Study Of D~0-(?)~0 Mixing And CP Violation In D~0?K~+?~-?~0

The D⁰-???⁰ mixing and CP violation in charm sector are predicted to be very small by Standard Model?SM?.Hence they are sensitive to new physics beyond SM,and useful to the precise test of SM,although,D⁰-???⁰ mixing is difficult to quantify in SM.There are observations of mixing in two mode of K? or K??? wrong-sign decays,but CP violation is not yet observed.It is important to study D⁰-???⁰ mixing in D⁰ three-body decays because of the different sensitivity dependence on decay mode.This thesis is based on a total integrated luminosity of 921 fb-1 collected on or near??4S?and on T?5S?by Belle experiment at the KEKB electron-positron asymmetric-energy collider.The D⁰ candidates are reconstructed with chain D*?D⁰?s,D⁰?K????????0 and conjugated decays,here ?s denotes low momentum pion and its charge tags the flavor of neutral D meson at production.The D⁰ decay vertex and produc-tion vertex are obtained from 3-dimensional vertex fit to obtain D⁰ proper lifetime and its error.The wrong-sign?WS?events D⁰? K+?-?0 and the right-sign?RS?events D⁰?K-?+?0 are both reconstructed for further analysis.Through invari-ant masses M-Q 2-dimensional fit,1142232±3077 RS signals and 2653±100WS sig-nals are obtained,respectively.Then WS-to-RS ratio Rws is?0.2322 ±0.0069?%,which is improved by an order of magnitude to current result,and CP asymmetry ACP=(RXSD⁰-R_WS^D0)/(R_WS^D0+R_WS^D0)= 0.002±0.029 is improved twice comparing to current result.A Dalitz analysis is performed for RS events,and the intermediate resonances are studied.The fit fractions of each component are also calculated.This results are used to describe the Cabibbo-Favored process amplitude for time-dependent Dalitz analysis of WS events.The Dalitz analyses for D⁰ sample and D⁰ sample are used to measure CP violation.No significant sign of CP violation is observed.A time-dependent Dalitz analysis is performed for WS events.Seven resonances are chosen to described the doubly Cabibbo-Suppressed process.The mixing parame-ters are fitted as x"/r0=0.325±0.071,and y"/r0 =-0.092±0.084,and with smaller uncertainty than current measurement.The hypothesis of no D⁰-???⁰ mixing is excluded with 3.4? confidence level.The Belle ? plans to collect 50 ab-1 data and has better time resolution ?=140 fs which is improved twice than that of BaBar and Belle,the sensitivity of D⁰-???⁰ mixing parameters will have about one magnitude improvement to current experimental results,without considering background effects in Monte Carlo study.