Exclusive $eta_b$ decay to double $J/\psi$ at next-to-leading order in $alpha_s$

Abstract

Within the nonrelativistic QCD (NRQCD) factorization framework, we calculate the exclusive decay process \eta_b \to J/\psi J/\psi to next-to-leading order in the strong coupling constant, while at leading order in charm quark relative velocity. It is found that this new contribution to the amplitude is comparable in magnitude with the previously calculated relativistic correction piece, but differs by a phase about 90^\circ. Including this new contribution will increase the previous prediction to B(\eta_b \to J/\psi J/\psi) substantially, thus brightening the discovery potential of this clean hadronic decay channel of \eta_b in the forthcoming LHC experiment.