Measurement of the D → K− π+ π+ π− and D → K− π+ π0 coherence factors and average strong-phase differences in quantum-correlated DD¯ decays

Abstract

The decays D → K−π+π+π− and D → K−π+π0 are studied in a sample of quantum-correlated DD¯ pairs produced through the process e+e− → ψ(3770) → DD¯ , exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fb−1. Here D indicates a quantum superposition of a D0 and a D¯ meson. By reconstructing one neutral charm meson in a signal decay, and the other in the same or a different final state, observables are measured that contain information on the coherence factors and average strong-phase differences of each of the signal modes. These parameters are critical inputs in the measurement of the angle γ of the Unitarity Triangle in B− → DK− decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3π = 0.52−0.10+0.12 and RKππ0 = 0.78 ± 0.04, with values for the average strong-phase differences that are δDK3π=(167−19+31)° and δDKππ0=(196−15+14)°, where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D → K−π+π+π− to yield results that will allow for a more sensitive measurement of γ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6°. [Figure not available: see fulltext.]