Measurement of the total cross section and $$\rho $$ ρ -parameter from elastic scattering in pp collisions at $$\sqrt{s}=13$$ s = 13 TeV with the ATLAS detector
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2023
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Abstract
In a special run of the LHC with β =2.5km, 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 Mandelstamt variable in the range from−t =2.5·10−4GeV2 to−t =0.46GeV2 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 thet-dependence. The results for σtot and ρare σtot(pp→X)=104.7±1.1mb, ρ=0.098±0.011. The uncertain tyinσtot is dominated by the luminosity measurement, and in ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.
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The European Physical Journal C. 2023 May 26;83(5):441