Relativistic corrections to ${\rm Y}$ exclusive decay into double $S-$wave charmonia

Wen-Long Sang, Feng Feng, Yu-Qi Chen

Within the framework of nonrelativisitic QCD factorization formalism, we present the next-to-leading-order relativistic corrections to ${\rm Y}$ exclusive decay into ${\eta }_c$ plus $J/\psi$. Th…