With t-channel ρ, f 2 (1270) exchange and the ππ → ρρ → ππ box diagram contribution, we reproduce the ππ isotensor S-wave and Dwave scattering phase shifts and inelasticities up to 2.2 GeV quite well in a K-matrix formalism. The t-channel ρ exchange provides repulsive negative phase shifts while the t-channel f 2 (1270) gives an attractive force to increase the phase shifts for ππ scattering above 1 GeV, and the coupled-channel box diagram causes the inelasticities. The implication to the isoscalar ππ S-wave interaction is discussed.
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.
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