Measurement of inelastic, single- and double-diffraction cross sections in proton-proton collisions at the LHC with ALICE

Abstract

Measurements of cross sections of inelastic and diffractive processes in proton-proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass M X<200 GeV/c 2) σSD/σINEL = 0.21 ± 0.03, 0.20+0.07-0.08, and 0.20+0.04-0.07, respectively at centre-of-mass energies √s = 0.9, 2.76, and 7TeV; for double diffraction (for a pseudorapidity gap Δη>3) σ DD/σ INEL=0.11±0.03,0.12±0.05, and 0.20+0.05-0.04, respectively at √s = 0.9, 2.76, and 7~\TeV. To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: σINEL = 62.8+2.4-4.0 (model) ±1.2 (lumi) mb at √s = 2.76 TeV and 73.2+2.0-4.6 (model) ±2.6 (lumi) mb at √s = 7 TeV. The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton-antiproton and proton-proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models. © 2013 CERN for the benefit of the ALICE collaboration.