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Status and future perspectives on V cs and V cd

This talk focuses on the unitary test on the second row and measurements of Vcs and Vcd using experimental methods and theoretical tools like Lattice QCD and QCD Sum Rules.

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Status and future perspectives on V cs and V cd

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  1. Status and future perspectives on Vcs and Vcd Marina Artuso Syracuse University Marina Artuso WG1 CKM 2006

  2. Motivation: unitarity constraints    weak VCKM mass Wolfenstein eigenstates eigenstates parameterization To l3 in real part & l5 in im. part • CKM unitary  described by 4 parameters (3 real, 1 imaginary: e.g. A,l,r,h), but each quark mixing is in principle measurable  highly constrained system • This talk focuses on unitary test on the second row Marina Artuso WG1 CKM 2006

  3. Received a lot of attention in recent years because of developments in lattice QCD (see R. Van de Water presentation) Pseudoscalar hadronic final states preferred because they are stable to strong decay  e+ W+ Vcs and Vcd from charm semileptonic decays In D rest frame Squared 4-momentum transfer Vcq K,p D • We measure: Theory input Marina Artuso WG1 CKM 2006

  4. Two approaches • Assuming Vcs and Vcd known (Stone’s talk) • DK(K*)ln , Dpln determine form factor shapes & distinguish among models + test lattice QCD predictions (see S. Stone talk, WG2/3 joint session) • Note that lattice checks comparing semileptonic ff & fD can be done independently of knowledge of CKM parameters • Assuming lattice predictions OK (this talk) • measurements of Vcd & Vcs Marina Artuso WG1 CKM 2006

  5. Experimental methods • DD production at threshold: used by Mark III, and more recently by CLEO-c and BES-II. • Unique event properties • Only DD not DDx produced • Large cross sections: s(DoDo) = 3.720.09 nb s(D+D-) = 2.820.09 nb • Ease of B measurements using "double tags“ • B-factories (e+e-) + fixed target & collider experiments at hadron machines • D displaced vertex • D*+ p+D0 tag World Ave Continuum ~14.5 nb p K (ps) D0 e+ e- Marina Artuso WG1 CKM 2006

  6. Theoretical Tools • Lattice QCD • Theory (unquenched QCD), still has moderate systematic errors; however theoretical accuracy can be improved in a controlled fashion. • QCD Sum Rules • Equating phenomenological and theoretical spectral functions; • Determination of theoretical spectral functions by calculating two or three-point correlators in perturbative QCD, including corrections from the OPE Many parameters, difficult to improve their accuracy in a systematic fashion. • Phenomenological models • Important contributions to our understanding of charm decays • No way to improve these predictions in any systematic way Marina Artuso WG1 CKM 2006

  7. Lattice results for DK(p) e ne semileptonic decays • two form factors are needed to describe the vector current matrix element <P|Vm|D> : f+(q2) and f0(q2), (only f+(q2) needed if ml negligible) • Lattice QCD calculates both f+ and f0, since they can be fit simultaneously imposing the constraint f+(0)= f0(0) • Fermilab-MILC-HPQCD reported results using 2+1 flavors of improved staggered quark to implement non-quenched f.f. calculation • Dominant systematic error from heavy quark discretization (7% of the overall 10% uncertainty) Marina Artuso WG1 CKM 2006

  8. A snapshot of theoretical predictions • Other predictions are available from quenched lattice QCD calculations, QCD sum rules and form factor models Marina Artuso WG1 CKM 2006

  9. K- K+ - e+ CLEO-c results – tagged analysis 281 pb-1310K D+ 160K D0 Signal events: U = Emiss– |Pmiss| = 0 Tag allows to determine signal D0 momentum Signal semileptonic decay Marina Artuso WG1 CKM 2006

  10. CLEO-c results untagged analysis • Unspecified other side D decay, collect other showers and tracks • Use neutrino reconstruction like Bp/rln • Higher statistical accuracy, worse systematic error • Samples overlap Marina Artuso WG1 CKM 2006

  11. D K, pen Branching Fractions D → K e+ ν D → π e+ ν FNAL-MILC-HPQCD FNAL-MILC-HPQCD preliminary preliminary preliminary preliminary FNAL-MILC-HPQCD precision lags experiment. Marina Artuso WG1 CKM 2006

  12. Hill & Becher, Phys. Lett. B 633, 61 (2006) Form-Factor Parameterizations • In general • Modified Pole • Series Expansion Marina Artuso WG1 CKM 2006

