Observation of the Y(4230) and a new structure in *

Abstract

The cross sections of $e^+e^- \rightarrow K^+K^-J/\psi$ at center-of-mass energies from 4.127 to 4.600~GeV are measured based on 15.6 fb$^{-1}$ data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in the line shape of the cross sections. The mass and width of the first structure are measured to be ($4225.3\pm2.3\pm21.5$) MeV and ($72.9\pm6.1\pm30.8$)~MeV, respectively. They are consistent with those of the established $Y(4230)$. The second structure is observed for the first time with a statistical significance greater than 8$\sigma$, denoted as $Y(4500)$. Its mass and width are determined to be ($4484.7\pm13.3\pm24.1$) MeV and ($111.1\pm30.1\pm15.2$) MeV, respectively. The first presented uncertainties are statistical and the second ones are systematic. The product of the electronic partial width with the decay branching fraction $ \Gamma(Y(4230)\to e^+ e^-) \mathcal{B}(Y(4230) \to K^+ K^- J/\psi)$ is reported.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Observation of a Charged Charmoniumlike Structure in e+e−→π+π−J/ψ at s=4.26 GeV

“…MeV, respectively, which are consistent with that of Ref. [59]. The mass and width of the third structure, denoted as Y (4710), are M 3 = 4708 +17 −15 MeV/c 2 and Γ 3 = 126 +27 −23 MeV, respectively.…”

“…Fitting the cross sections from this work and Ref. [59] with three resonances (Y (4230), Y (4500), and Y (4710)), we obtain the mass and width of the Y (4710) to be M (4710) = 4708 +17 −15 ± 21 MeV/c 2 and Γ(4710) = 126 +27 −23 ± 30 MeV, where the first uncertainties are statistical and the second systematic. A new resonance structure Y (4710) is observed with a statistical significance over 5σ, which is one of the heaviest vector charmoniumlike states.…”

“…energies from 4.61 to 4.95 GeV [57], corresponding to an integrated luminosity of 5.85 fb −1 [58]. Compared with a previous measurement [59], new data above 4.6 GeV is analyzed for the first time, which enables us to investigate the Y states above 4.6 GeV with improved precision [60,61]. To achieve much lower background levels and to improve the statistics, both full reconstruction and partial reconstruction methods are applied.…”

“…To determine the parameters of the structures, a maximum likelihood method is used to fit the dressed cross sections obtained in this work and the dressed cross sections with √ s < 4.61 GeV [59]. The likelihood is constructed taking into consideration the fluctuations of the numbers of signal and background events.…”

Bottomoniumlike tetraquarks in a chiral quark model

“…The masses of these exotic states are generally located near particular thresholds of two conventional open-heavyflavor mesons. Examples of this fact are the charged charmonium-like states with strangeness X 0,1 (2900) [5,6], X(2600) [7], Z cs (3985) [8], Z cs (4000), Z cs (4220), X(4630) and X(4685) [9]; the hidden charm structures ψ 2 (3823) [10,11] and X(3960) [12]; the charmoniumlike vector meson states Y (4230), Y (4500), Y (4660) and Y (4710) [13][14][15]; and the J/ψ-J/ψ bound-state candidates [16].…”