Resonance-like structure of triangle singularity

Abstract

An enhancement in the invariant mass spectrum of certain hadronic reactions is often associated with the presence of a new, unstable state. However, there are cases where a signal can be explained purely in terms of kinematics, without the need for a new state. In this paper, we examine a general hadronic reaction in which the intermediate on-shell particles form a triangle loop. By utilizing some potential triangle singularity candidates, we demonstrate the occurrence of an enhancement in the invariant mass spectrum of the final hadronic state. To illustrate the resonance-like structure of the triangle singularity, we employ a Breit-Wigner amplitude with a polynomial background. We argue that, with the presence of error bars, the Breit-Wigner model can be indistinguishable from the enhancements caused by triangle loops. As a future prospect, we propose the development of a deep neural network capable of differentiating true resonance enhancements from those arising from triangle loops.