Measurement of the total cross section and ρ-parameter from elastic scattering in pp collisions at √s = 13 TeV with the ATLAS detector Aad, G. Aguilar Saavedra, Juan Antonio Rodríguez Chala, Mikael Atlas Collaboration 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 measurement, and in ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude. 2023-06-23T07:57:22Z 2023-06-23T07:57:22Z 2023-05-26 journal article Aad, G., Abbott, B., Abbott, D.C. et al. Measurement of the total cross section and ρ-parameter from elastic scattering in pp collisions at s√=13 TeV with the ATLAS detector. Eur. Phys. J. C 83, 441 (2023). [https://doi.org/10.1140/epjc/s10052-023-11436-8] https://hdl.handle.net/10481/82757 10.1140/epjc/s10052-023-11436-8 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Springer Nature