Helicity Antenna Showers for Hadron Colliders

Abstract

We present a complete set of helicity-dependent 2->3 antenna functions for QCD initial- and final- state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2->2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226.

25 pages

References in corpus (7)

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• A simple shower and matching algorithm
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• Vector Boson Scattering Processes: Status and Prospects
• Sector Showers for Hadron Collisions
• Collinear Electroweak Radiation in Antenna Parton Showers
• Properties of $g\to b\bar{b}$ at small opening angles in $pp$ collisions with the ATLAS detector at $\sqrt{s}=13$ TeV
• Matching and event-shape NNDL accuracy in parton showers
• Final-state QED Multipole Radiation in Antenna Parton Showers
• Cutoff dependence of the thrust peak position in the dipole shower
• Sudakov evolution without unitarity
• Interleaved Resonance Decays and Electroweak Radiation in Vincia