Studies of the decays D0→KS0K−π+ and D0→KS0K+π−

The first measurements of the coherence factor RK⁰SKπ and the average strong–phase difference δK⁰SKπD in D⁰ → K⁰S K∓π± decays are reported. These parameters can be used to improve the determination of the unitary triangle angle in B⁻ → D¯K⁻ decays, where D¯ is either a D⁰ or a D¯⁰ meson decaying to the same final state, and also in studies of charm mixing. The measurements of the coherence factor and strong-phase difference are made using quantum-correlated, fully reconstructed D⁰D¯⁰ pairs produced in e⁺e⁻ collisions at the ψ(3770) resonance. The measured values are RK⁰SKπ = 0.73 ± 0.08 and δK⁰SKπD = (8.3 ± 15.2)° for an unrestricted kinematic region and RK*K = 1.00 ± 0.16 and δK*KD = (26.5 ± 15.8)° for a region where the combined K⁰Sπ± invariant mass is within 100 MeV/c² of the K*(892)± mass. These results indicate a significant level of coherence in the decay. In addition, isobar models are presented for the two decays, which show the dominance of the K*(892)± resonance. The branching ratio B(D⁰ → K⁰S K⁺π⁻)/B(D⁰ → K⁰S K⁻π⁺) is determined to be 0.592 ± 0.044(stat.) ± 0.018(syst.), which is more precise than previous measurements.