  13. Form factor data and FNAL-MILC-HPQCD predictions CLEO-c preliminary-tagged • FNAL-MILC-HPQCD calculation uses modified pole model to fit for form factor from “measured”points [PRL 94, 011601 (2005)] • FF predictions: • DKen f+(0)=0.73±0.03±0.07 • a=0.50±0.04±0.07 • Dpen f+(0)=0.64±0.03±0.06 • a=0.44±0.04±0.07 Fnal-MILC-HPQCD Fnal-MILC-HPQCD Marina Artuso WG1 CKM 2006

  14. BELLE: PRL 97, 061804 (2006) [hep-ex/0604049]BaBar: hep-ex/0607077FOCUS: PLB607, 233 (2005) [hep-ex/0410037] Belle,BaBar,FOCUS D  K,pℓn form factorsdata Belle, 282fb-1, fully reconstructed events, excellent q2 resolution Aubin et al., PRL94, 011601 (2005)Abada et al., NuclPhys B619, 565 (2001) Unquenched LQCDQuenched LQCDSimple pole model Belle + FOCUS published Kℓn ~2.5k signal events Kℓn Belle FOCUS: ~13k events 75fb-1 FNAL MILC HPQCD: Aubin et al., PRL94, 011601(2005) pℓn 232 signal events q2 (GeV2) Marina Artuso WG1 CKM 2006

  15. Belle . . Belle Summary of lattice-experiment comparison D0 K-e+ne Assuming Vcs=0.9745 D0 p-e+ne Assuming Vcd=0.2238 FNAL.MILC-HPQCD FNAL.MILC-HPQCD Marina Artuso WG1 CKM 2006

  16. Using semileptonic width and form factors • Using the preliminary CLEO-c semileptonic widths G(DKene) =(8.70.16) x10-2 ps-1 and G(Dpene)= (0.76 0.03)x10-2 ps-1 and FNAL-MILC-HRQCD G(DKene)/|Vcs|2 and G(Dpene)/|Vcd|2 • Vcs=0.966 ± 0.008 [exp] ± 0.093 [th] • Vcd=0.225 ± 0.004 [exp] ± 0.022 [th] • Relies on correct shape and normalization of the form factors Marina Artuso WG1 CKM 2006

  17. CLEO-c untagged form factor analysis Combine measured |Vcx|f+ (0) with FNAL-MILC-HPQCD value for f+(0)PRL 94, 011601 (2005) Marina Artuso WG1 CKM 2006

  18. A check on the theory CLEO-c results based on 281 pb-1 (tagged) BR(D mn)=(4.40.70.1)10-4 BR(D  en) <2.410-5 BR(D  tn) <3.110-3 (more details on Stone’s talk) 50 signal candidates, 2.8 bgd Ratio D+→m+n does not depend upon Vcd Missing mass2 = (Ebeam-Emu)2-(pD-pm)2 (GeV)2 Marina Artuso WG1 CKM 2006

  19. . Comparison with FNAL-MILC-HPQCD predictions Data and theory are consistent within error Marina Artuso WG1 CKM 2006

  20. W branching ratios and Vcs • LEP-2 performed measurements sensitive to |Vcs| from on-shell W± decays: • Using: |Vud|2+|Vus|2+|Vub|2+|Vcd|2+ |Vcb|2=1.0476 ±0.0074 |Vcs| =0.976 ±0.014 • Error includes contributions from uncertainties on as and other CKM parameters, but is dominated by ±0.013 from the measurements of the W branching fractions • DELPHI tagged W+ cs analysis |Vcs| =0.94 ±0.014 +0.32-0.26 Marina Artuso WG1 CKM 2006

  21. Neutrino/anti-neutrino interactions and Vcd • Method: n+dc+m  |Vcd|2Bm [average semileptonic branching ratio of charm] <|Vcd|2Bm>=(0.4630.034)x10-2 [pdg 2006] n - Bm= 0.0873 0.0052 |Vcd|2 c d |Vcd|=0.230  0.011 (5% accuracy) Marina Artuso WG1 CKM 2006

  22. Summary • Best Vcs direct determination, using Gexp(Ken) and lattice form factors: • Best Vcd direct determination from n,n interactions • With these inputs and |Vcb|=(41.60.6)x10-3 [pdg 2006] unitarity constraint on the 2nd row gives: Tagged fit Untagged fit Error dominated by theoretical uncertainty in |Vcs| Marina Artuso WG1 CKM 2006

  23. Future prospects • CLEO-c expects to accumulate 750 pb-1 at the y(3770)increased statistics will allow to pin down shape of form factors and constrain theoretical calculations • Further refinements of lattice calculations (now dominating errors) are under way • Goal to determine |Vcs| and |Vcd| down to a few % accuracy Marina Artuso WG1 CKM 2006

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