusive B→Xu l n • Four quenched calculations from FNAL, JLQCD, APE and UKQCD (used in CLEO2003). • Average • Preliminary unquenched results from FNAL and HPQCD (reported at Lattice’04). • FNAL (M.Okamoto) • HPQCD(J.Shigemitsu) Include 15% quenching error ( given for q2>16GeV2 ) ICHEP2004

  21. Error of FF from Unquenched LQCD Exclusive B→Xu l n • FNAL’04 • Statistical ~10% • Lattice-continuum matching ~7% • Chiral extrapolation ~6% • Discritization ~5% • HPQCD • Statistical ~5% • Higher oder operator matching ~9% • Chiral extrapolation ~5% • Relativistic+discritization ~5% Number given by M.Okamoto (FNAL) and J.Shigemitsu (HPQCD) in private communications. ICHEP2004

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