Measurement of the energy density as a function of pseudorapidity in proton–proton collisions at √ s = 13 TeV

Abstract

A measurement of the energy density in proton– proton collisions at a centre-of-mass energy of √ s = 13 TeV is presented. The data have been recorded with the CMS experiment at the LHC during low luminosity operations in 2015. The energy density is studied as a function of pseudo- rapidity in the ranges − 6 . 6 <η< − 5 . 2 and 3 . 15 < | η | < 5 . 20. The results are compared with the predictions of several models. All the models considered suggest a different shape of the pseudorapidity dependence compared to that observed in the data. A comparison with LHC proton–proton collision data at √ s = 0 . 9 and 7 TeV confirms the compatibility of the data with the hypothesis of limiting fragmentation.