Study of two-photon decays of pseudoscalar mesons via $J/\ddot{I}ˆ$ radiative decays

Abstract

Using a sample of $4.48\times 10^8$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons $\ddot{I}{€}^0$, $\hat{I}\cdot$, $\hat{I}{\cdot }^{\prime }$, $\hat{I}\cdot (1405)$, $\hat{I}\cdot (1475)$, $\hat{I}\cdot (1760)$, and $X(1835)$ in $J/\ddot{I}ˆ$ radiative decays using $\ddot{I}ˆ(3686)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}J/\ddot{I}ˆ$ events. The $\ddot{I}{€}^0$, $\hat{I}\cdot$ and $\hat{I}{\cdot }^{\prime }$ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be $B(J/\ddot{I}ˆ\to {\hat{I}}^3\ddot{I}{€}^0\to 3{\hat{I}}^3)=(3.57\pm 0.12\pm 0.16)\times 10^{-5}$, $B(J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}\cdot \to 3{\hat{I}}^3)=(4.42\pm 0.04\pm 0.18)\times 10^{-4}$, and $B(J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }^{\prime }\to 3{\hat{I}}^3)=(1.26\pm 0.02\pm 0.05)\times 10^{-4}$, where the first errors are statistical and the second systematic. No clear signal for $\hat{I}\cdot (1405)$, $\hat{I}\cdot (1475)$, $\hat{I}\cdot (1760)$ or $X(1835)$ is observed in the two-photon mass spectra, and upper limits at the $90\%$ confidence level on the product branching fractions are obtained.