Measurement of the inelastic pp cross-section at a centre-of-mass energy of √s = 7 TeV

Abstract: The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum p _T> 0.2GeV/c in the pseudorapidity range 2.0 < η < 4.5, is measured by the LHCb experiment at a centre-of-mass energy of √s = 7 TeV. The cross-section in this kinematic range is determined to be σ _inel ^acc = 55.0 ± 2.4 mb with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using Pythia 6, yields σ _inel = 66.9 ± 2.9 ± 4.4 mb, where the first uncertainty is experimental and the second is due to the extrapolation.