Exclusive decays of fully heavy tetraquarks into light mesons

In this work, we investigate the exclusive decays of the fully-heavy tetraquark states T 4 c , b into light mesons, specifically π and K , using the framework of nonrelativistic quantum chromodynamics (NRQCD) and collinear QCD factorization for hard exclusive processes. We estimate the decay widths to be 10 − 9 GeV and 10 − 14 GeV for the decays T 4 c → π + π − and T 4 b → π + π − (and similarly for K + K − ), respectively. The branching ratio for T 4 c → π + π − ( K + K − ) is on the order of 10 − 8 , making it currently unobservable in existing experiments. The factorization of T 4 c , b into light hadrons shares similarities with the decay J / ψ → p p ¯ . However, unlike the latter process, the decay T 4 c , b → π + π − ( K + K − ) exhibits unique features that arise only in processes involving multiple incoming or outgoing particles. One such feature is the necessity of maintaining the i ϵ -prescription for the denominators or propagators due to the divergences in the kinematic region of interest. Employing the sector decomposition method, along with the aid of the Cheng-Wu theorem and the program, we present a systematic approach to handle the convolutions and phase-space integrations. This method can also be extended to similar processes, such as T 4 c , b → p p ¯ , as well as to phase-space integrations where each denominator is a linear combination of integration variables.