S. Gupta et P. Mathews, HIGHER ORDERS IN THE COLOR-OCTET MODEL OF J PSI PRODUCTION/, Physical review. D. Particles and fields, 56(5), 1997, pp. 3019-3029
We study the hadroproduction and photoproduction of (c) over bar c and
(b) over bar b mesons at low transverse momentum to high orders in th
e relative velocity of the pair, nu, in nonrelativistic QCD. We evalua
te cross sections to order nu(7) for eta(c), sufficient for studies of
photoproduction in the almost-elastic region. For all other charmoniu
m states we find the cross section to order nu(9), sufficient for stud
ies of the ratio of chi(c1) and chi(c2) production rates. We find recu
rrence formulas for generating terms at even higher orders, should the
y be needed.