Two-loop form factors for pseudo-scalar quarkonium production and decay

We present the analytic expressions for two-loop form factors production or decay of pseudo-scalar quarkonia, in a scheme where quarks are produced at threshold. consider amplitude process $\gamma \gamma \leftrightarrow {^1S_0^{[1]}}$, that was previously known only numerically, as well processes $gg g {^1S_0^{[8]}}$ and {^1S_0^{[8]}}$, which have not been computed before. The corrections to {^1S_0^{[1]}}$ last missing ingredients full NNLO calculation $\eta_Q$ hadro-production. discuss how singularity structure amplitudes is affected by threshold kinematics, particular introduces Coulomb singularities. In this context, we first show usual infrared singularities degenerates then extract anomalous dimensions governing colour-singlet octet channels, latter being presented here time. give high-precision numerical results hard functions, can be used phenomenological studies NNLO.