Evidence of a Broad Structure at an Invariant Mass of4.32  GeV/c2in the Reactione+e−

Abstract

We present a measurement of the cross section of the process e(+)e(-)-->pi(+)pi(-)psi(2S) from threshold up to 8 GeV center-of-mass energy using events containing initial-state radiation, produced at the SLAC PEP-II e(+)e(-) storage rings. The study is based on 298 fb(-1) of data recorded with the BABAR detector. A structure is observed in the cross section not far above threshold, near 4.32 GeV. We also investigate the compatibility of this structure with the Y(4260) previously reported by this experiment.

The hidden-charm pentaquark and tetraquark states

“…After the observation of the Y(4260) in e + e − → γ ISR π + π − J/ψ, the BaBar Collaboration analyzed a similar process e + e − → γ ISR π + π − ψ(3686), where a resonant structure Y(4360) was observed [144]. Later, the Belle Collaboration confirmed the existence of the Y(4360) in the same process.…”

“…For the Y(4360) and Y(4660), only the ψ(3686)π + π − decay mode was observed [144,145,146]. Their open charm decay modes such as Y(4360)/Y(4660) → D 0 D * − π + are still missing [128].…”

“…Belle's observation of the Y(4660) [145] was not confirmed by BaBar [144], which resulted in a long-term debate whether there is a Y(4660) structure in e + e − → γ ISR π + π − ψ(3686). Finally in 2012, BaBar confirmed the existence of the Y(4660) with new data on the e + e − → γ ISR π + π − ψ(3686) process [146].…”

“…The measured π + π − ψ(2S ) invariant mass spectrum of e + e − → γ ISR π + π − ψ(2S ) from BaBar and Belle. Here, the upper left and lower left panels are taken from BaBar [144,146], and the upper right panel is taken from Belle [145]. The lower right panel is a comparison of the Belle (dots with errors) and BaBar (hatched histogram) data from BaBar [146].…”

Observation of e+e−→ϕχc1 and ϕχ

“…The Xð3872Þ was first observed by the Belle Collaboration in B AE → K AE π þ π − J/ψ [1] and was subsequently confirmed by several other experiments [2][3][4][5]. The vector states Xð4260Þ, Xð4360Þ, and Xð4660Þ, sometimes called the Yð4260Þ, Yð4360Þ, and Yð4660Þ, were discovered by the BABAR, Belle, and CLEO collaborations via their decays into low-mass charmonium states π þ π − J/ψ or π þ π − ψð3686Þ [6][7][8][9][10]. Some charged charmonium-like states and their neutral partners, such as Z c ð3900Þ, Z c ð3885Þ, Z c ð4020Þ, Z c ð4025Þ, Z c ð4200Þ have been also observed by several experiments [11][12][13][14][15][16][17][18][19][20][21].…”