Observation of a State X(2600) in the π+ π-η' System in the Process J/ψ → γπ+π-η'

Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I; Ban, Y.; Batozskaya, V; Becker, D.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bloms, J.; Bortone, A.; Boyko, I; Briere, R. A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Chelkov, G.; Chen, C.; Chen, G.; Chen, H. S.; Chen, M. L.

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摘要

Based on (10087 +/- 44) x 10(6) J/psi events collected with the BESIII detector, the process J/psi -> gamma pi(+)pi(-) eta'is studied using two largest decay channels of the eta' meson,eta' -> gamma pi(+)pi(-)and eta' -> eta pi(+)pi(-), eta ->gamma gamma.A new resonance, which we denote as the X(2600), is observed with a statistical significance larger than 20 sigma in the pi(|) pi(-) eta' invariant mass spectrum, and it has a connection to a structure around 1.5 GeV/c(2) in the pi(|) pi(-) invariant mass spectrum. A simultaneous fit on the pi(|) pi(-) eta' invariant mass spectra with the two eta' decay modes indicates that the mass and width of the X(2600) state are 2618.3 +/- 2.0(-1.4)+(16.3) MeV/c(2) and 195 +/- 5(-17)(+26) MeV, where the first uncertainties are statistical, and the second systematic.

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MONTE-CARLO DECAY