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 T₄ₐ (Q=c or b) at lowest order in ₒ 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 T₄₂ hadronic decay and electromagnetic decay, respectively. Combining our results with the T₄₂ 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 10^3--10^4 for T₄₂, and 10^5--10^6 for T₄₂, at the LHC. The detecting prospect is promising. In addition, the decay widths of T₄₁ are estimated based on simple dimensional analysis as well as velocity scaling rule.