2004/8/17ICHEP20041 Measurement of |V ub | at Belle Toru Iijima Nagoya University for Belle Collaboration August 17, nd International Conference on High Energy Physics

2004/8/17ICHEP20042 Introduction |V ub | measurement Crucial to test the standard model of the CP violation. Both inclusive/exclusive B→X u l decays are useful. Belle explores B tagging technique to extract B→X u l  in good quality. Good signal-to-noise Sufficient statistics lowmiddlehigh poor mod. good S/N Eff. trad. recon. Full recon. advanced recon. Semilep. decay Belle (m X,q 2 ) PRL92, Lum. with 140fb -1 (152M BB) Results are preliminary In this talk, we report measurements of Inclusive B→X u l with fully reconstructed tag. Exclusive B→X u l with semileptonic decay tag.

2004/8/17ICHEP20043 Inclusive B→X u l w/ Fully Reconstructed Tag Tagging side: Full reconstruction of B tag using hadronic decay modes. Signal side: Lepton Detection Neutrino reconstruction using P miss, E miss. Reconstruction of (m X, q 2 )  Υ(4S) e-e- e+e+ B tag B sig  K m X : Hadronic inv. mass Tagging side B tag → D (*)  etc. q 2 : Leptonic inv. mass 2 Signal side B sig → X u l

2004/8/17ICHEP20044 Full Reconstruction of B tag Reconstructed modes (180 in total) 7 modes 6 modes 2 modes B 0 tag ×10 5 eff.=0.21% purity = 47% B 0 tag ×10 5 eff.=0.21% purity = 47% B + tag ×10 5 eff.=0.33% purity = 50% B + tag ×10 5 eff.=0.33% purity = 50% Inclusive B→X u l M bc (beam constrained mass) distribution 140fb -1 data Signal region: M bc > 5.26GeV/c 2, -0.2 GeV <  E < 0.05 GeV

2004/8/17ICHEP20045 Reconstruction of Signal Side Semileptonic lepton selection Lepton momentumP l > 1.0 GeV/c Lab. angle26 ~ 140deg. + J/  veto, conversion veto etc. Normalization to B→X l Inclusive B→X u l m X 8 GeV 2 Phase space cut to minimize theory error  same as our previous (m X,q 2 ) measurement with simulated annealing [PRL 92, (2004)] Reduction of b  c background Number of leptonsN l = 1 Total net charge∑Qi=0 Missing mass-1.0<MM 2 <0.5 GeV 2 Missing mom. Directioncos  MM < 0.95 Number of kaonsN K + = N KS = MM 2 (GeV 2 /c 2 ) Expected MM 2 dist. b → u b → c

2004/8/17ICHEP20046 Signal Yield Extraction Fit M bc distribution in each m X region with Gaussian+’Argus’ to subtract the combinatorial background in the B tag sample. Fit the obtained m X distribution with expected b → u and b → c distribution. N b→ u = 174±26 N sl = (5.07±0.4)×10 4 Inclusive B→X u l The number of semileptonic leptons is extracted by similar fitting on M bc before the b → u selection cut. m X <1.7GeV/c 2 q 2 >8GeV 2 Mbc distribution for each mX region mX distribution with Btag bkg. Subtracted. Expected dist. of b → u b → c B tag background m X (GeV/c 2 )

2004/8/17ICHEP20047 Event Distribution in m X and q 2 Event distribution in m X and q 2 with the normalization fixed to the fitting with the coarse bin. Inclusive B→X u l 140fb -1 q 2 distribution (m X >1.7GeV/c 2 ) Expected dist. of b → u b → c q 2 (GeV 2 ) m X distribution (q 2 >8GeV 2 ) Expected dist. of b → c b → u m X (GeV/c 2 ) Subtracted with the Expected b → c bkg.

2004/8/17ICHEP20048 Fraction of semileptonic leptons with Pl > 1.0GeV/c Partial Branching Fraction Relative partial branching fraction b→ u selection efficiency: Full recon. efficiency ratio: Corrections: Unfolding the m X /q 2 resol.0.984±0.014 (PDG2004) stat.syst.b→ub → c Partial branching fraction 140fb -1 preliminary m X 8 GeV 2 Inclusive B→X u l 0.75±0.048

2004/8/17ICHEP20049 |V ub | Determination Extrapolation to the total br. New determination of b-quark shape function (SF) parameters from Belle’s B → Xs  photon spectrum. + Higher order correction (FN → BLL) + Contribution from sub-leading SF + W.A. Inclusive B→X u l A.Limosani, T.Nozaki Hep-ph/ from f u error +latest HQ parametersPDG formula stat.syst. b→u.b → c.fufu Br→  |V ub | 140fb -1 preliminary

2004/8/17ICHEP Exclusive B→X u l w/ Semileptonic Decay Tag New method for clean extraction of B→  l l  decays. Υ(4S) e-e- e+e+ B tag B sig  Tagging side B tag → D (*) l Signal side B sig →  l D (*) “Double semileptonic” decay.

