2,463 research outputs found
Calculation of 1-loop Hexagon Amplitudes in the Yukawa Model
We calculate a class of one-loop six-point amplitudes in the Yukawa model.
The construction of multi-particle amplitudes is done in the string inspired
formalism and compared to the Feynman diagrammatic approach. We show that there
exists a surprisingly efficient way of calculating such amplitudes by using
cyclic identities of kinematic coefficients and discuss in detail cancellation
mechanisms of spurious terms. A collection of formulas which are useful for the
calculation of massless hexagon amplitudes is given.Comment: 15 pages Late
Recursive Approach to One-loop QCD Matrix Elements
We describe the recursive Approach to One-loop QCD Matrix Elements.Comment: 6 pages, to appear in the proceedings of the 7th International
Symposium on Radiative Corrections: Application of Quantum Field Theory to
Phenomenology (RADCOR 2005), Japan, 2-7 Oct 200
Ultra-Violet Infinities and Counterterms in Higher Dimensional Yang-Mills
In this letter we investigate the ultra-violet behaviour of four-point
one-loop gluon amplitudes in dimensions greater than four coupled to various
particles types. We discuss the structure of the counterterms and their
inherent symmetries.Comment: 14 pages, LateX, axodra
Exploiting Twistor Techniques for One-loop QCD Amplitudes
In this talk we describe the recursive Approach to One-loop QCD Matrix
Elements.Comment: Talk presented by David C. Dunbar at Loop and Legs 2006, 5 page
SU(N) group-theory constraints on color-ordered five-point amplitudes at all loop orders
Color-ordered amplitudes for the scattering of n particles in the adjoint
representation of SU(N) gauge theory satisfy constraints arising solely from
group theory. We derive these constraints for n=5 at all loop orders using an
iterative approach. These constraints generalize well-known tree-level and
one-loop group theory relations.Comment: 16 pages, no figures; v2: minor corrections and clarifications,
published versio
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
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
An Integrand Reconstruction Method for Three-Loop Amplitudes
We consider the maximal cut of a three-loop four point function with massless
kinematics. By applying Groebner bases and primary decomposition we develop a
method which extracts all ten propagator master integral coefficients for an
arbitrary triple-box configuration via generalized unitarity cuts. As an
example we present analytic results for the three loop triple-box contribution
to gluon-gluon scattering in Yang-Mills with adjoint fermions and scalars in
terms of three master integrals.Comment: 15 pages, 1 figur
One-Loop n-Point Gauge Theory Amplitudes, Unitarity and Collinear Limits
We present a technique which utilizes unitarity and collinear limits to
construct ansatze for one-loop amplitudes in gauge theory. As an example, we
obtain the one-loop contribution to amplitudes for gluon scattering in
supersymmetric Yang-Mills theory with the helicity configuration of the
Parke-Taylor tree amplitudes. We prove that our ansatz is correct using
general properties of the relevant one-loop -point integrals. We also give
the ``splitting amplitudes'' which govern the collinear behavior of one-loop
helicity amplitudes in gauge theories.Comment: 52 pages (including figures), minor typographical errors corrected,
SLAC-PUB-641
Multiple Singular Emission in Gauge Theories
I derive a class of functions unifying all singular limits for the emission
of a given number of soft or collinear gluons in tree-level gauge-theory
amplitudes. Each function is a generalization of the single-emission antenna
function of ref. [1]. The helicity-summed squares of these functions are thus
also generalizations to multiple singular emission of the Catani--Seymour
dipole factorization function.Comment: Corrections for final journal version (sign in eqn. (6.11), equation
references, typos in indices) & removal of comment about FD
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