Scale dependence of the chiral-odd twist-3 distributions $h_L(x)$ and $e(x)$

Abstract

We evaluate the complete leading-order evolution kernels for the chiral-odd twist-3 distributions $e(x)$ and ${\tilde{h}}_L(x)$ of the nucleon. We establish the connection between the evolution equations in light-cone position and light-cone fraction representations, which makes a correspondence between the non-local string operator product expansion and the QCD-inspired parton model. The compact expression obtained for the local anomalous dimension matrix coincides with previous calculations. In the multicolour QCD as well as in the large-$x$ limit the twist-3 distributions obey simple DGLAP equations. Combining these two limits, we propose improved DGLAP equations and compare them numerically with the solutions of the exact evolution equations.

Comments: 30 pages, LaTeX, 5 eps figures; typos fixed, preprint number added