6533b82bfe1ef96bd128d5f4

RESEARCH PRODUCT

η(′)→π+π−γ(*) in large- Nc chiral perturbation theory

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We present a calculation of the decays ${\ensuremath{\eta}}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\gamma}}^{(*)}$ at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-${N}_{c}$ chiral perturbation theory. The numerical evaluation of the results is performed successively at LO, NLO, and NNLO, fitting the relevant low-energy constants to the available experimental data. We discuss the widths and decay spectra of ${\ensuremath{\eta}}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$ as well as ${\ensuremath{\eta}}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{l}^{+}{l}^{\ensuremath{-}}$, with $l=e$, $\ensuremath{\mu}$.