# Measurement of the four-lepton invariant mass spectrum in 13 TeV proton-proton collisions with the ATLAS detector

## TL;DR

This paper measures the four-lepton invariant mass spectrum in 13 TeV proton-proton collisions using the ATLAS detector, providing detailed data that tests Standard Model predictions and searches for signs of new physics.

## Contribution

It presents the first detailed measurement of the four-lepton invariant mass spectrum at 13 TeV, comparing results with advanced Standard Model calculations and constraining potential new physics contributions.

## Key findings

- Measured differential cross-section across various mass regions.
- Observed consistency with Standard Model predictions.
- Placed limits on beyond Standard Model contributions.

## Abstract

A measurement of the four-lepton invariant mass spectrum is made with the ATLAS detector, using an integrated luminosity of 36.1 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}$ = 13 TeV delivered by the Large Hadron Collider. The differential cross-section is measured for events containing two same-flavour opposite-sign lepton pairs. It exhibits a rich structure, with different mass regions dominated in the Standard Model by single $Z$ boson production, Higgs boson production, and $Z$ boson pair production, and non-negligible interference effects at high invariant masses. The measurement is compared with state-of-the-art Standard Model calculations, which are found to be consistent with the data. These calculations are used to interpret the data in terms of $gg\rightarrow ZZ \rightarrow 4\ell$ and $Z \rightarrow 4\ell$ subprocesses, and to place constraints on a possible contribution from physics beyond the Standard Model.