Measurements Of Branching Fractions For D~+→(?)~0e~+v_e, D~+→K_S~0K_S~0K~+(π~+),D~0→K_S~0K_S~0 And D~0→K_S~0K_S~0K_S~0

By analyzing 2.93 fb-1 of data taken at 3.773 GeV with the BES-Ⅲ detector operated at the BEPC-Ⅱ collider,we measure the absolute branching fraction of the semileptonic decay D+→(?)0e+ve to be B(D+→(?)0e+ve)=(8.59±0.14± 0.21)% using K0→π0π0 for the first time.Utilizing the measured value of B(D0→ K-e+ve),the isospin symmetry parameter of D meson decay is determined to be:R= (BD0→κ-e+ve/BD+→κ0e+ve)×(τD+/τD0)=0.969±0.025.This measurement can shed light on the study of strong and weak effects in charmed meson decays and could be used to extract the form factor of hadronic weak current f+k(0)or the quark mixing matrix element |Vcs|,which are important to calibrate the lattice quantum chromody-namics and test the unitarity of the quark mixing matrix.By analyzing the same data sample,we study some hadronic decays containing two KS0 mesons.We measure the branching fractions for D+→KS0KS0K+,D+→ KS0KS0π,D0→KS0KS0 and D0→KS0KS0KS0 to be B(D+→KS0KS0K+)=(2.53± 0.05±0.12)×10-3,B(D+→KS0KS0π+)=(2.68±0.06±0.12)×10-3,B(Do→ KS0KS0)=(1.67±0.13±0.12)×10-4 and B(D0→KS0KS0KS0)=(7.32±0.35± 0.45)×10-4.The branching fraction for D+→KS0KS0π+ is measured for the first time,and the branching fractions for D+→KS0KS0K+,D0→KS0KS0 and D0→ KS0KS0KS0 are consistent with the PDG averaged branching fractions within errors,but with significant better precisions.