Abstract:
I review the status of the extraction of NRQCD color-octet
$J/\psi$ production matrix elements. Large theoretical
uncertainties in current extractions from hadroproduction
and photoproduction are emphasized. Leptoproduction of
$J/\psi$ is calculated within the NRQCD factorization
formalism. Color-octet contributions dominate the cross
section, allowing for a reliable extraction of $<{\cal
O}_8^{J/\psi}(^1S_0)>$ and $<{\cal O}_8^{J/\psi}(^3P_0)>$. A
comparison with preliminary data from the H1 collaboration
shows that leading order color-octet mechanisms agree with
the measured total cross section for $Q^2 > 4m_c^2$, while
the color-singlet model underpredicts the cross section by a
factor of 5.