Artigo Acesso aberto Revisado por pares

Next-to-next-to-leading-order radiative corrections to e+e− → χcJ + γ at B factory

2020; Springer Nature; Volume: 2020; Issue: 10 Linguagem: Inglês

10.1007/jhep10(2020)098

ISSN

1127-2236

Autores

Wen-Long Sang, Feng Feng, Yu Jia,

Tópico(s)

High-Energy Particle Collisions Research

Resumo

A bstract Within the nonrelativistic QCD (NRQCD) factorization framework, we have computed the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the exclusive production of P -wave spin-triplet charmonia χ cJ ( J = 0 , 1 , 2) accompanied with a hard photon at B factory. For the first time, we have explicitly verified the validity of NRQCD factorization for exclusive P -wave quarkonium production to two-loop order. Unlike the χ cJ electromagnetic decays, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections are found to be smaller than the $$ \mathcal{O} $$ O ( α s ) corrections in all three channels e + e − → χ c 0 , 1 , 2 + γ . In particular, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections appear moderate for χ c 1 + γ case, and marginal for χ c 0 + γ . Moreover, the predictions in next-to-next-to-leading order (NNLO) accuracy for the production rates of χ c 0 , 1 + γ are insensitive to the renormalization and factorization scales. All these features may indicate that perturbative expansion in these two channels exhibits a decent convergence behavior. By contrast, both the $$ \mathcal{O} $$ O ( α s ) and $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the χ c 2 + γ production rate are sizable, which reduce the Born order cross section by one order of magnitude after including the NNLO perturbative corrections. Taking the values of the long-distance NRQCD matrix elements from nonrelativistic potential model, our prediction to χ c 1 + γ production rate is consistent with the recent Belle measurement. The NNLO predictions to the χ c 0 , 2 + γ production rates are much smaller than that for χ c 1 + γ , which seems to naturally explain why the e + e − → χ c 0 , 2 + γ channels have escaped experimental detection to date.

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