Abstract
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.Received 6 July 2021Accepted 13 September 2021DOI:https://doi.org/10.1103/PhysRevD.104.092001Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionHadron-hadron interactionsQuark modelParticles & Fields
Highlights
INTRODUCTIONMany charmoniumlike states were observed experimentally, such as the Xð3872Þ, Yð4260Þ, and Zcð3900Þ [1]
In the past decades, many charmoniumlike states were observed experimentally, such as the Xð3872Þ, Yð4260Þ, and Zcð3900Þ [1]
We find that the line shape of the eþe− → γχc1 cross section can be described with conventional charmonium states ψð3686Þ, ψð3770Þ, ψð4040Þ, ψð4160Þ
Summary
Many charmoniumlike states were observed experimentally, such as the Xð3872Þ, Yð4260Þ, and Zcð3900Þ [1]. Unlike the known 1−− conventional charmonium states that decay predominantly into open-charm final states [DðÃÞDðÃÞ], the Y-states show strong coupling to hidden-charm final states. By studying the radiative transitions between vector Y-states and χcJ (J 1⁄4 0, 1, 2), we can compare the decay of Y-states with conventional charmonium states, and help to understand the nature of Y states [13,14]. ΓχcJðJ 1⁄4 0; 1; 2Þ pprofficffi esses at eþe− center-of-mass (c.m.) energies between s 1⁄4 4.008–4.6 GeV, using data samples corresponding to an integrated luminosity of 16.0 fb−1 accumulated with the BESIII detector at the BEPCII collider. Compared with the previous BESIII measurement [15], the new dataset covers an extended c.m. energies with about one order of magnitude higher luminosity, and both J=ψ → eþe−=μþμ− events (only μþμ− used in previous work) are studied. The c.m. energy of each dataset is measured using dimuon events (eþe− → ðγÞμþμ−), with an uncertainty of Æ0.8 MeV [19]
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