31 research outputs found
Comments on gluon scattering amplitudes via AdS/CFT
In this article we consider n gluon color ordered, planar amplitudes in N=4
super Yang Mills at strong 't Hooft coupling. These amplitudes are approximated
by classical surfaces in AdS_5 space. We compute the value of the amplitude for
a particular kinematic configuration for a large number of gluons and find that
the result disagrees with a recent guess for the exact value of the amplitude.
Our results are still compatible with a possible relation between amplitudes
and Wilson loops.
In addition, we also give a prescription for computing processes involving
local operators and asymptotic states with a fixed number of gluons. As a
byproduct, we also obtain a string theory prescription for computing the dual
of the ordinary Wilson loop, Tr P exp[ i\oint A ], with no couplings to the
scalars. We also evaluate the quark-antiquark potential at two loops.Comment: 27 pages, 9 figures,v3:minor correction
Role of N*(1650) in the near threshold pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions
We investigate the pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions at
beam energies near their thresholds within an effective Lagrangian model, where
the strangeness production proceeds via the excitation of N*(1650), N*(1710),
and N*(1720) baryonic resonances. It is found that the (1650) resonance
dominates both these reactions at near threshold energies. The contributions
from this resonance together with the final state interaction among the
outgoing particles are able to explain the observed beam energy dependence of
the ratio of the cross sections of the two reactions in the near threshold
region.Comment: Revised version, Fig. 4 is updated with the revised data, to appear
in Phys. Rev. C (Rapid Communications