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Status and perspectives of measurements of V ub and g

Status and perspectives of measurements of V ub and g. Gianluca Cavoto INFN and Universit à Roma ‘La Sapienza’ BaBar Collaboration LHC Flavour Workshop CERN – 7-10 nov 2005. The reference Unitarity Triangle. L.Silvestrini, LP’05. g and V ub from pure tree level processes!

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Status and perspectives of measurements of V ub and g

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  1. Status and perspectives of measurements of Vub and g Gianluca Cavoto INFN and Università Roma ‘La Sapienza’ BaBar Collaboration LHC Flavour Workshop CERN – 7-10 nov 2005 G.Cavoto

  2. The reference Unitarity Triangle L.Silvestrini, LP’05 • g and Vub from pure tree level processes! • Assumptions: • 3 generations only • No new physics at tree level • Any new physics must satisfy this constraint Mainly results from BaBar (Summer 2005) G.Cavoto

  3. 1: 2: 1: Vub, inclusive and exclusive • Inclusive • large signal rate, large Xcl background • Select limited region of phase space • Total rate evaluates from OPE • Non-perturbative contribution: Shape Function • determined experimentally from bsg, bcl BNLP S.W. Bosch, B.O. Lange, M. Neubert, G. Paz, Nucl. Phys. B 669, 355 (2004) B.O. Lange, M. Neubert, G. Paz, hep-ph/0504071 BLLC.W. Bauer, Z. Ligeti, M. Luke, hep-ph/0111387 Form Factor • Exclusive • Low signal rate, background rejection (kin. constraint) • FormFactors normalization (Vub) : theory error FF shape (acceptance) affects exp’l uncert. G.Cavoto

  4. Measuring Vub, experimental methods • Tagging methods G.Cavoto

  5. Vub: inclusive analyses Endpoint spectrum 2.0 < Ee < 2.6 GeV +0.42 – 0.38SF |Vub| = (4.44 ± 0.25exp±0.22th-BLNP) x 10-3 s ~ 12% b →sg, b →clv moments (BaBar) [O.Buchmuller and H.Flacher, hep-ph/0507253 ] MX vs q2: hadronic tag Neutrino reconst.: El vs q2 b→clnand other bkg signal region signal region sideband region signal b→uln non-signal b→uln q2 cut |Vub|BLL= (4.82 ±0.26stat ± 0.25syst±0.46SF+theo) x 10-3 s ~ 12% +0.46 – 0.36 SF s ~ 13% |Vub|BLNP(BaBar b→cln)= (4.65 ±0.24stat ± 0.24syst ±0.23th) x 10-3 G.Cavoto 211 fb-1 hep-ex/0507017

  6. HFAG results are rescaled to common HQE inputs: mb=4.60±0.04 GeV, μπ2=0.20±0.04 GeV2 Results (and current limitations) Eℓ endpoint • Limited by uncertainties on SF paramaters (mb) • Improve inputs from bcln and b sg • Improve SF evaluation • Weak annihilation • Should be small (2%) • Can be checked with B0/B+comparison Eℓvs. q2 mX mXvs. q2 expt mb, theory G.Cavoto

  7. Vub: exclusive, Bpln,rln Binning in q2 Untagged Semileptonic tag No phase space cut Coarse q2 binning Hadronic tag Low background, no phase space cut!!! Low signal rate More channels in progress: G.Cavoto

  8. Vub: exclusive results Full q2 range FNAL LQCD Projection to 1 ab-1 (data taken to be on BK fit curve from present measurement). In the high q2 region alone, branching fraction at (6-7)% , or (3-3.5)% on |Vub |. Lattice expect to reach 6% G.Cavoto

  9. MX spectrum Vub: outlook 250 fb-1500 fb-1 Projection to 1 ab-1 Inclusive Combination of larger dataset and confidence in theory (subleading SF ): 5-7% Exclusive Need help from theory: Uncertainty on |Vub| dominated by theory error! (~15%) • Reliable error estimate for rln FF needed forpandrBF and |Vub| • Progress in LQCDforpln : theory error 6-7% ? (Lubicz, Lattice04; Bernard CKMWS 05) Big improvements possible total error ~ 9% G.Cavoto

