Diffractive JΨ leptoproduction as a way to measure the polarized gluon distribution

The cross section of diffractive JΨ lepto- (and photo-) production on a polarized target is calculated in the leading log approximation of pQCD assuming a nonrelativistic JΨ wave function. In this approximation the spin-spin asymmetry in the small x region is close to 2ΔGG for the γ∗ + p → JΨ + p reaction, providing a promising tool to study the spin dependent gluon distribution ΔG(x, q2).