2,881 research outputs found
Next-to-Maximal Helicity Violating Amplitudes in Gauge Theory
Using the novel diagrammatic rules recently proposed by Cachazo, Svrcek, and
Witten, I give a compact, manifestly Lorentz-invariant form for tree-level
gauge-theory amplitudes with three opposite helicities.Comment: 12 pages, 1 figur
Twistor Space Structure of the Box Coefficients of N=1 One-loop Amplitudes
We examine the coefficients of the box functions in N=1 supersymmetric
one-loop amplitudes. We present the box coefficients for all six point N=1
amplitudes and certain all example coefficients. We find for ``next-to
MHV'' amplitudes that these box coefficients have coplanar support in twistor
space.Comment: 14 pages, minor typos correcte
Two-Loop -Diagrams from String Theory
Using the {\em cutting and sewing} procedure we show how to get Feynman
diagrams, up to two-loop order, of -theory with an internal SU(N)
symmetry group, starting from tachyon amplitudes of the open bosonic string
theory. In a properly defined field theory limit, we easily identify the
corners of the string moduli space reproducing the correctly normalized field
theory amplitudes expressed in the Schwinger parametrization.Comment: 28 pages, 12 figure
Relations between some analytic representations of one-loop scalar integrals
We compare several parametrized analytic expressions for an arbitrary
off-shell one-loop -point function in scalar field theory in -dimensional
space-time, and show their equivalence both directly and through path-integral
methods.Comment: 12 pages, NIKHEF-H/94-2
All Non-Maximally-Helicity-Violating One-Loop Seven-Gluon Amplitudes in N=4 Super-Yang-Mills Theory
We compute the non-MHV one-loop seven-gluon amplitudes in N=4
super-Yang-Mills theory, which contain three negative-helicity gluons and four
positive-helicity gluons. There are four independent color-ordered amplitudes,
(- - - + + + +), (- - + - + + +), (- - + + -+ +) and (- + - + - + +). The MHV
amplitudes containing two negative-helicity and five positive-helicity gluons
were computed previously, so all independent one-loop seven-gluon helicity
amplitudes are now known for this theory. We present partial information about
an infinite sequence of next-to-MHV one-loop helicity amplitudes, with three
negative-helicity and n-3 positive-helicity gluons, and the color ordering (- -
- + + ... + +); we give a new coefficient of one class of integral functions
entering this amplitude. We discuss the twistor-space properties of the
box-integral-function coefficients in the amplitudes, which are quite simple
and suggestive.Comment: 54 pages, v3 minor correction
On the Coupling of Gravitons to Matter
Using relationships between open and closed strings, we present a
construction of tree-level scattering amplitudes for gravitons minimally
coupled to matter in terms of gauge theory partial amplitudes. In particular,
we present examples of amplitudes with gravitons coupled to vectors or to a
single fermion pair. We also present two examples with massive graviton
exchange, as would arise in the presence of large compact dimensions. The gauge
charges are represented by flavors of dynamical scalars or fermions. This also
leads to an unconventional decomposition of color and kinematics in gauge
theories.Comment: RevTex, 4 page
A technique for loop calculations in non-Abelian gauge theories - with application to five gluon amplitude
A powerful tool for calculations in non-Abelian gauge theories is obtained by
combining the background field gauge, the helicity basis and the color
decomposition methods. It has reproduced the one-loop calculation of the
five-gluon amplitudes in QCD, is applicable to electroweak processes and
extendable to two-loop calculations.Comment: Latex 22 pages, 3 figure
The Last of the Finite Loop Amplitudes in QCD
We use on-shell recursion relations to determine the one-loop QCD scattering
amplitudes with a massless external quark pair and an arbitrary number (n-2) of
positive-helicity gluons. These amplitudes are the last of the unknown
infrared- and ultraviolet-finite loop amplitudes of QCD. The recursion
relations are similar to ones applied at tree level, but contain new
non-trivial features corresponding to poles present for complex momentum
arguments but absent for real momenta. We present the relations and the compact
solutions to them, valid for all n. We also present compact forms for the
previously-computed one-loop n-gluon amplitudes with a single negative helicity
and the rest positive helicity.Comment: 45 pages, revtex, 7 figures, v2 minor correction
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