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

分类： 物理学 >> 核物理学 提交时间： 2016-09-14

Wen-Long Sang Feng Feng Yu Jia Shuang-Ran Liang

摘要： 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.

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