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## Abstract / Description of output

In a special run of the LHC with β ∗ = 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 GeV2 to −t = 0.46 GeV2 using 6.9 million elastic-scattering

candidates. This paper presents measurements of the total cross section σtot , 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 σtot and ρ are σtot( pp → X) = 104.7 ± 1.1 mb, ρ = 0.098 ± 0.011. The uncertainty in σtot is dominated by the luminosity mea-

surement, and in ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.

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 GeV2 to −t = 0.46 GeV2 using 6.9 million elastic-scattering

candidates. This paper presents measurements of the total cross section σtot , 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 σtot and ρ are σtot( pp → X) = 104.7 ± 1.1 mb, ρ = 0.098 ± 0.011. The uncertainty in σtot is dominated by the luminosity mea-

surement, 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 |

Pages (from-to) | 1-49 |

Number of pages | 49 |

Journal | The European Physical Journal C |

Volume | 83 |

Issue number | 5 |

DOIs | |

Publication status | Published - 26 May 2023 |

## Keywords / Materials (for Non-textual outputs)

- INTERFERENCE
- POLARIZATION
- ODDERON
- MODEL