# Measurement of the $k_\mathrm{t}$ splitting scales in $Z \to \ell\ell$ events in $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

## TL;DR

This paper measures the $k_t$ splitting scales in $Z$ boson events at 8 TeV using ATLAS data, revealing deviations from predictions and providing insights into the transition between perturbative and non-perturbative QCD regimes.

## Contribution

It presents the first detailed measurement of $k_t$ splitting scales in $Z$ events at LHC energies using charged-particle tracks, highlighting discrepancies with theoretical models.

## Key findings

- Data deviates from state-of-the-art predictions in various regions.
- Charged-particle track measurements provide high precision in the transition region.
- Results offer new insights into QCD modeling at the LHC.

## Abstract

A measurement of the splitting scales occuring in the $k_\mathrm{t}$ jet-clustering algorithm is presented for final states containing a $Z$ boson. The measurement is done using 20.2 fb$^{-1}$ of proton-proton collision data collected at a centre-of-mass energy of $\sqrt{s} = 8$ TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on charged-particle track information, which is measured with excellent precision in the $p_\mathrm{T}$ region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.