O(αs2) corrections to J/ψ + χc0,1,2 production at B factories

Abstract

We compute the O(αs2) corrections to the exclusive channels e+e−→J/ψ+χcJ (J=0,1,2) at s=10.58 GeV within the nonrelativistic QCD (NRQCD) factorization framework. The validity of NRQCD factorization at O(αs2) has been confirmed for these double-charmonium exclusive production processes. We analyze the impact of the O(αs2) corrections on the polarized and unpolarized cross sections, as well as the J/ψ angular distributions, which largely reduce the renormalization scale dependence but increase the O(αs) NRQCD predictions to some extent for χc0,1. With high numerical accuracy, our predictions for σ(J/ψ+χc1,2) through O(αs2) are compatible with the upper limit of the Belle measurement. Although the theoretical prediction for σ(J/ψ+χc0) is consistent with both Belle and BaBar measurements within uncertainties, there still exists serious tension between the predicted and the measured profiles for the J/ψ angular distribution. Regarding the bright observation prospect of the e+e−→J/ψ+χc1,2 channels in Belle 2 experiment, it is interesting to compare the future measurements with our NRQCD predictions. The more accurate measurement of e+e−→J/ψ+χ0 at Belle 2 will also help to clarify the long-standing puzzle of J/ψ angular distribution.