Feasibility Study of $e^{+}{e}^{-}\to {\eta }_{c}J/\psi$ Production and Fully-Charmed Tetraquark Searches at STCF

Abstract

The proposed high-luminosity Super Tau-Charm Facility (STCF) offers a clean experimental environment for threshold studies of exotic hadrons. In this Letter, we evaluate the expected significance for the fully-charmed vector tetraquark candidate $T_{4c}$ in the $e^{+}{e}^{-}\to {\eta }_{c}J/\psi$ channel at the STCF. Using Monte Carlo simulations of an energy scan from $\sqrt{s}=6.71$ to $6.79\mathrm{GeV}$ with $100{\mathrm{fb}}^{-1}$ per point, we adopt a high-efficiency single-tag (ST) reconstruction of $J/\psi$ leptonic decays as the primary strategy, with a double-tag (DT) reconstruction of ${\eta }_c\to K^{+}{K}^{-}{\pi }^0$ retained as an independent cross-check. Because the signal cross section is governed by the still-uncertain dielectron width ${\Gamma }_{ee}$, we consider three benchmark hypotheses, ${\Gamma }_{ee}=0.25,0.5,1\mathrm{eV}$. The corresponding expected ST significances are $5.1\sigma$, $10.6\sigma$, and $20.5\sigma$, respectively. These results indicate that the STCF can provide meaningful sensitivity to fully-charmed tetraquark states near threshold.