Observation of pseudoscalar and tensor resonances in $J/\psi\rightarrow \gamma \phi \phi$

TL;DR

This study uses a large sample of $J/a9$ events to perform a partial wave analysis, confirming known resonances and discovering new pseudoscalar, scalar, and tensor states in the decay $J/a9 ightarrow \u03b3 \u03c6 \u03c6$, advancing understanding of meson spectroscopy.

Contribution

The paper reports the first observation of two new pseudoscalar states, $ ext{η}(2100)$ and $X(2500)$, in $J/a9$ decays, along with precise measurements of their resonance parameters.

Findings

Confirmed the existence of $ ext{η}(2225)$ with measured parameters.

Observed two new pseudoscalar states, $ ext{η}(2100)$ and $X(2500)$.

Detected scalar $f_0(2100)$ and tensor states $f_2(2010)$, $f_2(2300)$, $f_2(2340)$.

Abstract

Based on a sample of $(1310.6 \pm 10.5) \times 10^{6}$ $J/\psi$ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay $J/\psi\rightarrow \gamma \phi \phi$ is performed in order to study the intermediate states. Results of the partial wave analysis show that the structures are predominantly $0^{-+}$ states. The existence of the $\eta(2225)$ is confirmed, and its resonance parameters are measured. Two additional pseudoscalar states, the $\eta(2100)$ with a mass of $2050_{-24}^{+30}{}_{-26}^{+75}$~MeV/$c^{2}$ and a width of $250_{-30}^{+36}{}_{-164}^{+181}$~MeV/$c^{2}$ and the $X(2500)$ with a mass of $2470_{-19}^{+15}{}_{-23}^{+101}$~MeV/$c^{2}$ and a width of $230_{-35}^{+64}{}_{-33}^{+56}$~MeV/$c^{2}$, are observed. In addition to these three pseudoscalar states, the scalar state $f_0(2100)$, and three tensor states, the $f_2(2010)$, $f_2(2300)$ and $f_2(2340)$, are observed in the process $J/\psi\rightarrow \gamma \phi\phi$. The product branching fractions ${\cal B}$($J/\psi\rightarrow \gamma X)\times{\cal B}(X\rightarrow \phi \phi)$ are reported.