1,795 research outputs found
Deep inelastic scattering as x -> 1 using soft-collinear effective theory
Soft-collinear effective theory (SCET) is used to sum Sudakov
double-logarithms in the x ->1 endpoint region for the deep inelastic
scattering structure function. The calculations are done in both the target
rest frame and the Breit frame. The separation of scales in the effective
theory implies that the anomalous dimension of the SCET current is linear in ln
mu, and the anomalous dimension for the Nth moment of the structure function is
linear in ln N, to all orders in perturbation theory. The SCET formulation is
shown to be free of Landau pole singularities. Some important differences
between the deep inelastic structure function and the shape function in B decay
are discussed.Comment: 19 pages, minor typos fixed, and a comment added on the longitudinal
structure functio
Chiral Perturbation Theory
The basic ideas and power counting rules of chiral perturbation theory are
discussed. The formalism of velocity dependent fields for baryons, and for
hadrons containing a heavy quark, is explained. (Invited Talk, 1993 QCD
Rencontres de Moriond)Comment: (uses harvmac, 9 pages, 1 figure), UCSD/PTH 93-1
Infrared Scales and Factorization in QCD
Effective field theory methods are used to study factorization of the deep
inelastic scattering cross-section. The cross-section is shown to factor in
QCD, even though it does not factor in perturbation theory for some choices of
the infrared regulator. Messenger modes are not required in soft-collinear
effective theory for deep inelastic scattering as x -> 1.Comment: 5 pages, 2 figures, revtex
Moments of generalized parton distribution functions and the nucleon spin contents
It is shown that, based only on two empirically known facts besides two
reasonable theoretical postulates, we are inevitably led to a conclusion that
the quark orbital angular momentum carries nearly half of the total nucleon
spin. We also perform a model analysis to find that the quark spin fraction
is extremely sensitive to the pion mass, which may resolve the
discrepancy between the observation and the prediction of the recent lattice
QCD simulation carried out in the heavy pion region.Comment: LaTeX, 8 pages, 1 figur
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