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. K -. K +. -. e +. Absolute Branching Fractions and Form Factor Measurements in DK/ π e + . Introduction Branching Fractions Form Factors Summary. Bo Xin Purdue University CLEO collaboration. APS April Meeting, Apr 14-Apr 17, 2007. *. *. Introduction.

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## Absolute Branching Fractions and Form Factor Measurements in DK/ π e +

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****K- K+ - e+ Absolute Branching Fractions and Form Factor Measurements in DK/πe+ • Introduction • Branching Fractions • Form Factors • Summary Bo Xin Purdue University CLEO collaboration APS April Meeting, Apr 14-Apr 17, 2007 Bo Xin****** Introduction • Semileptonic decays are an excellent laboratory to study • Gold-plated modes are P P semileptonic transitions as they are the simplest modes for both theory and experiment: • Cabibbo favored : • Cabibbo suppressed : • Main goals of the analyses: • Measure efficiency-corrected absolutely-normalized decay rate distributions and form factors • Measure form factor parameters to test LQCD and model predictions • We analyze both D0 and D+ decays. By isospin invariance • . • . This is a nice cross check and adds statistics to improve statistical precision. Weak Physics QCD Physics Bo Xin**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 analyses (281/pb) 30X MARK III 15X BES II SVX • Advantages at (3770) • Pure , no additional particles • Low multiplicity • High tagging efficiency • The generic MC sample (40X luminosity of the data). Bo Xin**Tagged Reconstruction of Semileptonic Decays**• 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**D0 and D+ tag yields in 281/pb of Data**Examples of Mbc for tag modes in the data ~30% event tagging efficiency ~20% event tagging efficiency One D tag candidate per D tag flavor per mode is chosen. Bo Xin**69928**679684 29520 291055 Fit to U distributions U = Emiss– |Pmiss| (GeV) Bo Xin**Neutrino Reconstruction (Untagged)**The Reconstruction Algorithm: • Find an event with a signal electron and a signal K or π • Reconstruct the event missing (neutrino) 4-momentum • Calculate ΔE and scaled Mbc • is the scale factor for Pmiss that sets Δ E to zero. 134749 14397132 45029 584688 Bo Xin**DK/πe+ Branching fractions**Tagged/untagged consistent, 40% overlap DO NOT AVERAGE Isospin Invariance: (From Tagged analysis) Bo Xin**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 Note the background in blue 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 Bo Xin**Fit to the Absolute Decay rates**D0→K-e+ν D+→Kse+ν Tagged Modified Pole Model Shown D0→π-e+ν D+→π0e+ν Simple Pole Model Modified Pole (BK) Model Hill Series parameterization Bo Xin**Form factors as a stringent test of LQCD**LQCD: C. Aubin et al., PRL 94 011601 (2005). LQCD DATA FIT CLEO preliminary LQCD DATA FIT Vcd = 0.22380.0029 Vcs = 0.97450.0008(CKM unitarity) LQCD precision lags experiment. Bo Xin**Vcs and Vcd Results (CLEO preliminary)**Combine measured |Vcx|f+(0) values using Becher-Hill parameterization with (FNAL_MILC-HPQCD) forf+(0) Tagged/ untagged consistent, 40% overlap DO NOT AVERAGE Expt. uncertainties Vcs <2% Vcd~4% Theory 10% CLEO-c: Best determination of Vcs / Vcd in good agreement with PDG Bo Xin**Summary**• We have presented preliminary results for D K/ e+ branching fractions and form factors using the CLEO-c 281/pb data sample collected at the (3770). • These results obtained from the tagged and untagged analyses are consistent and are being combined (will be available soon). • Together, they represent the most precise charm semileptonic branching fraction measurements and form factors to date. • Using the unitarity of the CKM matrix we obtain the most precise values of f+(0) for D K/ e+ . • Using three flavor unquenched LQCD we have made the most precise determination of |Vcs| and |Vcd| is in good agreement with PDG. Bo Xin

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