1. chinaXiv:201609.01035 [pdf]

Next-to-next-to-leading-order QCD corrections to $\chi_c0,2\rightarrow \gamma\gamma$

Wen-Long Sang; Feng Feng; Yu Jia; Shuang-Ran Liang
Subjects: Physics >> Nuclear Physics

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 (NRQCD) factorization. The order-α2s?short-distance coefficients associated with each helicity amplitude are presented in a semi-analytic form, including the "light-by-light" contributions. With substantial NNLO corrections, we find disquieting discrepancy when confronting our state-of-the-art predictions with the latest \textsf{BESIII} measurements, especially fail to account for the measured?χc2→γγwidth. Incorporating the effects of spin-dependent forces would even exacerbate the situation, since it lifts the degeneracy between the nonperturbative NRQCD matrix elements of?χc0?and?χc2?toward the wrong direction. We also present the order-α2s?predictions to?χb0,2→γγ, which await the future experimental test.

submitted time 2016-09-14 Hits1827， Downloads1026， Comment 0