Next-to-next-to-leading-order QCD corrections to ${\chi }_{c0,2}\to \gamma \gamma$

Wen-Long Sang, Feng Feng, Yu Jia +1

We calculate the next-to-next-to-leading-order (NNLO) perturbative corrections to $P$-wave quarkonia annihilation decay to two photons, in the framework of nonrelativistic QCD (NRQ…