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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.
We measure the inclusive semielectronic decay branching fraction of the D+s meson. A double-tag technique is applied to e+eβ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range 4.178β4.230 GeV. We select positrons fromD+sβXe+Ξ½e with momenta greater than 200 MeV/c and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the D+s semielectronic branching fraction to be(6.30Β±0.13(stat.)Β±0.09(syst.)Β±0.04(ext.))%, showing no evidence for unobserved exclusive semielectronic modes. We combine this result with external data taken from literature to determine the ratio of the D+s and D0 semielectronic widths, Ξ(D+sβXe+Ξ½e)Ξ(D0βXe+Ξ½e)=0.790Β±0.016(stat.)Β±0.011(syst.)Β±0.016(ext.). Our results are consistent with and more precise than previous measurements.
Using 10.1 Γ 109 J/Ο events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy βs = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/Ο β Dβe+Ξ½e + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction B(J/Ο β Dβe +Ξ½e + c.c.) < 7.1 Γ 10β8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
Based on an e+eβ collision data sample corresponding to an integrated luminosity of 2.93 fbβ1 collected with the BESIII detector at βs=3.773 GeV, the first amplitude analysis of the singly Cabibbo-suppressed decay D+βK+K0SΟ0 is performed. From the amplitude analysis, the Kβ(892)+K0S component is found to be dominant with a fraction of (57.1Β±2.6Β±4.2)%, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction B(D+βK+K0SΟ0) measured by BESIII, we obtain B(D+βKβ(892)+K0S)=(8.69Β±0.40Β±0.64Β±0.51)Γ10β3, where the third uncertainty is due to the branching fraction B(D+βK+K0SΟ0). The precision of this result is significantly improved compared to the previous measurement. This result also differs from most of theoretical predictions by about 4Ο, which may help to improve the understanding of the dynamics behind.
Using 2.93 fbβ1 of e+eβ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0βK1(1270)βe+Ξ½e semileptonic decay is presented. The statistical significance of the decay D0βK1(1270)βe+Ξ½e is greater than 10Ο. The branching fraction of D0βK1(1270)βe+Ξ½e is measured to be (1.09Β±0.13+0.09β0.13Β±0.12)Γ10β3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)ββKβΟ+Οβ.
Using 2.93 fbβ1 of e+eβ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0βK1(1270)βe+Ξ½e semileptonic decay is presented. The statistical significance of the decay D0βK1(1270)βe+Ξ½e is greater than 10Ο. The branching fraction of D0βK1(1270)βe+Ξ½e is measured to be (1.09Β±0.13+0.09β0.16Β±0.12)Γ10β3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)ββKβΟ+Οβ. The fraction of longitudinal polarization in D0βK1(1270)βe+Ξ½e is determined for the first time to be 0.50Β±0.19statΒ±0.08syst.
Using a data sample of (1310.6Β±7.0)Γ106ββπ½/π events taken with the BESIII detector at the center-of-mass energy of 3.097 GeV, we search for the first time for the lepton number violating decay Ξ£ββπβ’πββ’πβ and the rare inclusive decay Ξ£ββΞ£+β’π, where π denotes any possible particle combination. The Ξ£β candidates are tagged in π½/πβΒ―Ξ£β’(1385)+β’Ξ£β decays. No signal candidates are found, and the upper limits on the branching fractions at the 90% confidence level are determined to be β¬β‘(Ξ£ββπβ’πββ’πβ)<6.7Γ10β5 and β¬β‘(Ξ£ββΞ£+β’π)<1.2Γ10β4.
Cross section measurement of eβΊeβ» β ΟβΊΟβ»Ο(3686) from βs = 4.0076 GeV to 4.6984 GeV
(2021)
Using data samples with a total integrated luminosity of 20.1ββfbβ1 collected by the BESIII detector operating at the BEPCII collider, the cross section of the process π+β’πββπ+β’πββ’πβ‘(3686) is measured at center-of-mass energies between 4.0076 and 4.6984 GeV. The measured cross section is consistent with previous results, and with much improved precision. A fit to the measured energy-dependent cross section, which includes three Breit-Wigner functions and a nonresonant contribution, confirms the existence of the charmonium-like states πβ‘(4220), πβ‘(4390), and πβ‘(4660). This is the first observation of the πβ‘(4660) at the BESIII experiment.
Using a total of 5.25 fbβ1 of e+eβ collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process e+eβ β Ξ·Ο(2S) with a statistical significance of 4.9 standard deviations. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.
We report new measurements of the branching fraction β¬β‘(π·+π ββ+β’π), where β+ is either π+ or π+β‘(βπ+β’Β―ππ), based on 6.32ββfbβ1 of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between 4.178 and 4.226 GeV. Simultaneously floating the π·+π βπ+β’ππ and π·+π βπ+β’ππ components yields β¬β‘(π·+π βπ+β’ππ)=(5.21Β±0.25Β±0.17)Γ10β2, β¬β‘(π·+π βπ+β’ππ)=(5.35Β±0.13Β±0.16)Γ10β3, and the ratio of decay widths π
=Ξβ‘(π·+π βπ+β’ππ)Ξβ‘(π·+π βπ+β’ππ)=9.7β’3+0.61β0.58Β±0.36, where the first uncertainties are statistical and the second systematic. No evidence of πΆβ’π asymmetry is observed in the decay rates π·Β±π βπΒ±β’ππ and π·Β±π βπΒ±β’ππ: π΄πΆβ’πβ‘(πΒ±β’π)=(β1.2Β±2.5Β±1.0)% and π΄πΆβ’πβ‘(πΒ±β’π)=(+2.9Β±4.8Β±1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (π
=9.75), we find the more precise results β¬β‘(π·+π βπ+β’ππ)=(5.22Β±0.10Β±0.14)Γ10β2 and π΄πΆβ’πβ‘(πΒ±β’ππ)=(β0.1Β±1.9Β±1.0)%. Combining our results with inputs external to our analysis, we determine the πβΒ―π quark mixing matrix element, π·+π decay constant, and ratio of the decay constants to be |ππβ’π |=0.973Β±0.009Β±0.014, ππ·+π =249.9Β±2.4Β±3.5ββMeV, and ππ·+π /ππ·+=1.232Β±0.035, respectively.