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Semileptonic B decays, B mixing and magnitudes of CKM elements at B A B AR

Semileptonic B decays, B mixing and magnitudes of CKM elements at B A B AR. David Côté, Université de Montréal for the B A B AR collaboration. DAΦNE 2004: Physics at meson factories. ∫ L on dt = 82 fb -1. 88  10 6 BB.

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Semileptonic B decays, B mixing and magnitudes of CKM elements at B A B AR

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  1. Semileptonic B decays, B mixing and magnitudes of CKM elements at BABAR David Côté, Université de Montréal for the BABAR collaboration DAΦNE 2004: Physics at meson factories

  2. ∫ Lon dt = 82 fb-1 88106 BB Results presented today used less than half of the data we have now. Outline • |Vcb| • |Vub| • B0 – B0 mixing semileptonic B decays: BXcl  or BXul  md, ... David Côté, Université de Montréal

  3. Why studying semileptonic B decays and B0 - B0 mixing? • To (over-)constrain the Standard Model and determine some of its fundamental parameters: mb, mc and CKM matrix elements • To know more precisely parameters needed by other analyses (md, branching fractions, form factors,...) • To learn about QCD and effective QCD David Côté, Université de Montréal

  4. Problem: large uncertainties in mb, mc, ’s and ’s Solution: Measuring mb, mc, G, ,LS, D, simultaneously to Br(BXc e ) and |Vcb| using HQE’s predictions of El and MXcmoments. i=1..3 i=1..4 Inclusive |Vcb| measurement strategy • f , f0 : heavy quark expansion (HQE) formulae* • mb and mc : running quark masses (at  =1 GeV) • G, ,LS, D : non-perturbative QCD parameters *Gambino & Uraltsev hep-ph/0401063 hep-ph/0403166 David Côté, Université de Montréal

  5. esig e- Bsig Btag e+ etag esig energy spectrum used for moments measurement ν electron energy moments • Strategy: identify B  Xc e  decays with di-electron events • Require typical B-B event topology, one high momentum etag and one opposite charge esig • Subtract remaining backgrounds (mostly from data control samples) • Corrections applied for Bremsstrahlung, e ID efficiency, etc. Data sample: ∫ L dt = 47.4 fb-1 400,000 events! Accepted by Phys. Rev. D hep-ex/0403030 David Côté, Université de Montréal

  6. BABAR El* > 0.9 GeV p Breco e- D* Brecoil e+ l Xc Clear sign of higher charm resonances ν hadronic mass moments Accepted by Phys. Rev. D hep-ex/0403031 • Strategy: identify B  Xcl  decays on the recoil of fully reconstructed B’s • Semileptonic side requirements : • exactly one e or  with p* > 0.9 GeV/c • Emiss, Pmiss consistent with a neutrino and net event charge  1 • MXc reconstructed with a kinematic fit to all remaining particles • Corrections for small MXc reconstruction bias computed from Monte Carlo David Côté, Université de Montréal

  7. Excellent agreement between lepton and hadron moments! Fit results Accepted by Phys. Rev. Lett. hep-ex/0404017 MXc and El moments as a function of minimum El cut χ2 = 15 Ndof = 20 used in global fit not used in global fit • Excellent agreement between data and HQE predictions! David Côté, Université de Montréal

  8. |Vcb|: result and comparison • 2% error on |Vcb|! |Vcb| Br(BX l ) David Côté, Université de Montréal

  9. theory theory mb, mc: result and comparison kinetic mass scheme Conversion of mb and mc from kinetic mass to MS scheme by N. Uraltsev (hep-ph/9708372, hep-ph/0302262 , hep-ph/0304132) David Côté, Université de Montréal

  10. *Br(BXul ) extracted from Ru using ref Phys.Rev.D67:031101,2003 ∫ L dt = 82 fb-1 Several avenues currently considered in order to reduce further the theoretical uncertainties. Inclusive |Vub| Phys. Rev. Lett. 92:071802,2004 • Strategy: same B  Xl  selection as hadron mass moments (slide 6) • BXul  selection: kaon veto, low MX • Measurement of for systematic errors cancellation Monte Carlo David Côté, Université de Montréal

  11. ∫L dt = 50.5 fb-1 Exclusive |Vub| Phys. Rev. Lett. 90:181801,2003 • Strategy: untagged identification of B e  decays with “ reconstruction” • Signal extracted by requiring: • very high momentum electron • E = Ebeam - E - El - Emisscompatible with zero • M compatible with  mass • Rather high theoretical uncertainties (~15%) • Relatively high yield: 834  102 events (only electrons and 50.5 fb-1) exclusive analysis advantage MC GeV/c • Much more to be expected soon: • larger dataset • additional decay modes • reduced theoretical uncertainties • form factor(s) measurement • new recoil techniques David Côté, Université de Montréal

  12. “unmixed” “mixed” Results (23106 BB): (averaged 1,2,5) (3) « classic » B0 - B0 mixing (1) Phys.Rev.Lett.88:221802,2002 (2) Phys.Rev.Lett.88:221803,2002 (3) Phys.Rev.Lett.89:011802,2002 (4) Phys.Rev.D66:032003,2002 (5) Phys.Rev.D67:072002,2003 • The B0 – B0 mixing technique is well-known and well-documented: • Determination of vertex and flavor of the two B’s • “t” between the two B’s estimated from distance between vertices David Côté, Université de Montréal

  13. d/d : lifetime difference between BH and BL mass eigenstates (not “Bshort” and “Blong”) z  (0,0): imply CPT violation |q/p|  1: imply ACP (ACP) is the amplitude for B0fCP (B0fCP) (): difference between flavor (mass) eigenstates Generalized B0 - B0 mixing analysis • B0 – B0 total decay-rate difference, CP violation in mixing and CPT violation were always neglected in mixing and CP measurements • The validity of these assumptions was recently confirmed in a generalized B0 - B0 mixing analysis using 82 fb-1 Phys.Rev.Lett.92:181801,2004 hep-ex/0403002,submitted to PRD David Côté, Université de Montréal

  14. Summary • New BaBar precision measurement of |Vcb|, Br(BXcl ), mb, mc and 4 HQE parameters. • 13% (18%) inclusive (exclusive) |Vub| measurement at BaBar using BXul  decays (currently dominated by theory errors, but much progress to be expected soon). • New measurement of d/d, |q/p| and z generalized mixing parameters validate the assumptions used for previous BaBar’s mixing and CP measurements. David Côté, Université de Montréal

  15. backup slides

  16. - plane David Côté, Université de Montréal

  17. md,s vs Vtd,s  [known factors] needs latttice QCD calculations  [known factors] also needs latttice QCD calculations, but easier to compute. David Côté, Université de Montréal

  18. electron energy moments Defining: We measured... • the first moment: • the central moments: n = 2,3 • the partial branching fraction (0th moment): David Côté, Université de Montréal

  19. HQE parameters We use calculations in kinetic mass scheme by Gambino and Uraltsev • (HQE to order 1/mb3, as2 ) • μπ2 - exp. value of kinetic energy of b quark inside B meson • μG2 - exp. value of chromomagnetic moment operator • ρD3 - exp. value of Darwin operator • ρLS3 – exp. value of Spin-Orbit operator hep-ph/0401063 hep-ph/0403166 Ơ(1/mb2){ Ơ(1/mb3){ David Côté, Université de Montréal

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