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arXiv · 2610.06698

Polarised cross sections for loop-induced processes with SHERPA+RECOLA

Mareen Hoppe·Marek Schönherr·Frank Siegert
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Abstract

Studying vector boson polarisation has become an integral part of the LHC physics programme in recent years, as it provides an independent test of the electroweak symmetry-breaking mechanism and the gauge sector of the electroweak Standard Model. These measurements require polarised templates from parton-shower Monte Carlo simulations. Their accuracy does not yet meet the precision requirements of upcoming measurements, leading to significant modelling uncertainties in experimental analyses that will constrain the LHC's polarisation sensitivity at latest in the HL-LHC phase. Polarised loop-induced processes have so far not been included in most parton-shower event generators, despite contributing significantly to processes of interest. In this work, we present the extension of the polarisation framework in the Monte Carlo event generator SHERPA to polarised loop-induced processes at fixed LO and LO matched to parton shower. In addition to a description of the methodology based on polarised amplitudes from the RECOLA matrix element generator, we discuss polarisation effects in relevant inclusive, loop-induced processes and their jet-associated counterparts, several of them for the first time. Both the influence of different polarisation definitions and of QCD and QED resummation effects are investigated.

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Mareen Hoppe, Marek Schönherr, Frank Siegert. 2026-10-05. Polarised cross sections for loop-induced processes with SHERPA+RECOLA. https://arxiv.org/abs/2610.06698

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