Aad, G.Abbott, B.Abbott, D. C.Abeling, K.Abidi, S. H.Aboulhorma, A.Çetin, Serkant Ali2024-05-192024-05-1920231434-60441434-6052https://doi.org10.1140/epjc/s10052-023-11436-8https://hdl.handle.net/20.500.12713/5888In a special run of the LHC with beta star=2.5 km, proton-proton elastic-scattering events were recorded at root s=13 TeV with an integrated luminosity of 340 mu b(-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 center dot 10(-4) GeV2 to -t=0.46 GeV2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section sigma(tot), parameters of the nuclear slope, and the rho-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 sigma(tot) and rho are sigma(tot) (PP -> X ) =104.7 +/- 1.1 mob , rho=0.098 +/- 0.011. The uncertainty in sigma(tot) is dominated by the luminosity measurement, and in rho by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.eninfo:eu-repo/semantics/openAccessInterferencePolarizationOdderonModelArticle835WOS:0011046299000042-s2.0-85160419394N/A10.1140/epjc/s10052-023-11436-8Q1