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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.
Measurement of the cross section for eβΊeβ» β hadrons at energies from 2.2324 to 3.6710 GeV
(2022)
Based on electron-positron collision data collected with the BESIII detector operating at the Beijing Electron Positron Collider II storage rings, the value of Rβ‘Ο(e+eββhadrons)/Ο(e+eββΞΌ+ΞΌβ) is measured at 14 center-of-mass energies from 2.2324 to 3.6710 GeV. The resulting uncertainties are less than 3.0%, and are dominated by systematic uncertainties.
The decays of Οc2βK+KβΟ0, KSKΒ±Οβ and Ο+ΟβΟ0 are studied with the Ο(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of Οc2βKβKΒ―Β―Β―Β―Β―, Οc2βaΒ±2(1320)Οβ/a02(1320)Ο0 and Οc2βΟ(770)Β±Οβ are measured. Here KβKΒ―Β―Β―Β―Β― denotes both KβΒ±Kβ and Kβ0KΒ―Β―Β―Β―Β―0+c.c., and Kβ denotes the resonances Kβ(892), Kβ2(1430) and Kβ3(1780). The observations indicate a strong violation of the helicity selection rule in Οc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of Οc2βKβ(892)KΒ―Β―Β―Β―Β― are more than 10 times larger than the upper limit of Οc2βΟ(770)Β±Οβ, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
The decays of Οc2βK+KβΟ0, KSKΒ±Οβ and Ο+ΟβΟ0 are studied with the Ο(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of Οc2βKβKΒ―Β―Β―Β―Β―, Οc2βaΒ±2(1320)Οβ/a02(1320)Ο0 and Οc2βΟ(770)Β±Οβ are measured. Here KβKΒ―Β―Β―Β―Β― denotes both KβΒ±Kβ and Kβ0KΒ―Β―Β―Β―Β―0+c.c., and Kβ denotes the resonances Kβ(892), Kβ2(1430) and Kβ3(1780). The observations indicate a strong violation of the helicity selection rule in Οc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of Οc2βKβ(892)KΒ―Β―Β―Β―Β― are more than 20 times larger than that of Οc2βΟ(770)Β±Οβ, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The decays of Οc2βK+KβΟ0, KSKΒ±Οβ and Ο+ΟβΟ0 are studied with the Ο(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of Οc2βKβKΒ―Β―Β―Β―Β―, Οc2βaΒ±2(1320)Οβ/a02(1320)Ο0 and Οc2βΟ(770)Β±Οβ are measured. Here KβKΒ―Β―Β―Β―Β― denotes both KβΒ±Kβ and Kβ0KΒ―Β―Β―Β―Β―0+c.c., and Kβ denotes the resonances Kβ(892), Kβ2(1430) and Kβ3(1780). The observations indicate a strong violation of the helicity selection rule in Οc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of Οc2βKβ(892)KΒ―Β―Β―Β―Β― are more than 20 times larger than that of Οc2βΟ(770)Β±Οβ, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
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 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 0.165 β€ ma β€ 1.468GeV/c2.
The hadronic decay Ξ·c(2S)β3(Ο+Οβ) is observed with a statistical significance of 9.3 standard deviations using (448.1Β±2.9)Γ106 Ο(3686) events collected by the BESIII detector at the BEPCII collider. The measured mass and width of Ξ·c(2S) are (3643.4Β±2.3(stat.)Β±4.4(syst.)) MeV/c2 and (19.8Β±3.9(stat.)Β±3.1(syst.)) MeV, respectively, which are consistent with the world average values within two standard deviations. The product branching fraction B[Ο(3686) β Ξ³Ξ·c(2S)]ΓB[Ξ·c(2S)β3(Ο+Οβ)] is measured to be (9.2Β±1.0(stat.)Β±0.9(syst.))Γ10β6. Using B[Ο(3686)βΞ³Ξ·c(2S)]=(7.0+3.4β2.5)Γ10β4, we obtain B[Ξ·c(2S)β3(Ο+Οβ)]=(1.31Β±0.15(stat.)Β±0.13(syst.)(+0.64β0.47)(extr))Γ10β2, where the third uncertainty is from B[Ο(3686)βΞ³Ξ·c(2S)]. We also measure the ΟcJβ3(Ο+Οβ) (J=0,1,2) decays via Ο(3686)βΞ³ΟcJ transitions. The branching fractions are B[Οc0β3(Ο+Οβ)]=(2.080Β±0.006(stat.)Β±0.068(syst.))Γ10β2, B[Οc1β3(Ο+Οβ)]=(1.092Β±0.004(stat.)Β±0.035(syst.))Γ10β2, and B[Οc2β3(Ο+Οβ)]=(1.565Β±0.005(stat.)Β±0.048(syst.))Γ10β2.
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.
Using a sample of (10.09 Β± 0.04) Γ 109 J/Ο decays collected with the BESIII detector, partial wave analyses of the decay J/Ο β Ξ³K0SK0SΟ0 are performed within the K0SK0SΟ0 invariant mass region below 1.6 GeV/c2. The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the K0SK0 SΟ0 invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, i.e., the Ξ·(1405) with a mass of 1391.7Β±0.7+11.3 β0.3 MeV/c 2 and a width of 60.8Β±1.2+5.5 β12.0 MeV, and the Ξ·(1475) with a mass of 1507.6Β±1.6+15.5β32.2 MeV/c2 and a width of 115.8Β±2.4 +14.8 β10.9 MeV. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the K0SK0SΟ0invariant mass spectrum deteriorates significantly.