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

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.