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Institute
The polarization of Ξ and ΞΒ― hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at βsNN = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.
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.
Born cross sections for the processes e+eβ β ΟΞ· and e+eβ β ΟΟ0 have been determined for centerof-mass energies between 2.00 and 3.08 GeV with the BESIII detector at the BEPCII collider. The results obtained in this work are consistent with previous measurements but with improved precision. Two resonant structures are observed. In the e+eβ β ΟΞ· cross sections, a resonance with a mass of (2176 Β± 24 Β± 3) MeV/c2 and a width of (89 Β± 50 Β± 5) MeV is observed with a significance of 6.2Ο. Its properties are consistent with the Ο(2170). In the e+eβ β ΟΟ0 cross sections, a resonance denoted Y (2040) is observed with a significance of more than 10Ο. Its mass and width are determined to be (2034 Β± 13 Β± 9) MeV/c2 and (234 Β± 30 Β± 25) MeV, respectively, where the first uncertainties are statistical and the second ones are systematic.
We report an amplitude analysis and branching fraction measurement of D+sβK+KβΟ+ decay using a data sample of 3.19 fbβ1 recorded with BESIII detector at a center-of-mass energy of 4.178 GeV.
We perform a model-independent partial wave analysis in the low K+Kβ mass region to determine the K+Kβ S-wave lineshape, followed by an amplitude analysis of our very pure high-statistics sample.
The amplitude analysis provides an accurate determination of the detection efficiency allowing us to measure the branching fraction B(D+sβK+KβΟ+)=(5.47Β±0.08statΒ±0.13sys)%.
We report an amplitude analysis and branching fraction measurement of D+sβK+KβΟ+ decay using a data sample of 3.19 fbβ1 recorded with BESIII detector at a center-of-mass energy of 4.178 GeV.
We perform a model-independent partial wave analysis in the low K+Kβ mass region to determine the K+Kβ S-wave lineshape, followed by an amplitude analysis of our very pure high-statistics sample.
The amplitude analysis provides an accurate determination of the detection efficiency allowing us to measure the branching fraction B(D+sβK+KβΟ+)=(5.47Β±0.08statΒ±0.13sys)%.
We report an amplitude analysis and branching fraction measurement of D+sβK+KβΟ+ decay using a data sample of 3.19 fbβ1 recorded with BESIII detector at a center-of-mass energy of 4.178 GeV.
We perform a model-independent partial wave analysis in the low K+Kβ mass region to determine the K+Kβ S-wave lineshape,
followed by an amplitude analysis of our very pure high-statistics sample.
The amplitude analysis provides an accurate determination of the detection efficiency allowing us to measure the branching fraction B(D+sβK+KβΟ+)=(5.47Β±0.08statΒ±0.13sys)%.
Using 2.93ββfbβ1 of π+β’πβ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay π·+βπΎ+β’π+β’πββ’π0 is reported. After removing decays that contain narrow intermediate resonances, including π·+βπΎ+β’π, π·+βπΎ+β’π, and π·+βπΎ+β’π, the branching fraction of the decay π·+βπΎ+β’π+β’πββ’π0 is measured to be (1.13Β±0.0β’8statΒ±0.0β’3syst)Γ10β3. The ratio of branching fractions of π·+βπΎ+β’π+β’πββ’π0 over π·+βπΎββ’π+β’π+β’π0 is found to be (1.81Β±0.15)%, which corresponds to (6.28Β±0.52)β’tan4β‘ππΆ, where ππΆ is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays π·Β±βπΎΒ±β’πΒ±β’πββ’π0 is also determined, and no evidence for πΆβ’π violation is found. In addition, the first evidence for the π·+βπΎ+β’π decay, with a statistical significance of 3.3β’π, is presented and the branching fraction is measured to be β¬β‘(π·+βπΎ+β’π) = (5.β’7+2.5β2.1statΒ±0.β’2syst)Γ10β5.
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.
Study of the process eβΊeβ»βββΟβ°Οβ°J/Ο and neutral charmoniumlike state Zc(3900)β°
(2020)
Cross sections of the process π+β’πββπ0β’π0β’π½/π at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4ββfbβ1 of data samples collected with the BESIII detector operating at the BEPCII collider facility. A fit to the measured energy-dependent cross sections confirms the existence of the charmoniumlike state πβ‘(4220). The mass and width of the πβ‘(4220) are determined to be (4220.4Β±2.4Β±2.3) MeV/π2 and (46.2Β±4.7Β±2.1)ββMeV, respectively, where the first uncertainties are statistical and the second systematic. The mass and width are consistent with those measured in the process π+β’πββπ+β’πββ’π½/π. The neutral charmonium-like state ππβ’(3900)0 is observed prominently in the π0β’π½/π invariant-mass spectrum, and, for the first time, an amplitude analysis is performed to study its properties. The spin-parity of ππβ’(3900)0 is determined to be π½π=1+, and the pole position is (3893.1Β±2.2Β±3.0)βπβ’(22.2Β±2.6Β±7.0)ββMeV/π2, which is consistent with previous studies of electrically charged ππβ’(3900)Β±. In addition, cross sections of π+β’πβ β π0β’ππβ’(3900)0 β π0β’π0β’π½/π are extracted, and the corresponding line shape is found to agree with that of the πβ‘(4220).
The process π+β’πββπβ’πβ² has been studied for the first time in detail using data sample collected with the BESIII detector at the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A resonance with quantum numbers π½πβ’πΆ=1ββ is observed with mass π=(2177.5Β±4.8β’(stat)Β±19.5β’(syst))β’MeV/π2 and width Ξ=(149.0Β±15.6β’(stat)Β±8.9β’(syst))ββMeV with a statistical significance larger than 10β’π, including systematic uncertainties. If the observed structure is identified with the πβ‘(2170), then the ratio of partial width between the πβ’πβ² by BESIII and πβ’π by BABAR is (β¬π
πβ’πβ’Ξπ
πβ’π)/(β¬π
πβ’πβ²β’Ξπ
πβ’π)=0.23Β±0.10β’(stat)Β±0.18β’(syst), which is smaller than the prediction of the π β’Β―π β’π hybrid models by several orders of magnitude.