| Many exotic charmonium-like states have been discovered above open charm threshold,such as Y(4260),Y(4360)and Y(4660),which are poorly understood theoretically.These new charmoniumlike vector states(Y states)have been observed in e+e-annihilation directly or via the initial state ra-diation process,and decay in dipion hadronic transitions to the lower char-monium J/? or ?(2S).Searching for new modes in e+e-annihilation and measuring the line shapes of the production cross sections will be very help-ful for interpreting these exotic charmonium-like states,even discovering new particles.We search for the coupling of excited ? and Y states couple to ??(2S),and measure the cross section of e+e-???(2S).CLEO-c experiment searched for this process with data at center-of-mass energy(?)= 4.260 GeV,and did not observe any signal.The process e+e-???(2S)is ob-served for the first time using e+e-collision data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.236 to 4.600 GeV.The statistical significance of the signal in the full 5.2 fb-1 data sample is 5.5??The cross sections at center mass energies 4.258 and 4.267 GeV are measured to be(1.82-0.77-1.17±0.23)and(3.13-1.54+1.86±0.33)pb,respectively,where the first uncertainties are statistical and the second systematic.Here,the corresponding statistical significances are 3.4a and 3.2?.Due to the limitation of statistics at some energy point,upper limit of the Born cross section is provided at 90%confidence level,for the energy point where the signal is not evident.We fit the cross section line shape of process e+e-???(2S)and find the evidence of Y(4260).The mass and width of Y(4260)are(4262.9± 6.6)MeV/c2 and(30.0± 10.0)MeV,respectively,the significance is about 3.9?.There may be a resonant state around 4.47 GeV in the line shape of cross section e+e-???(2S).We need more data to reduce the statistical error of cross section measurement and confirm the existence of these resonant structures. |
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