Combined fit to the \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) line shape

The European Physical Journal C, Oct 2017

We analyze the cross section of \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) measured by Belle, BABAR and BESIII experiments. The parameters of the two resonances Y(4220) and Y(4360) are consistent with that in \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\). A combined fit is performed to the two cross sections assuming the two resonances Y(4220) and Y(4360) have the same parameters. The parameters of Y(4220), Y(4360) and Y(4660) are determined to be \(M_{Y(4220)}=(4223.3\pm 1.6\pm 2.5)\) MeV/c\(^{2}\), \(\Gamma _{Y(4220)}=(54.2\pm 2.6\pm 1.0)\) MeV; \(M_{Y(4360)}=(4386.4\pm 2.1\pm 6.4)\) MeV/c\(^{2}\), \(\Gamma _{Y(4360)}=(96.0\pm 6.7\pm 2.7)\) MeV; \(M_{Y(4660)}=(4646.4\pm 9.7\pm 4.8)\) MeV/c\(^{2}\), \(\Gamma _{Y(4660)}=(103.5\pm 15.6\pm 4.0)\) MeV, where the first uncertainties are statistical and the second systematic. The ratios \(\frac{\mathcal {B}(Y(4220) \rightarrow \pi ^{+}\pi ^{-}\psi (3686))}{\mathcal {B}(Y(4220) \rightarrow \pi ^{+}\pi ^{-}J/\psi )}\) and \(\frac{\mathcal {B}(Y(4360) \rightarrow \pi ^{+}\pi ^{-}\psi (3686))}{\mathcal {B}(Y(4360) \rightarrow \pi ^{+}\pi ^{-}J/\psi )}\) are also obtained, which may help in understanding the nature of these structures.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1140%2Fepjc%2Fs10052-017-5328-1.pdf

Combined fit to the \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) line shape

The European Physical Journal C November 2017, 77:727 | Cite as Combined fit to the \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) line shape AuthorsAuthors and affiliations Jielei ZhangLimin Yuan Open Access Regular Article - Theoretical Physics First Online: 31 October 2017 368 Downloads 1 Citations Abstract We analyze the cross section of \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) measured by Belle, BABAR and BESIII experiments. The parameters of the two resonances Y(4220) and Y(4360) are consistent with that in \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\). A combined fit is performed to the two cross sections assuming the two resonances Y(4220) and Y(4360) have the same parameters. The parameters of Y(4220), Y(4360) and Y(4660) are determined to be \(M_{Y(4220)}=(4223.3\pm 1.6\pm 2.5)\) MeV/c\(^{2}\), \(\Gamma _{Y(4220)}=(54.2\pm 2.6\pm 1.0)\) MeV; \(M_{Y(4360)}=(4386.4\pm 2.1\pm 6.4)\) MeV/c\(^{2}\), \(\Gamma _{Y(4360)}=(96.0\pm 6.7\pm 2.7)\) MeV; \(M_{Y(4660)}=(4646.4\pm 9.7\pm 4.8)\) MeV/c\(^{2}\), \(\Gamma _{Y(4660)}=(103.5\pm 15.6\pm 4.0)\) MeV, where the first uncertainties are statistical and the second systematic. The ratios \(\frac{\mathcal {B}(Y(4220) \rightarrow \pi ^{+}\pi ^{-}\psi (3686))}{\mathcal {B}(Y(4220) \rightarrow \pi ^{+}\pi ^{-}J/\psi )}\) and \(\frac{\mathcal {B}(Y(4360) \rightarrow \pi ^{+}\pi ^{-}\psi (3686))}{\mathcal {B}(Y(4360) \rightarrow \pi ^{+}\pi ^{-}J/\psi )}\) are also obtained, which may help in understanding the nature of these structures. In recent years, charmonium physics has gained renewed strong interest from both the theoretical and the experimental side, due to the observation of a dozen of charmonium-like states, such as X(3872) [1, 2], Y(4260) [3, 4, 5], Y(4360) [6, 7] and Y(4660) [7]. These states do not fit in the conventional charmonium spectroscopy, and they are good candidates for exotic states beyond the quark model [8]. Among them, the vector charmonium-like states, having quantum numbers \(J^{PC}=1^{--}\), are usually called Y-states. The first observed Y-state is Y(4260), which was seen by BABAR [3] in the \(\pi ^{+}\pi ^{-}J/\psi \) mass distribution through initial-state-radiation (ISR) process, then confirmed by CLEO [4] and Belle [5] experiments. With high statistic data, BESIII experiment observed the fine structure for Y(4260) in \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) [9]. The Y(4260) is a combination of two resonances, the lower one’s mass is around 4.22 GeV/\(c^2\) and the higher one’s mass is around 4.32 GeV/\(c^2\). The resonance Y(4220) also is observed in some other decay channels at BESIII, such as \(e^+e^-\rightarrow \omega \chi _{c0}\) [10, 11], \(\pi ^{+}\pi ^{-}h_{c}\) [12, 13] and \(\pi ^{+}D^{0}D^{*-}\) [14]. Another famous Y-state Y(4360) was firstly observed by BABAR [6] in \(\pi ^{+}\pi ^{-}\psi (3686)\) mass distribution, then confirmed by Belle [7] experiment. Belle also observed another structure, Y(4660), in the \(\pi ^{+}\pi ^{-}\psi (3686)\) [7]. Recently, using the results for \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) from Belle [15], BABAR [16] and BESIII [17] experiments, the authors of Ref. [18] observed the fine structure for Y(4360) in \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\), inferring that also the Y(4360) is a combination of two resonances, the lower one’s mass is around 4.22 GeV/\(c^2\) and the higher is around 4.38 GeV/\(c^2\). There are many theoretical models to explain these Y-states, such as hybrid charmonium, tetraquark state and the molecular state [19]. However, there is still no definite conclusion. On the other hand, there are still missing excited charmonium states predicted by the potential models, which we have not observed. So it is important to confirm which Y-states are charmonium and which Y-states are exotic states. In this paper, we revisit the \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) line shape, and we perform a combined fit to the two cross sections \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\). These results will be useful in understanding the nature of charmonium(-like) states in this energy region. The cross section measurements for process \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) have been improved by Belle [20], BABAR [21] and BESIII [9] experiments, especially the BESIII results with very high precision. Figure 1 (left) shows the cross sections from the three experiments for the \(e^+e^-\) center-of-mass energy, \(\sqrt{s}\), from 3.8 to 4.6 GeV, and they are consistent with each other within error. The \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) cross section also has been measured by Belle [15], BABAR [16] and BESIII [17] experiments. Figure 1 (right) shows the results for \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\). The cross section of \ (...truncated)


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1140%2Fepjc%2Fs10052-017-5328-1.pdf

Jielei Zhang, Limin Yuan. Combined fit to the \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}J/\psi \) and \(e^+e^-\rightarrow \pi ^{+}\pi ^{-}\psi (3686)\) line shape, The European Physical Journal C, 2017, pp. 727, Volume 77, Issue 11, DOI: 10.1140/epjc/s10052-017-5328-1