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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.
Study of the eβΊeβ» β ΟβΊΟβ»Ο process at center-of-mass energies between 4.0 and 4.6 GeV
(2023)
Using 15.6 fbβ1 of e+eβ collision data collected at twenty-four center-of-mass energies from 4.0 to 4.6 GeV with the BESIII detector, the helicity amplitudes of the process e+eββΟ+ΟβΟ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5Ο are presented, such as f0(500), f0(980), f2(1270), f0(1370), b1(1235)Β±, and Ο(1450)Β±. In addition, evidence of a resonance state in e+eββΟ+ΟβΟ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/c2, which is consistent with the production of Ο(4160) or Y(4220).
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 a data sample of 448.1 Γ 106 Ο(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay Ο(3686) β Ξ· e+eβ, with significances of 7.0Ο and 6.3Ο when reconstructing the Ξ· meson via its decay modes Ξ· β Ξ³Ο+Οβ and Ξ· β Ο+ΟβΞ· (Ξ· β Ξ³Ξ³ ), respectively. The weighted average branching fraction is determined to be B(Ο(3686) β Ξ· e+eβ) = (1.90 Β± 0.25 Β± 0.11) Γ 10β6, where the first uncertainty is statistical and the second systematic.
Study of the eβΊeβ» β ΟβΊΟβ»Ο process at center-of-mass energies between 4.0 and 4.6 GeV
(2023)
Using 15.6 fbβ1 of e+eβ collision data collected at twenty-four center-of-mass energies from 4.0 to 4.6 GeV with the BESIII detector, the helicity amplitudes of the process e+eβ β Ο+ΟβΟ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5Ο are presented, such as f0(500), f0(980), f2(1270), f0(1370), b1(1235)Β±, and Ο(1450)Β±. In addition, evidence of a resonance state in e+eβ β Ο+ΟβΟ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/c2, which is consistent with the production of Ο(4160) or Y(4220).
We search for an axion-like particle (ALP) a through the process Ο(3686)βΟ+ΟβJ/Ο, J/ΟβΞ³a, aβΞ³Ξ³ in a data sample of (2.71Β±0.01)Γ109 Ο(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ΟβΞ³a and the ALP-photon coupling constant gaΞ³Ξ³ are set at 95% confidence level in the mass range of 0.165β€maβ€2.84GeV/c2. The limits on B(J/ΟβΞ³a) range from 8.3Γ10β8 to 1.8Γ10β6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165β€maβ€1.468GeV/c2.
We report the measurement of the cross sections for e+eββhadrons at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe a new resonance R(3810) in the cross sections for the first time, and observe the R(3760) resonance with high significance in the cross sections. The R(3810) has a mass of (3804.5Β±0.9Β±0.9) ~MeV/c2, a total width of (5.4Β±3.5Β±3.2)~MeV, and an electronic partial width of (19.4Β±7.4Β±12.1)~eV. Its significance is 7.7Ο. The R(3810) could be interpreted as a hadro-charmonium resonance predicted by Quantum Chromodynamics (QCD). In addition, we measure the mass (3751.9Β±3.8Β±2.8) ~MeV/c2, the total width (32.8Β±5.8Β±8.7)~MeV, and the electronic partial width (184Β±75Β±86)~eV with improved precision for the R(3760). Furthermore, for the R(3780) we measure the mass (3778.7Β±0.5Β±0.3) ~MeV/c2 and total width (20.3Β±0.8Β±1.7)~MeV with improved precision, and the electronic partial width (265Β±69Β±83)~eV. The R(3780) can be interpreted as the 13D1 state of charmonium. Its mass and total width differ significantly from the corresponding fitted values given by the Particle Data Group in 2022 by 7.1 and 3.2 times the uncertainties for Ο(3770), respectively. Ο(3770) has been interpreted as the 13D1 state for 45 years.
We search for an axion-like particle (ALP) a through the process Ο(3686)βΟ+ΟβJ/Ο, J/ΟβΞ³a, aβΞ³Ξ³ in a data sample of (2.71Β±0.01)Γ109 Ο(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ΟβΞ³a and the ALP-photon coupling constant gaΞ³Ξ³ are set at 95% confidence level in the mass range of 0.165β€maβ€2.84GeV/c2. The limits on B(J/ΟβΞ³a) range from 8.3Γ10β8 to 1.8Γ10β6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165β€maβ€1.468GeV/c2.
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.