Study of decay dynamics and $CP$ asymmetry in $D^+ \to K^0_L e^+ \nu_e$ decay

摘要: Using 2.92~fb−1 of electron-positron annihilation data collected at s√=3.773~GeV with the BESIII detector, we obtain the first measurements of the absolute branching fraction B(D+→K0Le+νe)=(4.481±0.027(stat.)±0.103(sys.))% and the CP asymmetry AD+→K0Le+νeCP=(−0.59±0.60(stat.)±1.48(sys.))%. From the D+→K0Le+νe differential decay rate distribution, the product of the hadronic form factor and the magnitude of the CKM matrix element, fK+(0)|Vcs|, is determined to be 0.728±0.006(stat.)±0.011(sys.). Using |Vcs| from the SM constrained fit with the measured fK+(0)|Vcs|, fK+(0)=0.748±0.007(stat.)±0.012(sys.) is obtained, and utilizing the unquenched LQCD calculation for fK+(0), |Vcs|=0.975±0.008(stat.)±0.015(sys.)±0.025(LQCD).