## Abstract

In a special run of the LHC with β

σ

The uncertainty in σ

^{⋆}=2.5 km, proton-proton elastic-scattering events were recorded at √s = 13 TeV with an integrated luminosity of 340 μb^{−1}using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from −t=2.5⋅10^{−4}GeV^{2}to −t=0.46 GeV^{2 }using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section σ_{tot}, parameters of the nuclear slope, and the ρ-parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit t→0. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for σ_{tot }and ρ areσ

_{tot(}pp→X)=104.7±1.1mb,ρ=0.098±0.011.The uncertainty in σ

_{tot}is dominated by the luminosity measurement, and in ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.Original language | English |
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Article number | 441 |

Number of pages | 49 |

Journal | European Physical Journal C |

Volume | 83 |

DOIs | |

Publication status | Published - 26 May 2023 |

### Bibliographical note

55 pages in total, 26 figures, 13 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/

## Keywords

- hep-ex