Inclusive semileptonic B decays: experimental Elisabetta Barberio University of Melbourne FPCP: Vancouver April 2006

Standard Model Consistency Tests Vub and Vcb provide a test of CP violation in the Standard Model comparing the measurements on the (r, h) plane The width of the green ring need to be reduced to match sin2b and other measurements The error on the ring width is dominated by Vub Goal: Accurate determination of |Vub| April 2006 E. Barberio

Semileptonic B decays Vcb ,Vub tree level, short distance: decay properties depend directly on |Vcb|, |Vub|,mb perturbative regime (asn) Vcb ,Vub u + long distance: ,u But quarks are bound by soft gluons: non-perturbative (LQCD) long distance interactions of b quark with light quark April 2006 E. Barberio

Inclusive semileptonic decays Many theorists love inclusive semileptonic decays Short distance is calculable Long distance leading order and short distance contribution are cleanly separated and probability to hadronnize is 1 To compare Operator Product Expansion predictions with experiments: integration over neutrino and lepton phase space provides smearing over the invariant hadronic mass of the final state April 2006 E. Barberio

Inclusive semileptonic decays Vcb vs Vub Vcb: most accurate determination from the inclusive decays 2% precision limited by theory error precise Heavy Quarks parameters, tests of OPE Vub: 7.5% precision shared between experimental and theoretical errors small rate and large bcln background space cuts to remove bcln background which introduce O(1) dependence on non-preturbative b-quark distribution function April 2006 E. Barberio

Vcb from inclusive semileptonic decays exp. D|Vcb|<1% Gsl described by Heavy Quark Expansion in (1/mb)n and ask non perturbative parameters need to be measured The expansion depend on mb definition: non-perturbative terms are expansion dependent Theory error was dominated by 1/mb3 terms and above April 2006 E. Barberio

Bc moments in semileptonic decays Xn are relate to non-perturbative parameters moments evaluated on the full lepton spectrum or part of it: p > pmin in the B rest frame higher moments are sensitive to 1/mb3 terms  reduce theory error on Vcb and HQ parameters April 2006 E. Barberio

Inclusive SL decays rate shape |Vcb| mc, m2G, mb, m2p Difficulty to go from measured shape to true shape: e.g. QED corrections, accessible phase space, resolution, background April 2006 E. Barberio

moments in semileptonic decays E : lepton energy spectrum in BXc n (BaBar Belle CLEO Delphi) MX 2: hadronic mass spectrum in BXc n (BaBar CDF CLEO Delphi) Most recent measurements from Belle mx (GeV) P*l (GeV) P*l (GeV) Plmin =0.7 GeV Plmin =0.4 GeV from the moments of these distributions we get Vcb and HQ parameters April 2006 E. Barberio

Parameters Extraction BABAR: up to 1/mb3: fit ~90 measurement to extract HQ parameter and Vcb at the same time MX moments o= used, •= unused in the nominal fit BABAR c 2/ndf =20/15 M1x M2x M3x M4x M0l M1l M2l M3l Red line: HQE fit Yellow band: theory errors P.Gambino, N.Uraltsev hep-ph/0401063 hep-ph/0403166 April 2006 E. Barberio

Vcb and HQ parameters Global fit Kinetic scheme expansion (hep-ph/0507253) dVcb @ 2% mb < 1%, mc @ 5% U(1S) expansion scheme has similar results Exp HQ Gsl used measurements: April 2006 E. Barberio

Vub inclusive determination B Xuln rate tree level from OPE  corrected for perturbative as and non-perturbative 1/mb terms In principle main uncertainty from mb5 Tree-level rate was calculated at the quark level, but what we observe is the hardrons. BUT….. Br(BXuln)/Br(BXcln) =1/50 April 2006 E. Barberio

Shape Function Limited phase space to reduce the B  Xcln background: OPE doesn’t work everywhere in the phase space  non-perturbative Shape Function F(K+) to extrapolate to the full phase space F(K+) L = MB -mb K+ Detailed shape not constrained, in particular the low tail Mean and r.m.s. are known Shape Function need to be determined from experimental data April 2006 E. Barberio

Inclusive B  Xuln mu << mc  exploits different kinematics l q2 = lepton-neutrino mass squared mX = hadron system mass El = lepton energy P+ = EX -|PX| Signal events have smaller MX and P+  Larger El and q2 bu bc Not to scale! April 2006 E. Barberio

Lepton Endpoint First measurement from CLEO El>2.3 GeV BABAR PRD 73:12006 Belle PLB 621:28 CLEO PRL 88:231803 First measurement from CLEO El>2.3 GeV BaBar BaBar El>2.0 GeV Belle El> 1.9 GeV Crucial accurate subtraction of background is crucial! S/B ~1/10 eff~ 40% DB (10-4) BABAR 80fb-1 5.72 ± 0.41stat ± 0.65sys Belle 27fb-1 8.47 ± 0.37stat ± 1.53sys CLEO 9fb-1 2.30 ± 0.15stat ± 0.35sys April 2006 E. Barberio

