Amplitude analysis of the decays D0 → π+π−π+π− and D0 → π+π−π0π0*

Using e+e− annihilation data corresponding to an integrated luminosity of 2.93 fb−1 taken at the center-of-mass energy √s = 3.773 GeV with the BESIII detector, a joint amplitude analysis is performed on the decays D0 → π+π−π+π− and D0 → π+π−π0π0 (non-η). The fit fractions of individual components are obtained, and large interferences among the dominant components of the decays D0 → a1(1260)π, D0 → π(1300)π, D0 → ρ(770)ρ(770), and D0 → 2(ππ)S are observed in both channels. With the obtained amplitude model, the CP-even fractions of D0 → π+π−π+π− and D0 → π+π−π0π0 (non-η) are determined to be (75.2 ± 1.1stat. ± 1.5syst.) % and (68.9 ± 1.5stat. ± 2.4syst.)%, respectively. The branching fractions of D0 → π+π−π+π− and D0 → π+π−π0π0 (non-η) are measured to be (0.688 ± 0.010stat. ± 0.010syst.)% and (0.951 ± 0.025stat. ± 0.021syst.)%, respectively. The amplitude analysis provides an important model for the binning strategy in measuring the strong phase parameters of D0 → 4π when used to determine the CKM angle γ(φ3) via the B− → DK− decay

Measurement of integrated luminosity of data collected at 3.773 GeV by BESIII from 2021 to 2024

We present a measurement of the integrated luminosity e+e- of collision data collected by the BESIII detector at the BEPCII collider at a center-of-mass energy of Ecm = 3.773 GeV. The integrated luminosities of the datasets taken from December 2021 to June 2022, from November 2022 to June 2023, and from October 2023 to February 2024 were determined to be 4.995±0.019 fb-1, 8.157±0.031 fb-1, and 4.191±0.016 fb-1, respectively, by analyzing large angle Bhabha scattering events. The uncertainties are dominated by systematic effects, and the statistical uncertainties are negligible. Our results provide essential input for future analyses and precision measurements