Scaling Limit of Deeply Virtual Compton Scattering

Abstract

I outline a perturbative QCD approach to the analysis of the deeply virtual Compton scattering process ${\gamma }^{\ast }p\to \gamma p^{\prime }$ in the limit of vanishing momentum transfer $t=(p^{\prime }-p{)}^2$. The DVCS amplitude in this limit exhibits a scaling behaviour described by a two-argument distributions $F(x,y)$ which specify the fractions of the initial momentum $p$ and the momentum transfer $r\equiv p^{\prime }-p$ carried by the constituents of the nucleon.The kernel $R(x,y;\xi ,\eta )$ governing the evolution of the non-forward distributions $F(x,y)$ has a remarkable property: it produces the GLAPD evolution kernel $P(x/\xi )$ when integrated over $y$ and reduces to the Brodsky-Lepage evolution kernel $V(y,\eta )$ after the $x$-integration. This property is used to construct the solution of the one-loop evolution equation for the flavour non-singlet part of the non-forward quark distribution.

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