Measuring mX q2 P+ BABAR hep-ex/0507017 Belle PRL 95:241801 Reconstruct all decay products to measure MX ,q2 or P+ fully-reconstructed B meson flavor and momentum known lepton in the recoil-B mmiss consistent with a neutrino lepton charge consistent with B flavor left-over particles belong to X equal mB on both sides; mmiss = 0 S/B ~ 2 Eff~ 0.1% April 2006 E. Barberio

Measuring Partial Branching Fraction P+ BLNP PRL93:221802 DB (10-4) BABAR 211fb-1 mX < 1.7, q2 > 8 8.7 ± 0.9stat ± 0.9sys Belle 253fb-1 first measurement of P+ spectrum mX < 1.7 12.4 ± 1.1stat ± 1.0sys 8.4 ± 0.8stat ± 1.0sys P+ < 0.66 11.0 ± 1.0stat ± 1.6sys April 2006 E. Barberio

|Vub| Turning DB into |Vub| Eg mb mX El HQE Fit El q2 mX b → sg Shape Function Eg mb Inclusive b → clv mX El HQE Fit SSFs Inclusive b → ulv El HFAG main results: HQ parameters form b  Xcln and b  Xsg hep-ph/0507253 |Vub| q2 mX duality WA

Dealing with Shape Function easy to fit shape function Better resolution  K* peak (more difficult for SF) Belle Eg>1.8 GeV E*g (GeV) Eg (GeV) Solution  use directly the g spectrum: theory April 2006 E. Barberio

Inclusive |Vub|: BLNP framework |Vub| world average as of Winter 06 Inputs: mb(SF) = 4.60  0.04 GeV mp2(SF) = 0.20  0.04 GeV2 |Vub|BLNP=(4.45  0.20  0.26) 10-3 d|Vub| =  7.3% Statistical 2.2% Expt. syst. 2.7% B  Xcln model 1.9% B  Xuln model 2.1% Subleading SF 3.8% other theory error 4.5% April 2006 E. Barberio

Theory Errors Quark-hadron duality is not considered (cut dependent) b cln and b  sg data fit well HQ predictions Weak annihilation   1.9% error Expected to be <2% of the total rate Gw.a./G(b  u) < 7.4 % from CLEO HQ parameters   4.1% mainly mb; kinematics cuts depend on mb,! Sub-leading shape function   3.8% dominated by the lepton endpoint measurements B u b l n q April 2006 E. Barberio

Inclusive |Vub|: DGE framework Dressed Gluon Exponentiation (DGE) on-shell b-quark calculation converted into hadronic variables used as approximation to the meson decay spectrum Still digesting the method |Vub|DGE = (4.41  0.20  0.20) 10-3 DGE theory  2.9% matching scheme method and scale mb(MS)   1.3% on event fraction mb(MS)=4.200.04 GeV as   1.0% on event fraction total GSL   3.0 % April 2006 E. Barberio

Vub without Shape Function Babar Based on Leibovich, Low, Rothstein, PLB 486:86 First proposal by Neubert Weight function Babar Babar mxcut OPE mx<2.50 GeV LLR mx<1.67 GeV April 2006 E. Barberio

|Vub|: inclusive vs exclusive W.A. Winter 06 |Vub| exclusive W.A. Winter 06 April 2006 E. Barberio

|Vub|: CKM consistency Most probable value of Vub from measurements of other CKM parameters Standard Model predictions with Dms measurement (thank to Pierini) Vub from exclusive measurements Vub from inclusive April 2006 E. Barberio

Conclusions b cln b uln Vcb 2% error dominated by theory, mb @1% (kinetic and U(1S) schemes), mc @5% (kinetic scheme) but how well do we know the B Xcln spectrum? b uln Vub ~7.4% error shared between theoretical and experimental inclusive vs exclusive less than 1.4 s difference, depending on the inclusive extracting method We have now different methods to extract Vub |Vub| @ 5% possible? Improve knowledge of B Xcln, B Xuln and more work on the theoretical error April 2006 E. Barberio

Inclusive |Vub|: comparisons HQ parameters from cln and sg HQ parameters from sg only April 2006 E. Barberio

Mx unfolded spectrum for B  Xc l n Belle April 2006 E. Barberio

photon energy spectrum Eg : photon energy spectrum in Bsg (BaBar Belle CLEO Delphi) u, c, t photon energy spectrum in B Xsg not sensitive to new physics and give information on B structure Belle Eg>1.8 GeV Eg>2 GeV CLEO April 2006 E. Barberio