Can NRQCD explain the $\gamma\gamma^* \to \eta_c$ transition form factor data?
Abstract
Unlike the bewildering situation in the form factor, a widespread view is that perturbative QCD can decently account for the recent \textsc{BaBar} measurement of transition form factor. The next-to-next-to-leading order (NNLO) perturbative correction to the form factor, is investigated in the NRQCD factorization framework for the first time. As a byproduct, we obtain by far the most precise order- NRQCD matching coefficient for the process. After including the substantial negative order- correction, the good agreement between NRQCD prediction and the measured form factor is completely ruined over a wide range of momentum transfer squared. This eminent discrepancy casts some doubts on the applicability of NRQCD approach to hard exclusive reactions involving charmonium.
Keywords
Cite
@article{arxiv.1505.02665,
title = {Can NRQCD explain the $\gamma\gamma^* \to \eta_c$ transition form factor data?},
author = {Feng Feng and Yu Jia and Wen-Long Sang},
journal= {arXiv preprint arXiv:1505.02665},
year = {2015}
}
Comments
6 pages, 3 figures and 1 table; adding Eqs.(8) and (9) as well as some references, correcting errors in Table 1, updating Fig.3 to include the "light-by-light" contributions, devoting a paragraph to discuss why our strategy of interpreting the NNLO corrections is justified; Accepted by PRL