Logarithmically-accurate and positive-defnite NLO shower matching

Abstract

We present methods to achieve NLL+NLO accurate parton showering for processes with two coloured legs: neutral- and charged-current Drell-Yan, and Higgs production in pp collisions, as well as DIS and e +e − to jets. The methods include adaptations of existing approaches, as well as a new NLO matching scheme, ESME, that is positive-defnite by construction. Our implementations of the methods within the PanScales framework yield highly competitive NLO event generation speeds. We validate the fxed-order and combined resummation accuracy with tests in the limit of small QCD coupling and briefy touch on phenomenological comparisons to standard NLO results and to Drell-Yan data. The progress reported here is an essential step towards showers with logarithmic accuracy beyond NLL for processes with incoming hadrons.