1.  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 cut on and fit to  For semileptonic D U peaks at zero for real semileptonic decays Tagging creates a single D beam of known 4-momentum 818 pb -1 @3770 Pure DD, zero additional particles, ~5-6 charged particles per event ~4.8 x 10 5 D + tags reconstructed from ~2.4 x 10 6 D + D - events Introduction CLEO’s measurements most precise for ALL modes; 4 modes observed for the first time Normalized to PDG Precision Measurements: The Global Global Branching Fractions D Tagging at 3770 MeV Summary Measurement of the D  ηe Form factor Study of dΓ/dq 2 in D→ηeν Bo Xin, Ian Shipsey, Purdue University, CLEO Collaboration Observation of D +  ’ e and study of D +  e Upper limit for D  e  D→K/π eν are the gold-plated modes to measure |V cs | and |V cd | and to test LQCD  Observations and form factor studies of new modes are desired to gain a complete picture of charm semileptonic decays  Nine exclusive D semileptonic BF’s (56pb -1 ) + D  K/π e (281pb -1 )  Inclusive semileptonic branching fractions (281/pb):  There is room left for new semileptonic modes with small branching fractions. Two of these modes have been found using 281 pb-1 of data  Study of D→η/η’ eν may shed light on the contents of the η/η’ mesons. First observation of D→ηeν PRL.102: 081801(2009) PRL.99: 191801(2007)  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 M bc In this analysis, using this global method, we will present  Improved branching fraction measurement for D→ηeν  Observation of D→η’eν and measurement of its branching fraction  Improved upper limit for D→Φeν D +  e branching fraction Observation of D +  ’ e Without applying MC/data correction factors and systematic uncertainties Consistent  Signal (2-tail CB) and background shapes (2 nd order polynomial) are taken from signal MC and generic MC.  Each fit has two floating parameters: signal yield and background yield. One event observed in the signal region (-60, 60) MeV. And one in the background region. 90% C.L. interval: (0.00,3.58), corresponds to a 90% C.L. upper limit of 0.8x10 -4 (without MC/data corrections) First Form Factor Measurement for D→ηeν  The total estimated number of background events for two η decay modes, with statistical uncertainties only, is 0.0425±0.0257  After including the systematic uncertainties, the total number of background events is 0.0425±0.0284  According to Poisson statistics, with the uncertainty on the background accounted for with a toy MC experiment, the probability for this background to fluctuate into 5 events is 9.7 x 10 -9, which corresponds to 5.6 standard deviations.  The branching fractions, with asymmetric Poisson errors First observation of D  ’e Without applying MC/data correction factors and systematic uncertainties  Background level is high  Main background: D + →  e +FSR or unassociated noise photons  B(D→η’eν)<3.9x10 -4 When statistics allow ( D→ηeν in our case), The method described above can also be used to obtain partial branching fractions, or equivalently, partial rates in q 2 bins. The theoretically predicted partial rates (P→P transition) from fits to U from fits to M bc Inverse of the efficiency matrix Use the least squares method to fit to the partial rates Make fits to the partial rates using several form factor parameterizations to extract form factor parameters and branching fraction ( First form factor study for D→ηeν) B( D→ηeν) using this derived method supersedes the global B(D→ηeν), which serves as a cross-check.  Each η decay mode is divided into 3 q 2 bins; each plot is for all tag modes combined, due to limited statistics.  Signal (2-tail CB) and background shapes (2 nd order polynomial) are taken from signal MC and generic MC.  Each fit has two floating parameters: signal yield and background yield.  Total yield: 110.2±12.7 (All tag modes/q2 combined fit: 113.0±12.8) Distributions of kinematic variables in D +  e  Br(D  e ): consistent with but more precise than our previous result  First observation of D  ’e. 5 events consistent with signal, significance: 5.6 sigma  Improved upper limit for D  e  First form factor measurement of D +  e MC/data correction factors applied