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

Renormalons in exclusive meson electroproduction

We discuss the possibility of measuring generalized parton distributions in exclusive electroproduction of mesons off the nucleon and estimate the uncertainty from perturbatively induced higher-twist corrections. We find that, while the magnitude of the cross section changes significantly taking into account twist-four contributions modeled via renormalons, the transverse spin asymmetry is weakly sensitive to them and displays the precocious scaling.Comment: 5 pages, Aipproc, 2 figure

Strong coupling expansion of Baxter equation in N=4 SYM

The anomalous dimensions of single-trace local Wilson operators with covariant derivatives in maximally supersymmetric gauge theory are believed to be generated from a deformed noncompact sl(2) Baxter equation. We perform a systematic expansion of this equation at strong coupling in the single-logarithmic limit of large conformal spin to overcome the limitation of the asymptotic nature of the equation. The analysis is reduced to Riemann-Hilbert problems for corresponding resolvents of Bethe roots in each order of the quasiclassical expansion. We explicitly construct the resolvents in the lowest two orders in strong coupling and find all local conserved charges of the underlying long-range spin chain.Comment: 12 page

Nonperturbative enhancement of superloop at strong coupling

We address the near-collinear expansion of NMHV six-particle scattering amplitudes at strong value of 't Hooft coupling in planar maximally supersymmetric Yang-Mills theory. We complement recent studies of this observable within the context of the Pentagon Operator Product Expansion, via the dual superWilson loop description, by studying effects of multiple scalar exchanges that accompany (or not) massive flux-tube excitations. Due to the fact that holes have a very small, nonperturbatively generated mass which is exponentially suppressed in 't Hooft coupling, their exchanges must be resummed in the ultraviolet limit. This procedure yields a contribution to the expectation value of the superloop which enters on equal footing with the classical area, --- a phenomenon which was earlier observed for MHV amplitudes. In all components, the near-massless scalar exchanges factorize from the ones of massive particles, at leading order in strong coupling.Comment: 22 pages, 2 figure