Photoproduction of heavy quarkonium at the ILC

We study the photoproduction of the heavy quarkonium at the future International Linear Collider (ILC) within the nonrelativistic QCD theory. We focus on the production channel via the subprocess gamma gamma -> vertical bar[Q (Q) over bar'](1) (n)> + Q' + Q, where Q and Q' stand for the heavy c or b quark, respectively vertical bar[Q (Q) over bar'](1) (n)> stands for the color-singlet S-wave quarkonium, i. e., eta(c) (vertical bar[c (c) over bar](1) (S-1(0))>), J/psi(vertical bar[c (c) over bar](1) (S-3(1))>), B-c (vertical bar[c (b) over bar](1) (S-1(0))>), B*(c) (vertical bar[c (b) over bar](1) (S-1(0))>), eta(b) (vertical bar[b (b) over bar](1) (S-1(0))>) and Upsilon(vertical bar[b (b) over bar](1) (S-3(1))>) , respectively. To improve the calculation efficiency, we adopt the improved helicity amplitude approach to deal with the difficulty of calculating the expressions for the yields when the quark masses cannot be neglected. Total and differential photoproduction cross sections, together with their uncertainties, have been presented. It is noted that a sizable number of vertical bar cc >-charmonium and vertical bar cb > bi-quarkonium events can be generated at the ILC. More specifically, we predict (2.4(-0.6)(+0.8)) x 10(6) eta(c) , (4.7(-1.1)(+1.6)) x 10(6) J/psi , (8.6(-1.9)(+2.3)) x 10(3) B-c , (4.6(-0.9)(+1.3)) x 10(4) and (6.6 +/- 1.2) x 10(3) eta(b) events to be generated in one operation year at the ILC under the condition of ffiffiffi root S = 500 GeV and 1036 cm(-2)s(-1).