2004/8/17ICHEP Analysis Method  decay modes  decay modes Tag side reconstruction  o have intersection, must be Kinematics of double semileptonic decay Back-to-back correlation of the two B constrains their direction to the intersection of the 2 cones. Exclusive B→X u l or Signal side reconstruction

2004/8/17ICHEP The ratio N obs /N expected = 0.89 ±0.08 is used to correct the MC efficiency for  l and  l detection. Calibration with B sig →D*l Decays Validity of the method for double semileptonic decay detection has been tested with M(K +  -  - ) on the signal side x 2 distribution N obs =147±12 The method works ! Dots: Data Histo: MC Exclusive B→X u l ( N expected =165) M(K  ) GeV/c 2 x2x2

2004/8/17ICHEP Signal Extraction We extract  l /  l signals simultaneously by fitting 2D (m X, x 2 ) distribution. Fitting components:  l,  l, other X u l, BB background. PDF’s are based on MC. Constraint for extracted Br: Br(  l  +Br(  l  +Br(other X u l )=Br(X u l ) Exclusive B→X u l Fitting results for all q 2 data.  l  (82±13)  l  (65±20) other X u l BB x 2 dist. for  mass region (I) x 2 dist. for  mass region (II) I II m X GeV/c 2 x2x2 x2x2  l  decays are cleanly extracted ! 140fb -1

2004/8/17ICHEP Extraction of q 2 Distribution q 2 distribution is extracted by fitting the (m X,x 2 ) distribution for three q 2 intervals. Exclusive B→X u l △ UKQCD ○  Ball’01 □ ISGW II    l + △ UKQCD ○  Ball’01 □ ISGW II ◇ Melikhov’98    l + At the present accuracy, the obtained q 2 dist. does not exclude any tested models Extracted q 2 dist. FF-dep. 140fb -1 Preliminary q 2 <8GeV 2 q 2 :8-16GeV 2 q 2 >16GeV 2 m X dist. for three q 2 intervals m X (GeV/c 2 )

2004/8/17ICHEP |V ub | from B 0 →   l + |V ub | determined from B >16GeV 2 (B 0 →   l + ) with lattice QCD. Exclusive B→X u l w/ quenched LQCD [FNAL/JLQCD/APE/UKQCD] Average 4th error from FF-dep. in Br is small for  l data w/ unquenched LQCD [FNAL/HPQCD] Preliminary results reported at Lattice’04. FNAL’04 HPQCD 140fb-1, preliminary

2004/8/17ICHEP Summary We have obtained preliminary |V ub | results from Inclusive B→X u l w/ fully reconstructed tag. Results are compatible and consistent with the previous exp’s. Exclusive B→X u l (B 0 →  l ) 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 |V ub |

2004/8/17ICHEP Backup Slides

2004/8/17ICHEP Systematic Uncertainties b  u MC statistics = 4% model dep. = 4.2% 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 R e freco and R e lept % b  c MC statistics = 15% model dep. = 5% Variate inclusive parameters within errors Dl (  D =1.19±0.19) D*l (  A1 =1.51±0.13) D**l % % % Inclusive B→X u l

2004/8/17ICHEP Systematic Uncertainty Major contribution D * l calibration Statistics of detected D * l  8.3% Error of Br(B 0  D * l )4.3% BB background shape tested  B(  l ) (  B(  l )) in MC by removing charged track by 1% -4.2(+23.5) % removing    by   -1.1(+12.8) % Replacing K  with   by 2% -0.5(+16.6) % Exclusive B→X u l Significant change in  B(  l ), due to the broad width of  meseon.

2004/8/17ICHEP 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) B   Form-Factor from LQCD Include 15% quenching error ( given for q 2 >16GeV 2 ) Exclusive B→X u l

2004/8/17ICHEP 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% Error of FF from Unquenched LQCD Number given by M.Okamoto (FNAL) and J.Shigemitsu (HPQCD) in private communications. Exclusive B→X u l