Development and validation of HERWIG 7 tunes from CMS underlying-event measurements

TL;DR

This paper develops and validates new parameter sets ('tunes') for the HERWIG 7 event generator, optimized using CMS data across multiple energies, improving the simulation of underlying events in particle collisions.

Contribution

It introduces new HERWIG 7 tunes based on CMS measurements, enhancing the modeling of multiple-parton interactions and color reconnection with different PDF sets.

Findings

Tunes describe CMS data well across energies

Leading-order PDF tunes best match the data

Predictions agree with various collider observables

Abstract

This paper presents a new set of parameters ("tunes") for the underlying-event model of the HERWIG 7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in HERWIG 7, and are obtained from a fit to minimum-bias data collected by the CMS experiment at $\sqrt{s} =$ 0.9, 7, and 13 TeV. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.