IFAE 2003 Lecce. Alessio Sarti University and INFN Ferrara. BaBar CLEO. Motivation. Inclusive V ub Exclusive V ub Summary, Outlook and Conclusions

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1 Measuring V B-factoriesB BaBar Motivation CLEO Inclusive V ub Exclusive V ub Summary, Outlook and Conclusions IFAE 2003 Lecce Belle Alessio Sarti University and INFN Ferrara

2 Motivation Measurements of V ub and V cb provide stringent consistency tests of the unitarity triangle (UT) _ η sin2β -1 V ub V cb 0 γ β V ub = Aλ 3 (ρ 2 +η 2 ) ½ e -iγ 1 _ ρ V ub error will soon limit UT tests, Need to measure V ub to better than 10% σ(sin2β)» 0.02 expected in 2007 IFAE 2003 A. Sarti 2

3 Kinematic Variables B(B X c lν)» 50 B(B X u lν) m X 2 f u ~ 70% E X E l f u ~ 10% q 2 f u ~ 25% Vary m b ± 150 MeV and λ GeV 2 Generator Fazio, Neubert, JHEP 9906, 017 (1999) Limits for B -> X c lν IFAE 2003 A. Sarti 3

4 V ub inclusive measurements IFAE 2003 A. Sarti 4

5 Lepton Endpoint (CLEO-BaBar BaBar) CLEO: A Bornheim et al, PRL 88, (2002) BaBar: B Aubert et al, hep-ex/ CLEO BaBar Preliminary ICHEP02 Data sample Cont. supp. p* range Sys error leading cont. 9.1(on) 4.3(off) neural net (GeV/c) B X c lν bkg 20.6(on) 2.6(off) R 2 < (GeV/c) efficiency and continuum bkg Radiative corr 5% 11% partial BR 0.230±0.015 ± ±0.014 ±0.014 f u ( p) (b sγ) 0.130±0.024 ± ±0.014 ±0.009 Subl. corr Subleading terms in shape fnct f u Luke, Mannel, Leibovich, Ligeti, Neubert IFAE 2003 A. Sarti 5

6 Lepton Endpoint Results V ub = From branching ratio to V ub B( b ul ( ν ) 1.55ps ) τ B (1.0 ± pert m b ± 90 MeV ± /m Uraltsev, Hoang, Ligeti, CKM b ) V ub V ub CLEO result = (4.08± 0.34(exp) ± 0.44(f 0.16(theo) 0.24( s )) 10 3 u ) ± ± b γ BaBar result (Preliminary ICHEP02) = (4.43± 0.29(exp) ± 0.50(f 0.25(theo) 0.35( s )) 10 3 u ) ± ± b γ (expect new BaBar result with 82 fb -1 data sample in summer) IFAE 2003 A. Sarti 6

7 Hadronic Recoil Mass (m( X ) p(l) D* n Tag side additional n (BELLE) B tag P m X = n (BELLE) Nch Y(4S) i= 1 P ch i + N γ j= 1 B recoil P γ j Recoil side n X u l p l > 1.0 GeV/c energy substituted mass D* p(l) B missing mass squared Xu n l B Subtract combinatorial bkg Y(4s) Btag (recoil) kinematics know with small uncertainties Btag (recoil) flavor Btag (recoil) charge (B 0 - B + separation) m X reconstruction Y(4s) Lepton charge Btag (recoil) flavor correlation Kinematic constraints to improve m X resolution Partially reconstructed missing mass (soft p) IFAE 2003 A. Sarti 7

8 Analysis Method (BaBar( BaBar, BELLE) Analysis of semileptonic B meson M miss2 < 0.5 GeV 2 Enrich signal region BaBar veto on K ± or K S use depleted region as control sample Reduce systematics measure ratio R u = B (B X u l ν) / B (B X l ν ) BELLE m X < 1.55 GeV reconstructed m X [GeV] reconstructed m X [GeV] m ν2 = m B 2 + m Dl 2-2(E B E Dl -2 p B p Dl 4cosθ BDl ); p B on cone, azimuthal angle unknown 2 neutrinos, p B on crossline of 2 cones p B = (x,y,z) solutions have x 2 > 0 (cut > -0.2) IFAE 2003 A. Sarti 8

9 V ub BaBar & Belle V ub (m X ) Signal region: M X < 1.55 GeV Data Sample: 82 fb -1 on 167 ± 21 events S/B ~1.7 = (4.52± 0.31(stat) ± 0.27(sys) ± 0.40( b u, c) ± 0.26(theo)) 10 3 Main contribution to sys error comes from Fermi motion parametrization Theo error comes from conversion of BR result into V ub sig bkg Data Sample: 78 fb -1 on 8.8 fb -1 off-peak V ub = (5.00± 0.60(stat) ± 0.23(sys) ± 0.39( b u, c) ± 0.36(theo)) 10 3 Signal region M X < 1.5 GeV 172 ± 28 events IFAE 2003 A. Sarti 9

