Proposal to detect a moving triangle singularity in $ψ(2S) \to π^+ π^- K^+ K^-$ process

Abstract

In this work, we propose that there exists a moving triangle singularity in the $ψ(2S) \to π^+ π^- K^+ K^-$ process, whose position can vary from 1.158 to 1.181 GeV in the invariant mass spectrum of $K^+K^-$. After a precise analysis on this process, it turns out that after doing some cuts on $m_{π^+π^-}$, experiments do have the opportunity to observe this triangle singularity. In addition, when changing the cuts on $m_{π^+π^-}$, the movement of the predicted triangle singularity can also be observed. Thus, we suggest future experiments, especially Super Tau-Charm Facility (STCF), to do an anlysis on the $ψ(2S) \to π^+ π^- K^+ K^-$ process to verify our prediction.