Effect of off-diagonal parton distributions in diffractive vector meson electroproduction

We present a simple physical description of the off-diagonal gluon distribution ${g(x,x}^{\prime }{,Q}^2)$ and splitting function $P_{\mathrm{gg}}{(x,x}^{\prime })$ which enter the amplitude for diffractive vector meson production. We study the off-diagonal effects both on the evolution in $Q^2$ and on the input distribution. We predict the ratio $R$ of the off-diagonal to the diagonal gluon density, $x^{\prime }{g(x,x}^{\prime }{,Q}^2{)/xg(x,Q}^2)$, as a function of the kinematic variables. DOI: http://dx.doi.org/10.1103/PhysRevD.57.6692 © 1998 The American Physical Society