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

Abstracts

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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Keywords: QCD ;
Recommended references: Wen-Long Sang,Feng Feng,Yu Jia,Shuang-Ran Liang.(2016).Next-to-next-to-leading-order QCD corrections to $\chi_c0,2\rightarrow \gamma\gamma$.[ChinaXiv:201609.01035] (Click&Copy)
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[V1] 2016-09-14 08:28:15 chinaXiv:201609.01035V1 Download
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