Double distributions and evolution equations
- Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)
Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements {l_angle}p{sup {prime}}{vert_bar}O(0,z){vert_bar}p{r_angle} of quark and gluon light-cone operators. In our previous papers we used two types of nonperturbative functions parametrizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions F{sub {zeta}}(X;t). Here we discuss in more detail the double distributions (DD{close_quote}s) and evolution equations which they satisfy. We propose simple models for F(x,y;t=0) DD{close_quote}s with correct spectral and symmetry properties which also satisfy the reduction relations connecting them to the usual parton densities f(x). In this way, we obtain self-consistent models for the {zeta} dependence of nonforward distributions. We show that, for small {zeta}, one can easily obtain nonforward distributions (in the X{gt}{zeta} region) from the parton densities: F{sub {zeta}}(X;t=0){approx}f(X{minus}{zeta}/2). {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 289057
- Journal Information:
- Physical Review, D, Vol. 59, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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