Experimental Study Of D⁺?K_S,L⁰K⁺??⁰? At BES?

Using 2.93 fb^-1 of electron-positron annihilation data collected at the ??3770?resonance with the BESIII detector on the BEPCII electron-positron storage,we mea-sure the branching fractions and related CP violation in D⁺ ? K_S⁰K⁺,D⁺ ?K_S⁰K⁺?⁰,D⁺ ? K_L⁰K⁺ and D⁺ ? K_L⁰K⁺?⁰.The results are:B?D⁺ ? K_S⁰K⁺?=?3.06 ± 0.09 ± 0.08?× 10-3,B?D⁺ ? K_L⁰K⁺?=?3.23 ± 0.11 ± 0.11?× 10-3,B?D⁺ ? K_S⁰K⁺?⁰?=?5.16 ± 0.21 ± 0.23?× 10-3,B?D⁺ ? K_L⁰K⁺?⁰?=?5.22 ± 0.22 ± 0.21?× 10-3.and A_CP^D?K_S⁰K=(^-1.5 ± 2.8 ± 1.6)%,A_CP^D?K_L⁰K=?-3.0 ± 3.2 ± 1.2?%,A_CP^D?K_S⁰K?⁰=?1.4 ± 4.0 ± 2.4?%,A_CP^D?K_L⁰K?⁰=?-0.9 ± 4.1 ± 1.6?%.The branching fraction for D⁺ ? K_S⁰K⁺ is consistent with the PDG value,and the branching fractions for D⁺ ? K_S⁰K⁺?⁰,D⁺ ? K_L⁰K⁺ and D⁺ ? K_L⁰K⁺?⁰ are measured for the first time.Beside of using branching fraction measurement,we al-so measure CP asymmetry by dividing region on Dalitz Plot for three^-body decays D⁺ ? K_S,L⁰K⁺?⁰ and do not find evidence for CP violation.We perform an analysis of the D⁺ ? K_S⁰K⁺?⁰ Dalitz plot using the same data sample.We test several sets with different contributing intermediate resonances,and find the Dalitz Plot is mainly represented by a combination of seven quasi-two-body decay channels?K*?892?⁺K_S⁰ K*?892?0K⁺,K*?1410?⁺K_S⁰ K*?1410?0K⁺,K₀^*?1430?⁺K_S⁰,K2*?1430?⁺K_S⁰,???2*?1430?0K⁺?plus a non-resonant component.Using the fit frac-tions from this analysis,relative branching ratios of each intermediate resonances are measured.Using double^-tag technique,we study ?E systematic uncertainty of six charged and three neutral D meson decay modes,which value is about 0.1%level?...