10 Belle & CLEO V ub with n reco Annealing analysis: S Kirkpatrick et al, Science 220, 4598 (1983) divide event into 2 Bs, combinatorial minimize W = PDF (random)/ {PDF(correct) +PDF(random)} Signal region: q 2 > 7 W GeV 2, M X < 1.5 GeV Belle M 2 miss average efficiency ~0.3%, corrected with control sample Belle Moriond 2003 M X [GeV] q 2 > 7 GeV 2 Signal: 1148 events, S/B 0.27 m X ν reconstruction: A Bornheim et al hep-ex/ uses p miss and E miss, require m miss 2 = 0, set p ν = -p miss pioneered for exclusive V ub and D s -> µν CLEO Fit to kinematic variables q 2, M X and cosθ Wl q 2 > 10 GeV 2, m X < 1.5 GeV IFAE 2003 A. Sarti 10

11 V ub inclusive summary Moriond 2003 V ub inclusive measurements very active field many new results since last year improved precision Value Stat det b c b u f u sh fct theo Bfactory average Bfactory V ub = (4.32 ± 0.57) x 10-3 Averaging (F. Muheim) stat & det error uncorrelated rescale theo error add 5% for shape function IFAE 2003 A. Sarti 11

12 V ub exclusive measurements IFAE 2003 A. Sarti 12

13 Measurements general features BaBar 01 (SLAC-PUB-9618) ρ + lν,ρ 0 lν,ϖlν BELLE 02 (Y.Kwon,ICHEP) ρ+lν,ρ0lν; 03 ϖlν CLEO 03 (CLNS 03/1819) π +/0 lν, ρ +/0 lν,ϖlν,ηlν; 00 ρ +/0 lν,ϖlν Full reconstruction of event (ν reconstruction): CLEO: tuned BaBar-BELLE: standard set of cuts B reco cuts: E,p E (CLEO,BaBar, BELLE) m ES cut (CLEO, BELLE) cosθ BY (CLEO, BaBar,BELLE) Fit mππ (mlν) p miss p ν (GeV/c) N lep =1, charge conservation (CLEO,BELLE) ν reconstruction cuts (CLEO,BELLE) IFAE 2003 A. Sarti 13

14 BaBar & CLEO analysis ρlν BaBar 02 Fit m ππ, E, p l High eff & high bkg Sensitive for p l >2.3GeV/c ρlν CLEO 03 Fit mlν, E, (m ππ,m πππ in ρ,ϖ) Rates obtained in 3 q 2 intervals (no p l in fit) : minimize signal and detector modeling dependence Use p l >1.0GeV/c (pseudo.) and p l >1.5GeV/c(vector) IFAE 2003 A. Sarti 14

15 BELLE analysis Fit E vs p l (π), E vs m ππ (ρ ), p l vs m ππ (ϖ) πlν: unfold dγ/dq 2 after global fit ϖlν: primarily sensitive for p l >2.4 GeV/c BELLE 03 ϖlν BELLE 02 IFAE 2003 A. Sarti 15

16 Systematics K L energy deposit Tracking eff Simulation of splitoff Physics models Common GEANT base (correlation for averages) MC modeling issues Signal modeling: need to evaluate FF for π,ρ,ϖ separately Generic X u lν bkg: Hadronization models? Eval of non-resonant ππlν CLEO 03 Variation (%) π - l + ϖ ρ - l + ν γ eff γ resol K L showering Particle ID Splitoff rejection Track eff Track resolution Splitoff simul K L prod ν prod Total ηlν IFAE 2003 A. Sarti 16

17 Rate model dependence q 2 biases introduce model dependence: efficiency, p l > p min Continuum rejection (low q 2 kin var ~ jetty) Cross-feed bkg rates (high at low q 2 ) dγ/dq 2 : low FF dependence BELLE: unfold q 2 after global fit IFAE 2003 A. Sarti 17

18 V ub results (exclusive) 3.23 ± ± 3.64 ± 0.22 ± ± 0.13 ± 0.24 ± ± 0.20 ± 0.28 Need to understand how to average results from different models 3.24 ± 0.22 ± 0.13 ± ± ± ± ± IFAE 2003 A. Sarti 18

19 Conclusions V ub with inclusive B X u lν decays Large theoretical progress over last decade (HQET & OPE) best measurement at 14% precision with similar experimental and theoretical errors neutrino reconstruction is crucial for q 2 measurements of Λbar and λ 1 and sh. function from B X c lν and B -> X s γ Try to measure m b to constrain theo error 2007 aim for V ub error smaller than 10% V ub with exclusive B X u lν decays Better FF normalization is needed to extract V ub Study dγ/dq 2 : test on FF dependece Exclusive and inclusive results consistency? B factories opened up new experimental methods: hadronic recoil mass spectrum with fully reconstructed recoil B meson tag IFAE 2003 A. Sarti 19