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Study of DK/ π e +  and measurement of |V cs | and |V cd | at CLEO-c

. K -. K +.  -. e +. Study of DK/ π e +  and measurement of |V cs | and |V cd | at CLEO-c. Introduction Analysis technique Results: (CLEO-c final tagged) branching fractions, form factors, | V cs | and |V cd | Summary. Bo Xin Purdue University CLEO collaboration.

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Study of DK/ π e +  and measurement of |V cs | and |V cd | at CLEO-c

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  1. K- K+  - e+ Study of DK/πe+ and measurement of |Vcs| and |Vcd| at CLEO-c • Introduction • Analysis technique • Results: (CLEO-c final tagged) branching fractions, form factors, |Vcs| and |Vcd| • Summary Bo Xin Purdue University CLEO collaboration APS April Meeting, May 2 - 5, 2009 Bo Xin

  2. * * • Gold-plated modes are P  P semileptonic transitions as they are the simplest modes for both theory and experiment: • Cabibbo favored : • Cabibbo suppressed : Introduction • Semileptonic decays are an excellent laboratory to study Weak Physics QCD Physics • Assuming theoretical calculations of form factors, we can extract |Vcs| and |Vcd| • Since |Vcs| and |Vcd| are tightly constrained by unitarity, we can check theoretical calculations of the form factors • Tested theory can then be applied to B semileptonic decays to extract |Vub|. Bo Xin

  3. p/p = 0.6% at 800 MeV/c E/E = 2% at 1 GeV, 5% at 100 MeV 93% coverage (charged and neutral) Excellent electron and particle ID CLEO-c The CLEO-c detector and data sample CLEO III Today’s results (818/pb) 86X MARK III 25X BES II SVX CLEO has world’s largest data set at (3770) • Advantages at (3770) • Pure , no additional particles • Large branching fractions to low multiplicity modes → High tagging efficiency Bo Xin

  4. e+e-y(3770)DD Analysis Technique (tagged) • Candidate events are selected by reconstructing a D, called a tag, in several hadronic modes • Then we reconstruct the semileptonic decay in the system recoiling from the tag. • Two key variables in the reconstruction of a tag: • For semileptonic D : • The partial decay rates are: from fits to U from fits to Mbc efficiency matrix inversed Tagging creates a single D beam of known 4-momentum An absolute measurement Bo Xin

  5. D tagging at CLEO-c 818 pb-1 @3770 World’s largest data set at 3.770 GeV Pure DD, zero additional particles, ~5-6 charged particles per event ~6.6x 105 D0 and ~4.8 x 105 D+ tags reconstructed from ~5.4 x 106 DD events We tag ~20% of the events, compared to ~0.1% of B’s at the Y(4S) Bo Xin

  6. Fits to the U Distributions for DK-e (818/pb) Yield (all tags/q2 ): 14121±121 4 of 27 U fits • We perform binned likelihood fits to U distributions in each q2 bin and tag mode • Signal shapes are taken from signal MC, smeared with double Gaussians • background shapes are taken from MC with all DD and non-DD decays Belle luminosity = 282/fb = 350xCLEO-c Phys.Rev.Lett.97:061804(2006) Bo Xin

  7. Fits to the U Distributions for Dπ-/π0 /K0 e (818/pb) Belle luminosity = 282/fb = 350xCLEO-c 4 of 21 U fits Phys.Rev.Lett.97:061804(2006) Measurements for D+ modes have not been made at B factories! 4 of 42 U fits 4 of 54 U fits Bo Xin

  8. DK/πe+ : Fits to the dΓ/dq2 Distributions Fit to Becher-Hill Series 2 par (a0 a1) Other form factor parameterizations exist, but are only used as functional forms as their physical pictures are not supported by the data 3 par (a0 a1 a2) Simultaneous fits to isospin conjugate modes are also performed Bo Xin

  9. DK/πe+ Branching fractions The branching fractions are extracted from the form factor fits NEW NEW Precision measurements from BABAR/Belle/CLEO-c. CLEO-c most precise. Theoretical precision lags experiment. Bo Xin

  10. D  K e+ Form Factor: Test of LQCD Form factor measures probability hadron will be formed 1 σ bands (stat and syst) by FNAL-MILC-HPQCD NEW Assuming |Vcs |= 0.973340.00023 (CKM unitarity) Modified pole model used to compare with LQCD α : CLEO-c prefers smaller value for shape parameter than others f+ (0): experiments (1.2%) consistent with LQCD (10%). CLEO-c is most precise. Theoretical precision lags. NEW Bo Xin

  11. Dπe+ Form Factor: Test of LQCD Form factor measures probability hadron will be formed NEW 1 σ bands (stat and syst) by FNAL-MILC-HPQCD Assuming |Vcd |= 0.22560.0010 (CKM unitarity) Modified pole model used to compare with LQCD α : CLEO-c measurements are compatible with LQCD f+ (0): experiments (2.9%) consistent with LQCD (10%). CLEO-c is most precise. Theoretical precision lags. NEW Bo Xin

  12. |Vcs | and |Vcd | Results The data determine |Vcs(d)|f+(0). To extract |Vcs(d)|, we combine the measured |Vcs(d)|f+(0)values using Becher-Hill parameterization with (FNAL-MILC-HPQCD) forf+(0) * CLEO-c: the most precise direct determination of |Vcs | NEW * PDG2002 CLEO-c: νN remains most precise determination NEW Bo Xin

  13. Summary • Most precise B(D  K e+) and B(D   e+). • Most precise measurements of f+(0) and shape for D  K/ e+ . • Very stringent tests of unquenched LQCD. • Best direct measurement of |Vcs|. • Most precise determination of |Vcd| from semileptonic decays. • The work uses the entire CLEO-c sample at Ψ(3770). • The results are about to be submitted to Phys. Rev. D. • These will remain the best results before BESIII do the same measurements. • We are eagerly awaiting more precise LQCD calculations of semileptonic form factors. Bo Xin

  14. Vub b Backup slides (summer 2008) 11- 17% e.g. HPQCD &FNAL Expt. 5% q2>16 GeV Bo Xin

  15. l l B n n p p(K) Backup slides Theory + Experiment = Precision Flavor Physics Now The discovery potential of B physics is limited by systematic errors from QCD: (ρ, η) Δmd,s ~|Vub| One of the most important goals of B physics Suffer from large theory uncertainty Measured experimentally HQS Tightly constrained by CKM unitarity D Bo Xin

  16. Form Factor: D→ P e , which parameterization to choose? PRELIMINARY When the shape parameters are not fixed, each parameterization is able to describe the data with a comparable χ2 probability. As data do not support physical basis for the pole & modified pole models, the model independent Becher-Hill series parameterization is used for |Vcx|. Bo Xin

  17. The Global Branching Fractions • The tag yield can be expressed as • The yield of tags with a semileptonic decay can be expressed as • The branching fraction of the semileptonic decay • The branching fraction determined by tagging is an absolute measurement, independent of the integrated luminosity and number of D mesons in the data sample. from fits to U from fits to Mbc Bo Xin

  18. Fits to the Partial Rates • Define q2 (the invariant mass of the e+νe pair): • The method described above can also be used to obtain partial branching fractions, or equivalently, partial rates in q2 bins. • The theoretically predicted partial rates • Use the least squares method to fit to the partial rates from fits to U from fits to Mbc efficiency matrix inversed Bo Xin

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