Feng, F (reprint author), China Univ Min & Technol, Beijing 100083, Peoples R China.
Unlike the bewildering situation in the gamma gamma* -> pi form factor, a widespread view is that perturbative QCDcan decently account for the recentBABAR measurement of the gamma gamma* ->eta(c) transition formfactor. The nextto- next-to-leading-order perturbative correction to the gamma gamma* ->eta(c,b) form factor, is investigated in the nonrelativistic QCD (NRQCD) factorization framework for the first time. As a byproduct, we obtain, by far, the most precise order-alpha(2)(s) NRQCD matching coefficient for the eta(c,b) -> gamma gamma process. After including the substantial negative order-alpha(2)(s) correction, the good agreement between NRQCD prediction and the measured gamma gamma* ->eta(c) form factor is completely ruined over a wide range of momentum transfer squared. This eminent discrepancy casts some doubts on the applicability of the NRQCD approach to hard exclusive reactions involving charmonium.
National Natural Science Foundation of China [11505285, 11447031]
; Fundamental Research Funds for the Central Universities [SWU114003, XDJK2016C067]
; National Natural Science Foundation of China (DGF and NSFC) [11475188, 11261130311, CRC110]
; IHEP Innovation Grant [Y4545170Y2]
; State Key Lab for Electronics and Particle Detectors
; Open Project Program of State Key Laboratory of Theoretical Physics [Y4KF081CJ1]