  10. Interference when D final state common to both D0 and D0 g from direct CP violation Relative size (rB) of B decay amplitudes Larger rB, larger interference, betterg experimental precision (degrees) 0.1 0.2 G.Cavoto

  11. Gronau & London, PLB 253, 483 (1991), Gronau & Wyler, PLB 265, 172 (1991)]. Gronau London Wyler method Theoretically clean, but with 8-fold ambiguity D decays into CP eigenstate • CP modes: small D0 branching ratio Select CP-even and CP-odd final states 3 observables, 3 unknowns Experimentally • Normalize to D0decay into flavour state (K-p+) G.Cavoto

  12. PRD71,031102(2005) ACP RCP Systematic uncertainties hardly visible ! DCP+ DCP- GLW results ! Large value (rB)²(D0K-)= -0.17±0.16 (rsB)²(D0K*-)= 0.30±0.25 G.Cavoto

  13. Atwood, Dunietz, & Soni, PRL 78, 3257 (1997), PRD 63, 036005 (2001) Atwood Dunietz Soni method D decay into flavor state dB dD Count B candidates with opposite sign kaons Input: Phys.Rev.Lett.91:171801,2003 D decay strong phase dDunknown G.Cavoto

  14. 0<dD<2p rD±1s 51°<g<66° * g[0,p] * rB<0.23 @ 90% CL * Bondar & Gershon PRD70,091503(2004) • D*0→D0p0/D0g ≠ indD*by p (r*B)²< (0.16)²@ 90% CL (Bayesian r*B²>0 & uniform,  g and dD*) * hep-ex/0504047 232×106BB ADS: results B-→D0K- B-→D*0[D0p0]K- No DCS signal … B-→D*0[D0g]K- G.Cavoto

  15. Giri, Grossman, Soffer, & Zupan, PRD 68, 054018 (2003), Bondar (Belle), PRD 70, 072003 (2004) If we knew the charm phase shift dD? B-D(*)0K- D0(KSpp) Dalitz analysis Amplitude for B-/B+ “D0”K-/K+ g=75,d=180,rB=0.125 Sensitivity to g Isobar model for f(m2+ ,m2- ) can fix phase variationdD across Dalitz plot. Only two-fold ambiguity in g extraction r(770) DCS K*(892) G.Cavoto

  16. Determined on D* D0p sample D0(KSp+p-) Dalitz model D0 decay modelcoherent sum of Breit-Wigner (BW) amplitudes(quasi 2 body terms). CA K*(892) 13distinct resonances (3 WS DCS) +1 NR term. This isobar model is not so good for pp S waves need controversials(500) / s’(1000) to describe reasonably well the data. Plot of mpipi r(770) Better description of quasi 2-body terms: BW +pp S-waveswith K-matrix formalism Anisovich & Saratev Eur. Phys. J A16, 229 (2003) DCS K*(892) No D-mixing, No CP violation in D decays G.Cavoto

  17. 2D 2 s CL 1 s CL (stat. only) g from Dalitz ~ ~ y*± y± D0K- D*0K- B- B+ B- d  2rB|sing|≠0 sizeof direct CPV d B+ d* x*± x± g=[67°±28°(stat.) ±13°(syst. exp.) ± 11°(Dalitz model*) ] *evaluated removing pp S-wave 3°for K-matrix / BW difference G.Cavoto

  18. Projected g uncertainty Model independent approach A.Bondar and A.Poluetkov, hep-ph/0510246 rb =0.2 rb =0.1 Projected sys error due to D0 Dalitz plot Charm and (super)B-factory interplay G.Cavoto

  19. Summary 2005 • Many different and independent techniques to constrain Vub and g • By 2008 1 ab-1/B-factory • Vub inclusive: 5-6% • Vub exclusive : dominated bytheoretical error total error 8% (?) • g • Dalitz technique most promising • rb critical parameter for sensitivity • Dalitz model limit at 5° ? • More stat for model indep. • Including more modes/techniques addsto 1/N improvements 2008 G.Cavoto

  20. Backup slides G.Cavoto

  21. UT in 2008 2005 2008 G.Cavoto

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