Leptoproduction of J/psi

Abstract

We study leptoproduction of $J/ψ$ at large $Q^2$ within the nonrelativistic QCD (NRQCD) factorization formalism. The cross section is dominated by color-octet terms that are of order $α_s$. The color-singlet term, which is of order $α^2_s$, is shown to be a small contribution to the total cross section. We also calculate the tree diagrams for color-octet production at order $α^2_s$ in a region of phase space where there is no leading color-octet contribution. We find that in this regime the color-singlet contribution dominates. We argue that non-perturbative corrections arising from diffractive leptoproduction, higher twist effects, and higher order terms in the NRQCD velocity expansion should be suppressed as $Q^2$ is increased. Therefore, the color-octet matrix elements $< {\cal O}_8^ψ(^1S_0)>$ and $<{\cal O}_8^ψ(^3P_0)>$ can be reliably extracted from this process. Finally, we point out that an experimental measurement of the polarization of leptoproduced $J/ψ$ will provide an excellent test of the NRQCD factorization formalism.