Phys. Rev. Lett. 129, 042001 (2022) - Observation of a State $X(2600)$ in the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}\ensuremath{'}$ System in the Process $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}\ensuremath{'}$

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Observation of a State $X (2600)$ in the $π^{+} π^{-} η'$ System in the Process $J / ψ \to γ π^{+} π^{-} η'$

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. Lett. 129, 042001 – Published 19 July 2022

Abstract

Based on $(10087 \pm 44) \times 10^{6} J / ψ$ events collected with the BESIII detector, the process $J / ψ \to γ π^{+} π^{-} η^{'}$ is studied using two largest decay channels of the $η^{'}$ meson, $η^{'} \to γ π^{+} π^{-}$ and $η^{'} \to η π^{+} π^{-}$ , $η \to γ γ$ . A new resonance, which we denote as the $X (2600)$ , is observed with a statistical significance larger than $20 σ$ in the $π^{+} π^{-} η^{'}$ invariant mass spectrum, and it has a connection to a structure around ${1.5 GeV / c}^{2}$ in the $π^{+} π^{-}$ invariant mass spectrum. A simultaneous fit on the $π^{+} π^{-} η^{'}$ and $π^{+} π^{-}$ invariant mass spectra with the two $η^{'}$ decay modes indicates that the mass and width of the $X (2600)$ state are $2618.3 \pm 2. 0_{- 1.4}^{+ 16.3} MeV / c^{2}$ and $195 \pm 5_{- 17}^{+ 26} MeV$ , where the first uncertainties are statistical, and the second systematic.

Received 27 January 2022
Accepted 24 June 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.042001

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Published by the American Physical Society