Abstract

We present an extension of the GENEVA Monte Carlo framework to include multiple parton interactions (MPI) provided by PYTHIA8. This allows us to obtain predictions for underlying-event sensitive measurements in Drell-Yan production, in conjunction with GENEVA's fully-differential NNLO calculation, NNLL' resummation for the 0-jet resolution variable (beam thrust), and NLL resummation for the 1-jet resolution variable. We describe the interface with the parton shower algorithm and MPI model of PYTHIA8, which preserves both the precision of partonic N-jet cross sections in GENEVA as well as the shower accuracy and good description of soft hadronic physics of PYTHIA8. We present results for several underlying-event sensitive observables and compare to data from ATLAS and CMS as well as to standalone PYTHIA8 predictions. This includes a comparison with the recent ATLAS measurement of the beam thrust spectrum, which provides a potential avenue to fully disentangle the physical effects from the primary hard interaction, primary soft radiation, multiple parton interactions, and nonperturbative hadronization.

Highlights

  • Exclusive Monte–Carlo event generators are an important tool to make theoretical predictions for collider observables

  • We have presented a study of underlying event (UE)-sensitive observables for Drell–Yan neutral-current production in the Geneva Monte Carlo framework

  • By adding the ability to turn on the multiple parton interactions (MPI) model included in Pythia8, one obtains an accurate description of observables that are sensitive to both hard and soft physics

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Summary

Introduction

Exclusive Monte–Carlo event generators are an important tool to make theoretical predictions for collider observables. There have been many efforts to combine precision calculations of the hard interaction with fully exclusive Monte Carlo generators, which aim to describe the perturbative evolution of the primary partons and add nonperturbative physics and MPI effects through physical models. This started with the combination of leading-order (LO) predictions for several multiplicities with parton showers [8,9], and shortly thereafter methods to combine next-to-leading order (NLO) calculations were developed [10,11,12,13,14].

Review of GENEVA and its PYTHIA8 interface
The partonic calculation
Interface to the parton shower
Interface to multiple parton interactions
Comparison with ATLAS and CMS data
Beam thrust event shape
Conclusions
Full Text
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