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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 | 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| • Summary Bo Xin Purdue University CLEO collaboration APS April Meeting, Apr 12 - 15, 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. from fits to U from fits to Mbc 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 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 (tagged) Belle luminosity = 282/fb = 1000xCLEO-c 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, hence excellent understanding of the background • 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 Precision measurements from BABAR/Belle/CLEO-c. CLEO-c most precise. Theoretical precision lags experiment. Bo Xin

  9. Absolute dΓ/dq2 Distributions Fit to Simple Pole Model Shown PRELIMINARY Simple Pole Model Modified Pole (BK) Model Hill Series parameterization Bo Xin

  10. D0 K -e+ Form factors: test of LQCD FNAL-MILC-HPQCD (Curve courtesy Andreas Kronfeld) Assuming Vcs=0.9745 CKM Unitarity Modified pole model used as example Shape: CLEO-c prefers smaller value for α Normalization: experiments (2%) consistent with LQCD (10%). Theoretical precision lags. Bo Xin

  11. D0  -e+ Form factors: test of LQCD FNAL-MILC-HPQCD Assuming Vcd = 0.22380.0029 (CKM Unitarity) Modified pole model used as example Shape: experiments compatible with LQCD Normalization: experiments (4%) consistent with LQCD (10%). CLEO-c is most precise. Theoretical precision lags. Bo Xin

  12. | | 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) PRELIMINARY PRELIMINARY Tagged/ untagged consistent, 40% overlap DO NOT AVERAGE CLEO-c: Best determination of |Vcs|, and |Vcd| in good agreement with PDG Bo Xin

  13. 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. • Statistical uncertainties will be reduced by a factor of • Most systematic uncertainties are being reevaluated. Some are expected to be reduced. • More stringent tests of theory -- f+(0) and shape for D  K/ e+ . • 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

  14. Backup slides Isospin Invariance: (from tagged analysis) Systematics missing…. Bo Xin

  15. Reconstruction of Semileptonic Decays (tagged) 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 • A Belle plot here? for comparision 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

  16. 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

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

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

  19. 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

  20. Becher-Hill series parameterization Dashed lines show 1σ region • Both linear “series(2)” and quadratic “series(3)” parameterization describes data well • Quadratic term 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

  21. 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

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