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Measurement of e⁺e⁻ → γχc0,c1,c2 cross sections at center-of-mass energies between 3.77 and 4.60 GeV
(2021)
The e+e−→γχcJ (J=0,1,2) processes are studied at center-of-mass energies ranging from 3.773 to 4.600 GeV, using a total integrated luminosity of 19.3 fb−1 e+e− annihilation data accumulated with the BESIII detector at BEPCII. We observe for the first time e+e−→γχc1,c2 signals at s√= 4.180 GeV with statistical significances of 7.6σ and 6.0σ, respectively. The production cross section of e+e−→γχc1,c2 at each center-of-mass energy is also measured. We find that the line shape of the e+e−→γχc1 cross section can be described with conventional charmonium states ψ(3686), ψ(3770), ψ(4040), ψ(4160). Compared with this, for the e+e−→γχc2 channel, one more additional resonance is added to describe the cross section line shape. Its mass and width are measured to be M=4371.7±7.5±1.8 MeV/c2 and Γtot=51.1±17.6±1.9 MeV, where the first uncertainties are statistical and the second systematic. The significance of this resonance is estimated to be 5.8σ, and its parameters agree with the Y(4360) resonance previously reported in e+e−→π+π−ψ(3686), and the Y(4390) in e+e−→π+π−hc within uncertainties. No significant signal for the e+e−→γχc0 process is observed, and the upper limits of Born cross sections σB(e+e−→γχc0) at 90\% confidence level are reported.
The Born cross section of the process e+e−→ΛΛ¯ is measured at 33 center-of-mass energies between 3.51 and 4.60 GeV using data corresponding to the total integrated luminosity of 20.0 fb−1 collected with the BESIII detector at the BEPCII collider. Describing the energy dependence of the cross section requires a contribution from the ψ(3770)→ΛΛ¯ decay, which is fitted with a significance of 4.6-4.9σ including the systematic uncertainty. The lower bound on its branching fraction is 2.4×10−6 at the 90% confidence level (C.L.), at least an order of magnitude larger than expected from predictions using a scaling based on observed electronic widths. This result indicates the importance of effects from vector charmonium(-like) states when interpreting data in terms of e.g., electromagnetic structure observables. The data do not allow for definite conclusions on the interplay with other vector charmonium(-like) states, and we set 90% C.L.upper limits for the products of their electronic widths and the branching fractions.
Using 2.93 fb−1 of e+e− collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays D0→K−e+νe and D+→K¯0e+νe to be (3.567±0.031stat±0.025syst)% and (8.68±0.14stat±0.16syst)%, respectively. Starting with the process e+e−→DD¯, a new reconstruction method is employed to select events that contain candidates for both D→K¯e+νe and D¯→Ke−ν¯e decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing D→K¯e+νe and hadronic D¯ decays. Combining our results with the lifetimes of the D0 and D+ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of Γ¯D0→K−e+νeΓ¯D+→K¯0e+νe=1.039±0.021. This ratio supports isospin symmetry in the D0→K−e+νe and D+→K¯0e+νe decays within 1.9σ.
Based on an 𝑒+𝑒− collision data sample corresponding to an integrated luminosity of 2.93 fb−1 collected with the BESIII detector at √𝑠=3.773 GeV, the first amplitude analysis of the singly Cabibbo-suppressed decay 𝐷+→𝐾+𝐾0𝑆𝜋0 is performed. From the amplitude analysis, the 𝐾*(892)+𝐾0𝑆 component is found to be dominant with a fraction of (57.1±2.6±4.2)%, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction ℬ(𝐷+→𝐾+𝐾0𝑆𝜋0) measured by BESIII, we obtain ℬ(𝐷+→𝐾*(892)+𝐾0𝑆)=(8.69±0.40±0.64±0.51)×10−3, where the third uncertainty is due to the branching fraction ℬ(𝐷+→𝐾+𝐾0𝑆𝜋0). The precision of this result is significantly improved compared to the previous measurement. This result also differs from most of theoretical predictions by about 4𝜎, which may help to improve the understanding of the dynamics behind.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44~GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
The Born cross section of the process e+e−→ΛΛ¯ is measured at 33 center-of-mass energies between 3.51 and 4.60 GeV using data corresponding to the total integrated luminosity of 20.0 fb−1 collected with the BESIII detector at the BEPCII collider. Describing the energy dependence of the cross section requires a justification from the ψ(3770)→ΛΛ¯ decay, which is fitted with a significance of 4.9σ with the systematic uncertainty included. The lower bound on its branching fraction is 2.4×10−6 at the 90\% confidence level (C.L.), at least five times larger than expected from predictions using a simple scaling approach. This result indicates the importance of effects from vector charmonium(-like) when interpreting data in terms of {\it e.g.}, electromagnetic structure observables. There are no definite conclusions about the interplay with other vector charmonium(-like), and we set 90\% C.L.upper limits for the products of the electronic widths and the branching fractions.
Using 2.93 fb−1 of e+e− collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays D0→K−e+νe and D+→K¯0e+νe to be (3.567±0.031stat±0.025syst)% and (8.68±0.14stat±0.16syst)%, respectively. Starting with the process e+e−→DD¯, a new reconstruction method is employed to select events that contain candidates for both D→K¯e+νe and D¯→Ke−ν¯e decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing D→K¯e+νe and hadronic D¯ decays. Combining our results with the lifetimes of the D0 and D+ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of Γ¯D0→K−e+νeΓ¯D+→K¯0e+νe=1.039±0.021. This ratio supports isospin symmetry in the D0→K−e+νe and D+→K¯0e+νe decays within 1.9σ.