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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.
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%.
We report new measurements of the cross sections for the production of Dbar D final states at the Ο(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fbβ1 of e+eβ annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed Dbar D events ("double tags") to the yield of all reconstructed D or bar D mesons ("single tags") to determine the number of D0bar D0 and D+Dβ events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be Ο(e+eβ β D0bar D0) nb and Ο(e+eβ β D+Dβ) = (2.830 Β± 0.011 Β± 0.026) nb, where the uncertainties are statistical and systematic, respectively.
Using a data sample of π+β’πβ collisions corresponding to an integrated luminosity of 567ββpbβ1 collected at a center-of-mass energy of βπ =4.6ββGeV with the BESIII detector, we measure the absolute branching fraction of the inclusive semileptonic Ξ+π decay with a double-tag method. We obtain β¬β‘(Ξ+πβπβ’π+β’ππ)=(3.95Β±0.34Β±0.09)%, where the first uncertainty is statistical and the second systematic. Using the known Ξ+π lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons (π·0 and π·+), we obtain the ratio of the inclusive semileptonic decay widths Ξβ‘(Ξ+πβπβ’π+β’ππ)/Β―Ξβ‘(π·βπβ’π+β’ππ)=1.26Β±0.12.
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.
By analyzing a data sample corresponding to an integrated luminosity of 2.93ββfbβ1 collected at a center-of-mass energy of 3.773 GeV with By analyzing a data sample corresponding to an integrated luminosity of 2.93ββfbβ1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the absolute branching fraction of the π·+βπβ’π+β’ππ decay to be β¬π·+βπβ’π+β’ππ=(10.4Β±1.β’0statΒ±0.β’5syst)Γ10β4. Using the world averaged value of β¬π·+βπβ’π+β’ππ, the ratio of the two branching fractions is determined to be β¬π·+βπβ’π+β’ππ/β¬π·+βπβ’π+β’ππ=0.91Β±0.13(stat+syst), which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor ππ+β‘(0) and the πβπ Cabibbo-Kobayashi-Maskawa matrix element |ππβ’π| to be ππ+β‘(0)β’|ππβ’π|=0.087Β±0.00β’8statΒ±0.00β’2syst. Taking the input of |ππβ’π| from the global fit in the standard model, we determine ππ+β‘(0)=0.39Β±0.0β’4statΒ±0.0β’1syst. On the other hand, using the value of ππ+β‘(0) calculated in theory, we find |ππβ’π| = 0.242Β±0.02β’2statΒ±0.00β’6systΒ±0.03β’3theory.
We report the first observation of the semimuonic decay π·+βπβ’π+β’ππ using an π+β’πβ collision data sample corresponding to an integrated luminosity of 2.93ββfbβ1 collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the π·+βπβ’π+β’ππ decay is measured to be β¬π·+βπβ’π+β’ππ=(17.7Β±1.β’8statΒ±1.β’1syst)Γ10β4. Its ratio with the world average value of the branching fraction of the π·+βπβ’π+β’ππ decay probes lepton flavor universality and it is determined to be β¬π·+βπβ’π+β’ππ/β¬PDG π·+βπβ’π+β’ππ=1.05Β±0.14, in agreement with the standard model expectation within one standard deviation.