Measurement of distributions sensitive to the underlying event in inclusive Z-boson production in $pp$ collisions at $\sqrt{s}=7$ TeV with the ATLAS detector

TL;DR

This paper measures charged-particle distributions related to the underlying event in Z-boson production at 7 TeV proton-proton collisions, comparing data with Monte Carlo models to improve understanding of underlying event dynamics.

Contribution

It provides the first detailed measurement of underlying event-sensitive distributions in Z-boson events at the LHC, aiding in tuning Monte Carlo models.

Findings

Distributions of charged-particle multiplicity and transverse momentum are measured.

Data shows differences from Monte Carlo predictions, highlighting areas for model improvement.

Results help refine underlying event modeling in high-energy proton-proton collisions.

Abstract

A measurement of charged-particle distributions sensitive to the properties of the underlying event is presented for an inclusive sample of events containing a Z-boson , decaying to an electron or muon pair. The measurement is based on data collected using the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of $4.6$ fb$^{-1}$. Distributions of the charged particle multiplicity and of the charged particle transverse momentum are measured in regions of azimuthal angle defined with respect to the Z-boson direction. The measured distributions are compared to similar distributions measured in jet events, and to the predictions of various Monte Carlo generators implementing different underlying event models.