γγγγproduction at the LHC: An application of2→4analytic unitarity

Abstract

We present Next-to-Leading Order (NLO) predictions for γγγγ final states, including the effects of photon fragmentation. Our results are calculated fully analytically using the techniques of Ddimensional unitarity, and we discuss some refinements to existing methods, focusing particularly on the role of three-mass triangle coefficients. Using these techniques we are able to produce a numerically stable Monto Carlo code that runs fully in double precision. We investigate the 4γ signal at colliders, both for Run II of the LHC and at future machines. Our results are implemented in MCFM.

Next-to-leading order predictions forWW+jetproduction

“…This technique allows the amplitude to be represented in a compact analytic form. Similar calculations have provided oneloop amplitudes for a wealth of important processes such as the production of Higgs+2 jets [28][29][30], tt [31], W bb [32], and three- [33] and four-photon production [34]. The implementation of analytic expressions for the virtual contributions addresses both of the issues previously mentioned: it is relatively compact and improves numerical stability.…”

“…The three mass triangle coefficients are most easily expressed in terms of an extended set of momenta that naturally appear in the unitarity approach [25]. For example, the coefficient of the (leading-colour) basis integral I 3 (s 34 …”

Next-to-leading order predictions for WW+jet production

“…This technique allows the amplitude to be represented in a compact analytic form. Similar calculations have provided oneloop amplitudes for a wealth of important processes such as the production of Higgs+2 jets [27][28][29], t t [30], W b b [31], and three- [32] and four-photon production [33]. The implementation of analytic expressions for the virtual contributions addresses both of the issues previously mentioned: it is relatively compact and improves numerical stability.…”