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Inclusive semileptonic B decays: experimental

Inclusive semileptonic B decays: experimental. Elisabetta Barberio University of Melbourne FPCP: Vancouver April 2006. Standard Model Consistency Tests. V ub and V cb provide a test of CP violation in the Standard Model comparing the measurements on the ( r , h ) plane.

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Inclusive semileptonic B decays: experimental

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

  2. 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| E. Barberio

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

  4. Inclusive semileptonic decays Many theorists love inclusive semileptonic decays Short distance is calculable Long distance leading orderand 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 E. Barberio

  5. 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 E. Barberio

  6. Vcb from inclusive semileptonic decays exp. D|Vcb|<1% Gsldescribed 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/mb3terms and above E. Barberio

  7. 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/mb3terms  reduce theory error on Vcb and HQ parameters E. Barberio

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

  9. moments in semileptonic decays E : lepton energy spectrum in BXc n (BaBar BelleCLEODelphi) MX 2: hadronic mass spectrum in BXc n (BaBarCDFCLEODelphi) 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 E. Barberio

  10. Parameters Extraction BABAR: up to 1/mb3:fit ~90 measurement to extract HQ parameter and Vcb at the same time o= used,•= unusedin the nominal fit BABAR MX moments M1x M2x M4x M3x c2/ndf =20/15 M2l M3l M1l M0l P.Gambino, N.Uraltsev hep-ph/0401063 hep-ph/0403166 Red line: HQE fitYellow band: theory errors E. Barberio

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

  12. Vub inclusive determination B Xuln rate tree level from OPE  corrected forperturbativeas andnon-perturbative1/mb terms In principle main uncertainty from mb5 BUT….. Br(BXuln)/Br(BXcln) =1/50 E. Barberio

  13. Shape Function F(K+) L = MB -mb K+ 0 Limited phase space to reduce the B  Xcln background: OPE doesn’t work everywhere in the phase space  non-perturbativeShape Function F(K+) to extrapolate to the full phase space 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 E. Barberio

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

  15. Lepton Endpoint BABARPRD 73:12006Belle PLB 621:28CLEO PRL 88:231803 BaBar First measurement from CLEO El>2.3 GeV BaBar El>2.0 GeV Belle El> 1.9 GeV Crucial accurate subtraction of background is crucial! S/B ~1/10 eff~ 40% E. Barberio

  16. Measuring mXq2 P+ BABARhep-ex/0507017Belle 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% E. Barberio

  17. Measuring Partial Branching Fraction P+ BLNP PRL93:221802 E. Barberio

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

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

  20. 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% E. Barberio

  21. Theory Errors l b B u q n q Quark-hadron duality is not considered (cut dependent) • b clnand 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 E. Barberio

  22. 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 fractionmb(MS)=4.200.04 GeV as  1.0% on event fraction total GSL  3.0 % E. Barberio

  23. 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 E. Barberio

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

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

  26. Conclusions b cln Vcb2% 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 E. Barberio

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

  28. Mx unfolded spectrum for BXcln Belle D* D D** E. Barberio

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

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