A Study of J/psi-->gamma gamma V(rho,phi) Decays with the BESII Detector

TL;DR

This study analyzes radiative J/psi decays into gamma gamma V (V=rho or phi) using BESII data, discovering a resonance X(1424) with specific mass, width, and branching ratios, and setting upper limits for certain decay modes.

Contribution

First observation and measurement of the X(1424) resonance in J/psi radiative decays with detailed mass, width, and branching ratio determinations.

Findings

Resonance X(1424) observed at 1424 MeV/c^2

Measured width of X(1424) is approximately 101 MeV/c^2

Branching ratio for J/psi to gamma X(1424) to gamma gamma rho is about 1.07e-4

Abstract

Using a sample of $58\times 10^6$ $J/\psi$ events collected with the BESII detector, radiative decays $J/\psi\to\gamma\gamma V$, where $V=\rho$ or $\phi$, are studied. A resonance around 1420 MeV/c$^2$ (X(1424)) is observed in the $\gamma\rho$ mass spectrum. Its mass and width are measured to be $1424\pm 10(stat)\pm 11(sys)$ MeV/c$^2$ and $ 101.0\pm 8.8 \pm 8.8$ MeV/c$^2$, respectively, and its branching ratio $B(J/\psi\to \gamma X(1424)\to \gamma \gamma \rho)$ is determined to be $(1.07\pm0.17 \pm 0.11)\times 10^{-4}$. A search for $X(1424)\to \gamma\phi$ yields a 95% C.L. upper limit $B(J/\psi\to \gamma X(1424)\to \gamma\gamma \phi) < 0.82 \times 10^{-4}$.