16 research outputs found
Gauge Invariance and Anomalous Dimensions of a Light-Cone Wilson Loop in Light-Like Axial Gauge
Complete two-loop calculation of a dimensionally regularized Wilson loop with
light-like segments is performed in the light-like axial gauge with the
Mandelstam-Leibbrandt prescription for the gluon propagator. We find an
expression which {\it exactly} coincides with the one previously obtained for
the same Wilson loop in covariant Feynman gauge. The renormalization of Wilson
loop is performed in the \MS-scheme using a general procedure tailored to the
light-like axial gauge. We find that the renormalized Wilson loop obeys a
renormalization group equation with the same anomalous dimensions as in
covariant gauges. Physical implications of our result for investigation of
infrared asymptotics of perturbative QCD are pointed out.Comment: 24 pages and 4 figures (included), LaTeX style, UFPD-93/TH/23,
UPRF-93-366, UTF-93-29
Light--like Wilson loops and gauge invariance of Yang--Mills theory in 1+1 dimensions
A light-like Wilson loop is computed in perturbation theory up to for pure Yang--Mills theory in 1+1 dimensions, using Feynman and
light--cone gauges to check its gauge invariance. After dimensional
regularization in intermediate steps, a finite gauge invariant result is
obtained, which however does not exhibit abelian exponentiation. Our result is
at variance with the common belief that pure Yang--Mills theory is free in 1+1
dimensions, apart perhaps from topological effects.Comment: 10 pages, plain TeX, DFPD 94/TH/
Dijet Rapidity Gaps in Photoproduction from Perturbative QCD
By defining dijet rapidity gap events according to interjet energy flow, we
treat the photoproduction cross section of two high transverse momentum jets
with a large intermediate rapidity region as a factorizable quantity in
perturbative QCD. We show that logarithms of soft gluon energy in the interjet
region can be resummed to all orders in perturbation theory. The resummed cross
section depends on the eigenvalues of a set of soft anomalous dimension
matrices, specific to each underlying partonic process, and on the
decomposition of the scattering according to the possible patterns of hard
color flow. We present a detailed discussion of both. Finally, we evaluate
numerically the gap cross section and gap fraction and compare the results with
ZEUS data. In the limit of low gap energy, good agreement with experiment is
obtained.Comment: 37 pages, Latex, 17 figure
The B-Meson Distribution Amplitude in QCD
The B-meson distribution amplitude is calculated using QCD sum rules. In
particular we obtain an estimate for the integral relevant to exclusive
B-decays \lambda_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated
parametrization of the distribution amplitude is suggested.Comment: 17 pages, 8 figures, Latex styl
Review of AdS/CFT Integrability, Chapter V.2: Dual Superconformal Symmetry
Scattering amplitudes in planar N=4 super Yang-Mills theory reveal a
remarkable symmetry structure. In addition to the superconformal symmetry of
the Lagrangian of the theory, the planar amplitudes exhibit a dual
superconformal symmetry. The presence of this additional symmetry imposes
strong restrictions on the amplitudes and is connected to a duality relating
scattering amplitudes to Wilson loops defined on polygonal light-like contours.
The combination of the superconformal and dual superconformal symmetries gives
rise to a Yangian, an algebraic structure which is known to be related to the
appearance of integrability in other regimes of the theory. We discuss two dual
formulations of the symmetry and address the classification of its invariants.Comment: 22 pages, see also overview article arXiv:1012.3982, v2: references
to other chapters updated, v3 added references, typos fixe
Discontinuous Behaviour of perturbative Yang Mills theories in the limit of dimensions
We calculate in dimensions and in light-cone gauge (LCG) the
perturbative contribution to a rectangular Wilson loop in the
(t,x)-plane coming from diagrams with a self-energy correction in the vector
propagator. In the limit the result is finite, in spite of the
vanishing of the triple vector vertex in LCG, and provides the expected
agreement with the analogous calculation in Feynman gauge.Comment: DFPD 99/TH/13, RevTex, 15 pages, no figure