# Measurement of distributions sensitive to the underlying event in inclusive $Z$-boson production in pp collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

## TL;DR

This paper measures charged-particle distributions in Z-boson events at 13 TeV with the ATLAS detector, comparing data to Monte Carlo models to evaluate their accuracy in describing the underlying event.

## Contribution

It provides detailed measurements of underlying event-sensitive distributions in Z-boson production at 13 TeV, testing and highlighting discrepancies in Monte Carlo models.

## Key findings

- Monte Carlo models qualitatively agree with data
- Significant discrepancies observed between models and measurements
- Charged-particle multiplicity and transverse momentum distributions characterized

## Abstract

This paper presents measurements of charged-particle distributions sensitive to the properties of the underlying event in events containing a $Z$ boson decaying into a muon pair. The data were obtained using the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 13 TeV with an integrated luminosity of 3.2 fb$^{-1}$. Distributions of the charged-particle multiplicity and of the charged-particle transverse momentum are measured in regions of the azimuth defined relative to the $Z$ boson direction. The measured distributions are compared with the predictions of various Monte Carlo generators which implement different underlying-event models. The Monte Carlo model predictions qualitatively describe the data well, but with some significant discrepancies.