Model-independent determination of the relative strong-phase difference between D0 and D¯0→K

Abstract

Crucial inputs for a variety of CP-violation studies can be determined through the analysis of pairs of quantum-entangled neutral D mesons, which are produced in the decay of the ψð3770Þ resonance. The relative strong-phase parameters between D 0 andD 0 in the decays D 0 → K 0 S;L π þ π − are studied using 2.93 fb −1 of e þ e − annihilation data delivered by the BEPCII collider and collected by the BESIII detector at a center-of-mass energy of 3.773 GeV. Results are presented in regions of the phase space of the decay. These are the most precise measurements to date of the strong-phase parameters in D → K 0 S;L π þ π − decays. Using these parameters, the associated uncertainty on the Cabibbo-Kobayashi-Maskawa angle γ=ϕ 3 is expected to be between 0.7°and 1.2°for an analysis using the decay B AE → DK AE , D → K 0 S π þ π − , where D represents a superposition of D 0 andD 0 states. This is a factor of 3 smaller than that achievable with previous measurements. Furthermore, these results provide valuable input for charm-mixing studies, other measurements of CP violation, and the measurement of strong-phase parameters for other D-decay modes.

Determination of Strong-Phase Parameters in D→KS,L0π+π−

“…[12] for the determination of the strong-phase parameters between D 0 andD 0 → K 0 S;L π þ π − . More details are presented in a companion paper [16]. Our data sample was collected from e þ e − annihilations at ffiffi ffi s p ¼ 3.773 GeV, just above the energy threshold for production of DD events.…”

“…DTs are only formed in combinations where there is a maximum of one unreconstructed particle. The selection and yield determination procedures of ST and DT candidates are described in the companion paper [16] and are summarized below. The ST yields, N ST , are listed in the second column of Table I.…”

“…S π þ π − and K 0 L π þ π − signals, respectively. Therefore, in the determination of the DT yields, simulated efficiency matrices are introduced to account for bin migration and reconstruction efficiencies [16]. Studies indicate that neglecting bin migration introduces biases in the determination of c i ðs i Þ that average a factor of 0.7 (0.3) times the statistical uncertainty of this analysis, so it is important to S;L π þ π − vs various tags.…”

“…The values of K i and K 0 i that are used to evaluate N exp i are determined from the flavor-tagged DT yields, where corrections from doubly Cabibbo-suppressed decays, efficiency and migration effects have been applied, which are explained in detail in Ref. [16].…”

“…The details of assigning Δc i (Δs i ) and their uncertainties δΔc i (δΔs i ) are presented in Table VI of Ref. [16]. The measured strong-phase parameters c ð0Þ i and s ð0Þ i are presented in Fig.…”