Exploring Nucleon Structure through Sub- and Near-threshold $φ$-Meson Photoproduction

Abstract

We propose to investigate short-range correlations (SRCs) in nuclei by studying sub and near-threshold photoproduction of $φ$-meson. The feasibility of exploring this nuclear structure in electron-positron collision experiments such as Beijing Spectrometer III (BESIII) and Super $τ$-Charm Facility (STCF) was investigated by utilizing their beryllium-based ($^{9}$Be) beam pipe. The cross sections for these processes as well as the likelihood of detection by BESIII and STCF are calculated. Due to the limited number of events, BESIII is inadequate for the proposed measurement, while the future STCF provides a higher probability of successfully measuring this process. These findings suggest that electron-positron collider could play a valuable role in elucidating the fundamental physics behind the nuclear modification of parton distribution functions. This proposed analysis of photon-nucleon interactions represents uncharted territory, promising fresh prospects for applications in both particle and nuclear physics.

Figures (3)

• Figure 1: The near-threshold cross section of $\phi$-meson photoproduction as a function of incoming photon energy $E_\gamma$. Data from LEPS LEPS:2005hax and CLAS Dey:2014tfa are used in the fit. The solid-line (blue) is the energy fraction parameter model, with the fitted parameters $\sigma_0^{\gamma N} = 0.456 \pm 0.054 \,\rm{\mu b}$ and $\beta = 0.398 \pm 0.072$.
• Figure 2: Sub- and near-threshold $\phi$-meson photoproduction cross sections in $\gamma A$ collision, the interaction with free proton is also presented as comparison.
• Figure 6: (a): The photon enegy spectrums from the three-body decays $J/\psi \to \gamma \pi \pi$, as well as two-body decays $J/\psi \to \rho \pi$, $J/\psi (\psi(3686)) \to \gamma \eta (\eta')$. These processes offer photons ranging from below the threshold energy to above (the bold dashed line represents the threshold energy $E_\gamma \!=\! 1.57$ GeV). (b): The photon energy spectrums from combined $J/\psi$ and $\psi(3686)$ decay channels. These plots are obtained from the Monte Carlo truth information.