Simon Badger

NGluon: A package to calculate one-loop multi-gluon amplitudes

Abstract We present a computer library for the numerical evaluation of colour-ordered 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 re-evaluation using extended floating point arithmetic. We believe that the library presented here provides an important contribution to future LHC phenomenology. The program may also prove useful in cross checking results obtained by other methods. In addition, the code provides a sample implementation which may serve as a starting point for further developments. Program summary Program title: NGluon Catalogue identifier: AEIZ_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEIZ_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: GNU Public License No. of lines in distributed program, including test data, etc.: 30u2009677 No. of bytes in distributed program, including test data, etc.: 334u2009896 Distribution format: tar.gz Programming language: C++ Computer: Any computer platform supported by the GNU compiler suite. Operating system: No specific requirements – tested on Scientific Linux 5.2. RAM: Depending on the complexity, for realistic applications like 10 gluon production in double precision below 10 MB. Classification: 11.5 External routines: QCDLoop ( http://qcdloop.fnal.gov/ ), qd ( http://crd.lbl.gov/~dhbailey/mpdist/ ) Nature of problem: Evaluation of next-to-leading order corrections for gluon scattering amplitudes in pure gauge theory. Solution method: Purely numerical approach based on tree amplitudes obtained via Berends–Giele recursion combined with unitarity method. Restrictions: Running in double precision the number of gluons should not exceed 14. Running time: Depending on the number of external gluons between less than a millisecond (4 gluons) up to a 1 s (14 gluons) per phase space point.

Numerical evaluation of virtual corrections to multi-jet production in massless QCD

We present a C++ library for the numerical evaluation of one-loop virtual corrections to multi-jet production in massless QCD. The pure gluon primitive amplitudes are evaluated using NGluon (Badger et al., (2011) [62]). A generalized unitarity reduction algorithm is used to construct arbitrary multiplicity fermion–gluon primitive amplitudes. From these basic building blocks the one-loop contribution to the squared matrix element, summed over colour and helicities, is calculated. No approximation in colour is performed. While the primitive amplitudes are given for arbitrary multiplicities, we provide the squared matrix elements only for up to 7 external partons allowing the evaluation of the five jet cross section at next-to-leading order accuracy. The library has been recently successfully applied to four jet production at next-to-leading order in QCD (Badger et al., 2012 [92]).

Hepta-cuts of two-loop scattering amplitudes

A bstractWe present a method for the computation of hepta-cuts of two loop scattering amplitudes. Four dimensional unitarity cuts are used to factorise the integrand onto the product of six tree-level amplitudes evaluated at complex momentum values. Using Gram matrix constraints we derive a general parameterisation of the integrand which can be computed using polynomial fitting techniques. The resulting expression is further reduced to master integrals using conventional integration by parts methods. We consider both planar and non-planar topologies for 2u2009→u20092 scattering processes and apply the method to compute hepta-cut contributions to gluon-gluon scattering in Yang-Mills theory with adjoint fermions and scalars.

Update of the Binoth Les Houches Accord for a standard interface between Monte Carlo tools and one-loop programs

We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.

Physics at a 100 TeV pp collider: Standard Model processes

This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.

QCD corrections to the hadronic production of a heavy quark pair and a W-boson including decay correlations

We perform an analytic calculation of the one-loop amplitude for the W-boson mediated process

A Two-Loop Five-Gluon Helicity Amplitude in QCD

0 to dbar{u}Qbar{Q}bar{ell }ell

NLO QCD corrections to multi-jet production at the LHC with a centre-of-mass energy of s=8 TeV

retaining the mass for the quark Q. The momentum of each of the massive quarks is expressed as the sum of two massless momenta and the corresponding heavy quark spinor is expressed as a sum of two massless spinors. Using a special choice for the heavy quark spinors we obtain analytic expressions for the one-loop amplitudes which are amenable to fast numerical evaluation. The full next-to-leading order (NLO) calculation of hadron + hadron →

An integrand reconstruction method for three-loop amplitudes

Wleft( { to enu } right)bbar{b}

Compact QED tree-level amplitudes from dressed BCFW recursion relations

with massive b-quarks is included in the program MCFM. A comparison is performed with previous published work.