Study on ${\eta }_{c2}({\eta }_{b2})$ electromagnetic decay into double photons

Li Yang, Wen-Long Sang, Hong-Fei Zhang +2

Within the framework of nonrelativistic QCD (NRQCD) factorization formalism, we compute the helicity amplitude as well as the decay width of ${\eta }_{Q2}$ ($Q=c,b$) electromagnetic deca…