Measurement of the D0→ K- Pi+ strong phase difference at BESIII.
ABSTRACT :
Quantum correlated D0 and D0bar meson pairs are produced at electron-positron collider at a Centre of Mass energy of 3.773 GeV and a data sample of 2.92 fb-1 is collected by the BESIII detector in China. The asymmetry (A_CP) of the branching fraction (B) of D0→ K-Pi+ in CP-odd and CP-even eigenstates is found to be (12.7±1.3 (stat)±0.7(syst))×10^-2. The A_CP is then used to extract the strong phase difference (delta KPi) between the doubly Cabibbo-suppressed process D0 → K-Pi+ and the Cabibbo-favoured process D0 → K-Pi+. The cosine of the strong phase difference, using world-average values of external parameters, is 1.02±0.11±0.06±0.01, where the uncertainties are statistical, systematic and the uncertainties arise due to the usage of external inputs. This is the most precise measurement of delta KPi to date.