Resummation of Relativistic Corrections to e+ e- -> J/psi+eta_c

TL;DR

This paper refines the calculation of relativistic corrections to the e+ e- -> J/psi+eta_c process within NRQCD, resolving previous discrepancies between theory and experiment by incorporating several advanced effects and uncertainties.

Contribution

It introduces a comprehensive calculation including resummation, improved matrix elements, and interference effects, significantly enhancing the accuracy of theoretical predictions for double-charmonium production.

Findings

Theoretical predictions now align with experimental measurements.

Relativistic corrections and interference effects are crucial for accurate cross section estimates.

Uncertainty estimates improve confidence in the theoretical results.

Abstract

We present a new calculation, in the nonrelativistic QCD (NRQCD) factorization formalism, of the relativistic corrections to the double-charmonium cross section sigma[e+ e- -> J/psi+eta_c] at the energy of the Belle and BABAR experiments. In comparison with previous work, our calculation contains several refinements. These include the use of the improved results for the nonperturbative NRQCD matrix elements, the resummation of a class of relativistic corrections, the use of the vector-meson-dominance method to calculate the fragmentation contribution to the pure QED amplitude, the inclusion of the effects of the running of alpha, and the inclusion of the contribution that arises from the interference between the relativistic corrections and the corrections of next-to-leading order in alpha_s. We also present a detailed estimate of the theoretical uncertainty. We conclude that the discrepancy between the theoretical prediction for sigma[e+e- -> J/psi+eta_c] and the experimental measurements has been resolved.