Cuts for two-body decays at colliders

Fixed-order perturbative calculations of fiducial cross sections for two-body decay processes at colliders show disturbing sensitivity to unphysically low momentum scales and, in the case of H -> gamma gamma in gluon fusion, poor convergence. Such problems have their origins in an interplay between the behaviour of standard experimental cuts at small transverse momenta (p(t)) and logarithmic perturbative contributions. We illustrate how this interplay leads to a factorially divergent structure in the perturbative series that sets in already from the first orders. We propose simple modifications of fiducial cuts to eliminate their key incriminating characteristic, a linear dependence of the acceptance on the Higgs or Z-boson p(t), replacing it with quadratic dependence. This brings major improvements in the behaviour of the perturbative expansion. More elaborate cuts can achieve an acceptance that is independent of the Higgs p(t) at low p(t), with a variety of consequent advantages.

Automated summary

Fixed-order perturbative calculations for two-body decay processes at colliders exhibit sensitivity to unphysically low momentum scales and poor convergence, especially in the case of H -> γγ in gluon fusion. By making simple modifications to fiducial cuts, such as replacing linear dependence with quadratic dependence, significant improvements in perturbative expansion behavior can be achieved. More sophisticated cuts can even achieve Higgs p(t)-independent acceptance at low p(t) with various advantages.