655 research outputs found
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
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