Abstract
We study ηc production at center-of-mass energies s from 4.18 to 4.60 GeV in e+e− annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to 7.3 fb−1 of integrated luminosity. We measure the cross sections of the three different exclusive reactions e+e−→ηcπ+π−π0, e+e−→ηcπ+π−, and e+e−→ηcπ0γ. We find significant ηc production in e+e−→ηcπ+π−π0 at s of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate Y(4260) resonance. In addition, we perform a search for a charmoniumlike Zc state close to the DD¯ threshold that decays to ηcπ, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of ηc and Zc production are provided, where the yields are not found to be significant.2 MoreReceived 28 October 2020Accepted 6 January 2021DOI:https://doi.org/10.1103/PhysRevD.103.032006Published 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 AreasHadronic decaysPhysical SystemsCharmed mesonsExotic mesonsHadronsMesonsParticles & Fields
Highlights
A series of new, unexpected states have been observed at eþe− colliders in studies dating back to the beginning of the millennium
For the upper limits on the Born cross sections σBorn, the systematic uncertainties are taken into account by convolving the likelihood distributions (Fig. 4) with a Gaussian of standard deviation σsys;total, which broadens them, leading to correspondingly more conservative UL90 values
To take into account the systematic uncertainties in the signal significances Stot, again the likelihood distributions are convolved with a Gaussian with width set to the standard deviation that corresponds to the relevant systematic uncertainty
Summary
A series of new, unexpected states have been observed at eþe− colliders in studies dating back to the beginning of the millennium. In the case of significant ηc production cross sections, further insight will come from the subsequent search for possible Zc-like states close to the open-charm threshold, decaying to ηcπ, First evidence of more than 3σ significance for a charged charmoniumlike ηcπ resonance with a mass of mZ−c 1⁄4 ð4096 Æ 20þ−2128Þ MeV=c2 and a width of ΓZ−c 1⁄4 ð152 Æ 58þ−3650Þ MeV has been reported in B0 → Kþηcπ− decays by the LHCb Collaboration [31].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
