Diffractive measurements in ATLAS

Measurements made using the ATLAS detector at the LHC at √s = 7 TeV incorporating diffractive processes are presented. A first measurement of the inelastic cross-section using 20 μb^-1 of data is given, yielding a result of σ_inel(ξ>5×10^-6) = 60.3±2.1 mb, for single (pp → Xp) and double (pp → Xp) diffractive processes for a kinematic range corresponding to detector acceptance ξ = M²_X/s calculated from the invariant mass M_X of the heavier dissociation system X. Furthermore a study is made of pseudorapidity gap distributions using 7.1 ± 0.2 μb_-1 of data collected to tune the diffractive fraction of the inelastic cross-section in Monte Carlo (MC) models, and a measurement is made of the differential cross-section for events with large gaps in pseudorapidity where diffractive processes dominate.