Measurement of the Inelastic Proton-Proton Cross Section at $\sqrt{s} = 13$ TeV with the ATLAS Detector at the LHC

TL;DR

This paper reports a measurement of the inelastic proton-proton cross section at 13 TeV using the ATLAS detector, providing data that supports the understanding of proton interactions at high energies and comparing well with theoretical models.

Contribution

First measurement of the inelastic proton-proton cross section at 13 TeV with the ATLAS detector, using forward scintillators for event selection and comparing results with theoretical predictions.

Findings

Measured inelastic cross section in fiducial region: 68.1 ± 1.4 mb

Extrapolated full phase space cross section: 78.1 ± 2.9 mb

Results are consistent with the increase of cross section with energy

Abstract

This Letter presents a measurement of the inelastic proton-proton cross section using 60 $\mu$b$^{-1}$ of $pp$ collisions at a center-of-mass energy $\sqrt{s}$ of $13$ TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region ($2.07<|\eta|<3.86$) of the detector. A cross section of $68.1\pm 1.4$ mb is measured in the fiducial region $\xi=M_X^2/s>10^{-6}$, where $M_X$ is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this $\xi$ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with $M_X>13$ GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated to the full phase space, a cross-section of $78.1 \pm 2.9$ mb is measured, consistent with the inelastic cross section increasing with center-of-mass energy.