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 0 0 0 0 (3770) , D D D D K e K | | miss miss P E U 2 2 4 2 D beam bc beam D E E E M E /c p /c 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 Normalized to PDG * 0 0 branching fractionsare for56/pb / / / branching fractionsare for818/pb D Ke D K Ke Precision Measurements: The Global Global Branching Fractions D Tagging at 3770 MeV Summary Measurement of the Dηe 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 ) + DK/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. 0 ( ) (6.2 0.2 0.2)% ( ) (15.0 0.5 0.5)% excl semil excl semil BD BD 0 ( ) (6.46 0.17 0.13)% ( ) (16.13 0.20 0.33)% incl semil incl semil BD BD 0 1.3 4 1 1 1.0 4 4 1 1 46 events (281 pb ),fo ( (1270) ) ( (1270) ) (2.5 0.2) 10 ( ) (13.3 2.0 0.6) 10 ( ' ) 3.5 10 rm factorstudy doablew ith 8 c 18pb BD K e BK K BD e BD e 1 4 ( ) 1.6 10 lose to theoretical pre diction,possible observation w ith 818pb isnotexpected in the absence ofm ixing betwee n the and BD e First observation of D→ηeν PRL.102: 081801(2009 ) PRL.99: 191801(200 7) The branching fraction of the semileptonic decay The branching fraction determined by tagging is an absolute measurement, independent of the integrated luminosity and , , , , / , w here / tag SL tag tag SL SL tag SL tag tag tag SL tag N N B N N 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 :84.9 11.6 Yield events events Yield 3 . 5 1 . 28 : Without applying MC/data correction factors and systematic uncertainties Consiste nt 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) 2 2 ' 2 2 3 2 ' 3 | | | ( )| 24 F Qq predicted i P i i G V d f q p dq 1 , 1 j ij tag SL j measured i i D D tag N B N from fits to U from fits to M bc Inverse of the efficiency matrix 2 1 , ( )[cov( , )]( ) measured predicted measured predicted i i i j j j ij • 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(De): 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
