Baxter equation beyond wrapping

The Baxter-like functional equation encoding the spectrum of anomalous dimensions of Wilson operators in maximally supersymmetric Yang-Mills theory available to date ceases to work just before the onset of wrapping corrections. In this paper, we work out an improved finite-difference equation by incorporating nonpolynomial effects in the transfer matrix entering as its ingredient. This yields a self-consistent asymptotic finite-difference equation valid at any order of perturbation theory. Its exact solutions for fixed spins and twists at and beyond wrapping order give results coinciding with the ones obtained from the asymptotic Bethe Ansatz. Correcting the asymptotic energy eigenvalues by the Luescher term, we compute anomalous dimensions for a number of short operators beyond wrapping order.Comment: 10 page

Scaling violations and off-forward parton distributions: leading order and beyond

We give an outline of a formalism for the solution of the evolution equations for off-forward parton distributions in leading and next-to-leading orders based on partial conformal wave expansion and orthogonal polynomials reconstruction.Comment: 3 pages, LaTeX, 3 figures, Talk given at the 7th International Workshop on Deep Inelastic Scattring and QCD, DESY-Zeuthen, April 19-23, 199

NLO evolution kernels for skewed transversity distributions

We present a calculation of the two-loop evolution kernels of the twist-two transversally polarized quark and linearly polarized gluon skewed parton distributions in the minimal subtraction scheme and discuss a solution of the evolution equations suitable for numerical implementations.Comment: 14 pages LaTe

Long-range SL(2) Baxter equation in N=4 super-Yang-Mills theory

Relying on a few lowest order perturbative calculations of anomalous dimensions of gauge invariant operators built from holomorphic scalar fields and an arbitrary number of covariant derivatives in maximally supersymmetric gauge theory, we propose an all-loop generalization of the Baxter equation which determines their spectrum. The equation does not take into account wrapping effects and is thus asymptotic in character. We develop an asymptotic expansion of the deformed Baxter equation for large values of the conformal spin and derive an integral equation for the cusp anomalous dimension.Comment: Latex, 11 page

Exclusive electroproduction of lepton pairs as a probe of nucleon structure

We suggest the measurement of exclusive electroproduction of lepton pairs as a tool to study inter-parton correlations in the nucleon via generalized parton distributions in the kinematical region where this process is light-cone dominated. We demonstrate how the single beam-spin asymmetry allows to perform such kind of analysis and give a number of predictions for several experimental setups. We comment on other observables which allow for a clean separation of different species of generalized parton distributions.Comment: 4 pages RevTeX4, 6 figures, typo fixe

Theory of deeply virtual Compton scattering on the nucleon

We compute the cross section for leptoproduction of the real photon off the nucleon, which is sensitive to the deeply virtual Compton scattering amplitude with power accuracy. Our considerations go beyond the leading twist and involve the complete analysis in the twist-three approximation. We discuss consequences of the target and lepton beam polarizations for accessing the generalized parton distributions from experimental measurements of the azimuthal angular dependence of the final state photon or nucleon. We introduce several sets of asymmetries, defined as Fourier moments with respect to the azimuthal angle, which allow for a clear separation of the twist-two and -three sectors. Relying on a simple ansatz for the generalized parton distributions, we give quantitative estimates for azimuthal and spin asymmetries, discuss the uncertainties of these predictions brought in by radiative corrections, and compare them with experimental data as well as other theoretical expectations. Furthermore, we derive a general parametrization of the DVCS amplitudes in the region of small Bjorken variable.Comment: 76 pages, LaTeX, 16 figures, 3 tables, minor correction

Twist-three observables in deeply virtual Compton scattering on the nucleon

We study twist-three effects in deeply virtual Compton scattering on an unpolarized spin-1/2 target. A careful definition of observables as Fourier moments w.r.t. the azimuthal angle allows for a clear separation of twist-two and -three effects. Although the latter are power suppressed, they give leading contributions to the twist-three asymmetries and do not affect the twist-two observables.Comment: 10 pages, LaTe

\cN = 1 supersymmetric constraints for evolution kernels

We provide a complete set of supersymmetric constraints for the anomalous dimensions of the conformal twist-two operators to all orders of perturbation theory. Employing them we derive new relations between the exclusive evolution kernels and apply them in QCD in order to get definite predictions at leading order and beyond.Comment: LaTeX, npb.sty required, 4 pages, Talk given at the 7th International Workshop on Deep Inelastic Scattring and QCD, DESY-Zeuthen, April 19-23, 199

Reconstruction of non-forward evolution kernels

We develop a framework for the reconstruction of the non-forward kernels which govern the evolution of twist-two distribution amplitudes and off-forward parton distributions beyond leading order. It is based on the knowledge of the special conformal symmetry breaking part induced by the one-loop anomaly and conformal terms generated by forward next-to-leading order splitting functions, and thus avoids an explicit two-loop calculation. We demonstrate the formalism by applying it to the chiral odd and flavour singlet parity odd sectors.Comment: 13 pages, LaTeX, typos fixe

Integrability and WKB solution of twist-three evolution equations

We identify an integrable one-dimensional inhomogeneous three-site open spin chain which arises in the problem of diagonalization of twist-three quark-gluon evolution equations in QCD in the chiral-odd sector. Making use of the existence of a non-trivial `hidden' integral of motion the problem of diagonalization of the evolution kernels is reduced to the study of a second order finite-difference equation which is solved in WKB approximation for large conformal spins of the three-particle system. The energies (alias anomalous dimensions) of eigenstates with different scale dependence are found in limiting cases and compared with numerical calculations.Comment: 26 pages, LaTeX, 4 figures; typos fixe