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By using 6.32 fbβ1 of data collected with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we perform an amplitude analysis of the decay D+s ! K0S +β0 and determine the relative fractions and phase differences of different intermediate processes, which include K0S (770)+, K0S (1450)+, Kβ(892)0β+, Kβ(892)+β0, and Kβ(1410)0β+. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be B(D+s ! K0S +β0) = (5.43 Β± 0.30stat Β± 0.15syst) Γ 10β3.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fbβ1 of e+eβ collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
Using 2.93ββfbβ1 of π+β’πβ collision data taken at a center-of-mass energy of 3.773 GeV by the BESIII detector at the BEPCII, we measure the branching fractions of the singly Cabibbo-suppressed decays π·βπβ’πβ’π to be β¬β‘(π·0βπβ’π+β’πβ)=(1.33Β±0.16Β±0.12)Γ10β3 and β¬β‘(π·+βπβ’π+β’π0)=(3.87Β±0.83Β±0.25)Γ10β3, where the first uncertainties are statistical and the second ones systematic. The statistical significances are 12.9β’π and 7.7β’π, respectively. The precision of β¬β‘(π·0βπβ’π+β’πβ) is improved by a factor of 2.1 over prior measurements, and β¬β‘(π·+βπβ’π+β’π0) is measured for the first time. No significant signal for π·0βπβ’π0β’π0 is observed, and the upper limit on the branching fraction is β¬β‘(π·0βπβ’π0β’π0)<1.10Γ10β3 at the 90% confidence level. The branching fractions of π·βπβ’πβ’π are also measured and consistent with existing results.
Using 2.93ββfbβ1 of π+β’πβ collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the absolute branching fractions of 14 hadronic π·0β’(+) decays to exclusive final states with an π, e.g., π·0βπΎββ’π+β’π, πΎ0πβ’π0β’π, πΎ+β’πΎββ’π, πΎ0πβ’πΎ0πβ’π, πΎββ’π+β’π0β’π, πΎ0πβ’π+β’πββ’π, πΎ0πβ’π0β’π0β’π, and π+β’πββ’π0β’π; π·+βπΎ0πβ’π+β’π, πΎ0πβ’πΎ+β’π, πΎββ’π+β’π+β’π, πΎ0πβ’π+β’π0β’π, π+β’π+β’πββ’π, and π+β’π0β’π0β’π. Among these decays, the π·0βπΎββ’π+β’π and π·+βπΎ0 πβ’π+β’π decays have the largest branching fractions, which are β¬β‘(π·0βπΎββ’π+β’π) = (1.853Β±0.02β’5statΒ±0.03β’1syst)% and β¬β‘(π·+βπΎ0πβ’π+β’π) = (1.309Β±0.03β’7statΒ±0.03β’1syst)%, respectively. The charge-parity asymmetries for the six decays with highest event yields are determined, and no statistically significant charge-parity violation is found.
Relative fractions and phases of the intermediate decays are determined. With the detection efficiency estimated by the results of the amplitude analysis, the branching fraction of DΓΎ s β KβKΓΎΟΓΎΟ0 decay is measured to be Γ°5.42 0.10stat 0.17systΓ%.
Using a data sample of 4.481Γ108ββπβ‘(3686) events collected with the BESIII detector, we report the first observation of the four-lepton-decays π½/πβπ+β’πββ’π+β’πβ and π½/πβπ+β’πββ’π+β’πβ utilizing the process πβ‘(3686)βπ+β’πββ’π½/π. The branching fractions are determined to be [5.48Β±0.31β’(stat)Β±0.45β’(syst)]Γ10β5 and [3.53Β±0.22β’(stat)Β±0.13β’(syst)]Γ10β5, respectively. The results are consistent with theoretical predictions. No significant signal is observed for π½/πβπ+β’πββ’π+β’πβ, and an upper limit on the branching fraction is set at 1.6Γ10β6 at the 90% confidence level. A πΆβ’π asymmetry observable is constructed for the first two channels, which is measured to be (β0.012Β±0.054Β±0.010) and (0.062Β±0.059Β±0.006), respectively. No evidence for πΆβ’π violation is observed in this process.
Using inclusive decays of the J/Ο, a precise determination of the number of J/Ο events collected with the BESIII detector is performed. For the two data sets taken in 2009 and 2012, the numbers of J/Ο events are recalculated to be (224.0Β±1.3)Γ106 and (1088.5Β±4.4)Γ106 respectively, which are in good agreement with the previous measurements. For the J/Ο sample taken in 2017--2019, the number of events is determined to be (8774.0Β±39.4)Γ106. The total number of J/Ο events collected with the BESIII detector is determined to be (10087Β±44)Γ106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
Using inclusive decays of the J/Ο, a precise determination of the number of J/Ο events collected with the BESIII detector is performed. For the two data sets taken in 2009 and 2012, the numbers of J/Ο events are recalculated to be (224.0Β±1.3)Γ106 and (1088.5Β±4.4)Γ106 respectively, which are in good agreement with the previous measurements. For the J/Ο sample taken in 2017--2019, the number of events is determined to be (8774.0Β±39.4)Γ106. The total number of J/Ο events collected with the BESIII detector is determined to be (10087Β±44)Γ106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
By analyzing an electron-positron collision data sample corresponding to an integrated luminosity of 2.93ββfbβ1 taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, we obtain for the first time the absolute branching fractions for seven π·0 and π·+ hadronic decay modes and search for the hadronic decay π·0βπΎ0πβ’πΎ0πβ’π0 with much improved sensitivity. The results are β¬β‘(π·0βπΎ0πβ’π0β’π0β’π0)=(7.64Β±0.30Β±0.29)Γ10β3, β‘(π·0βπΎββ’π+β’π0β’π0β’π0)=9.54Β±0.30Β±0.31)Γ10β3, β¬β‘(π·0βπΎ0πβ’π+β’πββ’π0β’π0)=(12.66Β±0.45Β±0.43)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π0β’π0)=(29.04Β±0.62Β±0.87)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π+β’πββ’π0)=(15.28Β±0.57Β±0.60)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π0β’π0β’π0)=(5.54Β±0.44Β±0.32)Γ10β3, β¬β‘(π·+βπΎββ’π+β’π+β’π0β’π0)=(4.95Β±0.26Β±0.19)Γ10β3, and β¬β‘(π·0βπΎ0πβ’πΎ0πβ’π0)<1.45Γ10β4 at the 90% confidence level. Here, the first uncertainties are statistical, and the second ones are systematic. The newly studied decays greatly enrich the knowledge of the π·βΒ―πΎβ’πβ’πβ’π and π·βΒ―πΎβ’πβ’πβ’πβ’π hadronic decays and open a bridge to access more two-body hadronic π· decays containing scalar, vector, axial, and tensor mesons in the charm sector.
The decays D β KβΟ+Ο+Οβ and D β KβΟ+Ο 0 are studied in a sample of quantum-correlated DDΒ― pairs produced through the process e+eβ β Ο(3770) β DDΒ―, exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fbβ1 . Here D indicates a quantum superposition of a D0 and a DΒ― 0 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 Ξ³ of the Unitarity Triangle in Bβ β DKβ decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3Ο = 0.52+0.12β0.10 and RKΟΟ0 = 0.78 Β± 0.04, with values for the average strong-phase differences that are Ξ΄ K3Ο D = (167+31β19)β¦ and Ξ΄KΟΟ0D = (196+14β15β¦ , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D β KβΟ+Ο+Οβ to yield results that will allow for a more sensitive measurement of Ξ³ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6β¦.