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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 Reconstruction techniques Results: branching fractions, form factors, V cs and V cd Projections 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 • Reconstruction techniques • Results: branching fractions, form factors, Vcs and Vcd • Projections • Summary Bo Xin Purdue University CLEO collaboration Lake Louise Winter Institute, Feb 18 - 23, 2008 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 (281/pb) 30X MARK III 15X BES II SVX CLEO has world’s largest data set at 3.770 GeV • Advantages at (3770) • Pure , no additional particles • Low multiplicity • High tagging efficiency Bo Xin

  4. Analysis Technique • 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: • Define • The absolute branching fraction is Tagging creates a single D beam of known 4-momentum Bo Xin

  5. D tagging at CLEO-c (281/pb of Data) World’s largest data set at 3.770 GeV Pure DD, zero additional particles, ~5-6 charged particles per event ~3.1x 105 D0 and ~1.6 x 105 D+ tags Reconstructed from ~1.8 x 106 DD events We tag ~25% of the events, compared to ~0.1% of B’s at the Y(4S) Bo Xin

  6. Reconstruction of Semileptonic Decays S/N ~ 40/1, Compared to Belle 282/fb – 1000xCLEO-c ~220 signal events, S/N ~ 4/1 S/N ~ 300/1, Compared to Belle 282/fb – 1000xCLEO-c ~2700 signal events, S/N ~ 20/1 69928 679684 • Extract yields from U distributions and measure branching fractions with multiple tag modes separately and combined • Study form factors and CKM matrix elements using efficiency-corrected decay rate distributions 29520 291055 PRELIMINARY Bo Xin

  7. Neutrino Reconstruction (Untagged) • Hermeticity and excellent resolution of the CLEO-c detector • Simultaneously fit Mbc distributions of the 4 signal modes in 5 q2 bins to extract d(BF)/dq2 and integrate to get branching fractions. Larger signal yields, also larger backgrounds Bo Xin

  8. DK/πe+ Branching fractions CLEO-c Tagged/untagged consistent, 40% overlap, DO NOT AVERAGE Isospin Invariance: (From Tagged analysis) CLEO-c most precise! Theoretical precision lags experiment Bo Xin

  9. q2 resolutions and Raw q2 distributions q2 resolution Raw q2 distribution CLEOIII(Y(4S)): q2 ~ 0.4 GeV2 CLEO-c((3770)): q2 ~ 0.012GeV2 q2 ~ 0.012GeV2 D0→K-e+ν D0→K-e+ν ~7000 events S/B > 300/1 background in blue • Excellent q2 resolution and S/B ratio • To find the absolute decay rate, need to subtract background and apply efficiency corrections. q2 ~ 0.011GeV2 D0→π-e+ν D0→π-e+ν ~700 events S/B ~40/1 background in blue PRELIMINARY Bo Xin

  10. Fit to the Absolute Decay rates Fit to Simple Pole Model Shown PRELIMINARY Simple Pole Model Modified Pole (BK) Model Hill Series parameterization Bo Xin

  11. FNAL-MILC-HPQCD (Curve courtesy Andreas Kronfeld) Assuming Vcs = 0.97450.0008 (CKM unitarity) Form factors as a stringent test of LQCD Removing the kinematic terms reveals the form factor Modified Pole (BK) Model shown Bo Xin

  12. Simple Pole Model D → K e+ ν My average CLEO-c has 1st measurements of Mpole for D+ Important consistency check! Bo Xin

  13. Modified Pole (BK) Model D → π e+ ν BK parameterization α~1.75 CLEO-c values > 10σ away Compatible Physical basis of BK model not supported 0.32(5) My average Consistent LQCD precision(10%) lags experiments (4%) 0.634(18)(9)(8) For D → K e+ν, CLEO-c αvalues > 27σ away from BK physical value, LQCD precision (10%) lags experiments (2%) ! Bo Xin

  14. Becher-Hill series parameterization Dashed lines show 1σ region • Both Linear “series(2)” and quadratic “series(3)” parameterization describes data well • Quadratic “series(3)” a2 not well-determined with current statistics • As data does not support physical basis for the pole & modified pole models, the model independent Becher-Hill series parameterization is used for |Vcx|. Bo Xin

  15. Vcs and Vcd Results Expt. uncertainties Vcs <2% Vcd~4% Theory 10% Combine measured |Vcx|f+(0) values using Becher-Hill parameterization with (FNAL_MILC-HPQCD) forf+(0) Tagged/ untagged consistent, 40% overlap DO NOT AVERAGE CLEO-c: Best determination of Vcs, and Vcd in good agreement with PDG Bo Xin

  16. Projections with 818/pb data • Statistical uncertainties will be reduced by a factor of • Most systematic uncertainties are being reevaluated. some are expected to be reduced. 281/pb 818/pb 281/pb 818/pb NOT CLEO-c official I. Shipsey Aspen 2008 Winter Conference Bo Xin

  17. Summary What we have achieved (281/pb) • Most precise B(D  K e+) and B(D   e+). • Most precise measurements of f+(0) and shape for D   e+ . • Best direct measurement of |Vcs|. • Most precise determination of |Vcd| from semileptonic decays. • More stringent tests of theory for D  K/ e+f+(0) and shape. • Reduced uncertainties on |Vcs| and |Vcd|. What we are going to achieve (818/pb) We are eagerly awaiting more precise LQCD calculations of semileptonic form factors. Bo Xin

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