Electromagnetic and hadronic decay of fully heavy tetraquarks

In this study, we compute the electromagnetic and hadronic decay widths of the S-wave fully heavy tetraquark T4Q ($Q=c$ or b) at lowest order in αₛ and v, in the framework of nonrelativistic QCD. The short-distance coefficients are determined through the standard procedure of matching. The nonperturbative long-distance matrix elements are related to the phenomenological four-body Schr\"odinger wave functions at the origin, whose values are taken from literature. The branching fractions are predicted to be around 10^-3 and 10^-6 for the T4c hadronic decay and electromagnetic decay, respectively. Combining our results with the T4c production cross sections at the LHC, we also predict the event numbers for various decay channels. With integrated luminosity L=100 fb^-1, it is expected that the event numbers can reach 10³--10⁴ for T4c→γγ, and 10⁵--10⁶ for T4c→LH, at the LHC. The detecting prospect is promising. In addition, the decay widths of T4b are estimated based on simple dimensional analysis as well as velocity scaling rule.