Simon Badger

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We present a method for the direct extraction of rational contributions to one-loop scattering amplitudes, missed by standard four-dimensional unitarity techniques. Working in D = 4 − 2ǫ dimensions, we interpret the dependence on the additional dimensions as equivalent to introducing an internal mass. We combine this with the use of generalised unitarity to(More)
We derive general tree-level recursion relations for amplitudes which include massive propagating particles. As an illustration, we apply these recursion relations to scattering amplitudes of gluons coupled to massive scalars. We provide new results for all amplitudes with a pair of scalars and n ≤ 4 gluons. These amplitudes can be used as building blocks(More)
We consider a Higgs boson coupled to gluons via the five-dimensional effective operator HtrGμνG μν produced by considering the heavy top quark limit of the one-loop coupling of Higgs and gluons in the standard model. We treat H as the real part of a complex field φ that couples to the selfdual gluon field strengths and compute the one-loop corrections to(More)
We present MHV-rules for constructing perturbative amplitudes for a Higgs boson and an arbitrary number of partons. We give explicit expressions for amplitudes involving a Higgs and three negative helicity partons and any number of positive helicity partons the NMHV amplitudes. We also present a recursive formulation of MHV rules that incorporates the(More)
We apply the on-shell tree-level recursion relations of Britto, Cachazo, Feng and Witten to a variety of processes involving internal and external massive particles with spin. We show how to construct multi-vector boson currents where one or more off-shell vector bosons couples to a quark pair and number of gluons. We give compact results for single vector(More)
We present a computer library for the numerical evaluation of colourordered n-gluon amplitudes at one-loop order in pure Yang-Mills theory. The library uses the recently developed technique of generalised unitarity. Running in double precision the library yields reliable results for up to 14 gluons with only a small fraction of events requiring a(More)
Background. Several psychometric instruments are available for the diagnostic interview of subjects at ultra high risk (UHR) of psychosis. Their diagnostic comparability is unknown. Methods. All referrals to the OASIS (London) or CAMEO (Cambridgeshire) UHR services from May 13 to Dec 14 were interviewed for a UHR state using both the CAARMS 12/2006 and the(More)
We consider one-loop amplitudes of a Higgs boson coupled to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of a complex field φ that couples to the self-dual field strengths and compute the one-loop corrections to the φNMHV amplitude, which contains one gluon of positive helicity whilst the remaining three have negative(More)