PanScales showers for hadron collisions: all-order validation

We carry out extensive tests of the next-to-leading logarithmic (NLL) accuracy of the PanScales parton showers, as introduced recently for colour-singlet production in hadron collisions. The tests include comparisons to (semi-)analytic NLL calculations of a wide range of hadron-collider observables: the colour-singlet boson transverse momentum distribution; global and non-global hadronic energy flow variables related to jet vetoes and analogues of jettiness distributions; (sub)jet multiplicities; and observables sensitive to the DGLAP evolution of the incoming momentum fractions. In the tests, we also include an implementation of a standard transverse-momentum ordered dipole shower, to establish the size of missing NLL effects in such showers, which, depending on the observable, can reach 100%. This paper, together with [1], constitutes the first step towards process-independent NLL-accurate parton showers for hadronic collisions.

Automated summary

We conducted extensive tests on the NLL accuracy of the PanScales parton showers and compared them with various calculations. The results show that traditional shower simulations have significant NLL errors in some cases.