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Using (10087±44)×106 J/ψ events collected with the BESIII detector, the radiative hyperon decay Σ→pγ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be (0.996±0.021stat.±0.018syst.)×10−3, which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be −0.652±0.056stat.±0.020syst.. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.
Using (10087±44)×106 J/ψ events collected with the BESIII detector, the radiative hyperon decay Σ→pγ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be (0.996±0.021stat.±0.018syst.)×10−3, which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be −0.652±0.056stat.±0.020syst.. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.
Using (10087±44)×106 J/ψ events collected with the BESIII detector, the radiative hyperon decay Σ→pγ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be (0.996±0.021stat.±0.018syst.)×10−3, which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be −0.652±0.056stat.±0.020syst.. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.
Based on e+e− collision samples corresponding to an integrated luminosity of 4.4 fb−1 collected with the BESIII detector at center-of-mass energies between 4.6GeV and 4.7GeV, a partial wave analysis of the charmed baryon hadronic decay Λ+c→Λπ+π0 is performed, and the decays Λ+c→Λρ(770)+ and Λ+c→Σ(1385)π are studied for the first time. Making use of the world-average branching fraction B(Λ+c→Λπ+π0), their branching fractions are determined to be B(Λ+c→Λρ(770)+)=B(Λ+c→Σ(1385)+π0)=B(Λ+c→Σ(1385)0π+)=(4.06±0.30±0.35±0.23)×10−2,(5.86±0.49±0.52±0.35)×10−3,(6.47±0.59±0.66±0.38)×10−3, where the first uncertainties are statistical, the second are systematic, and the third are from the uncertainties of the branching fractions B(Λ+c→Λπ+π0) and B(Σ(1385)→Λπ). In addition, %according to amplitudes determined from the partial wave analysis, the decay asymmetry parameters are measured to be αΛρ(770)+=−0.763±0.053±0.039, αΣ(1385)+π0=−0.917±0.069±0.046, and αΣ(1385)0π+=−0.789±0.098±0.056.
Using a data set of electron-positron collisions corresponding to an integrated luminosity of 2.93 fb−1 taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, a search for the baryon (B) and lepton (L) number violating decays D±→n(n¯)e± is performed. No signal is observed and the upper limits on the branching fractions at the 90% confidence level are set to be 1.43×10−5 for the decays D+(−)→n¯(n)e+(−) with Δ|B−L|=0, and 2.91×10−5 for the decays D+(−)→n(n¯)e+(−) with Δ|B−L|=2 , where Δ|B−L| denotes the change in the difference between baryon and lepton numbers.
Using a data set of electron-positron collisions corresponding to an integrated luminosity of 2.93 fb−1 taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, a search for the baryon (B) and lepton (L) number violating decays D±→n(n¯)e± is performed. No signal is observed and the upper limits on the branching fractions at the 90% confidence level are set to be 1.43×10−5 for the decays D+(−)→n¯(n)e+(−) with Δ|B−L|=0, and 2.91×10−5 for the decays D+(−)→n(n¯)e+(−) with Δ|B−L|=2 , where Δ|B−L| denotes the change in the difference between baryon and lepton numbers.
Using a data set of electron-positron collisions corresponding to an integrated luminosity of 2.93 fb−1 taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, a search for the baryon (B) and lepton (L) number violating decays D±→n(n¯)e± is performed. No signal is observed and the upper limits on the branching fractions at the 90% confidence level are set to be 1.43×10−5 for the decays D+(−)→n¯(n)e+(−) with Δ|B−L|=0, and 2.91×10−5 for the decays D+(−)→n(n¯)e+(−) with Δ|B−L|=2 , where Δ|B−L| denotes the change in the difference between baryon and lepton numbers.
Using a sample of 4.3×105 η′→ηπ0π0 events selected from the ten billion J/ψ event dataset collected with the BESIII detector, we study the decay η′→ηπ0π0 within the framework of nonrelativistic effective field theory. Evidence for a structure at π+π− mass threshold is observed in the invariant mass spectrum of π0π0 with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a0−a2 is determined to be 0.226±0.060stat±0.013syst, which is in good agreement with theoretical calculation of 0.2644±0.0051.
Using a sample of 4.3×105 η′→ηπ0π0 events selected from the 10 billion J/ψ event data set collected with the BESIII detector, we study the decay η′→ηπ0π0 within the framework of non-relativistic effective field theory. Evidence for a structure at π+π− mass threshold is observed in the invariant mass spectrum of π0π0 with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the non-relativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a0−a2 is determined to be 0.226±0.060stat.±0.012syst., which is in good agreement with theoretical calculation of 0.2644±0.0051.
Using a sample of 4.3×105 η′→ηπ0π0 events selected from the ten billion J/ψ event dataset collected with the BESIII detector, we study the decay η′→ηπ0π0 within the framework of nonrelativistic effective field theory. Evidence for a structure at π+π− mass threshold is observed in the invariant mass spectrum of π0π0 with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a0−a2 is determined to be 0.226±0.060stat±0.013syst, which is in good agreement with theoretical calculation of 0.2644±0.0051.