Rapidity gap cross sections measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper measures rapidity gap cross sections in proton-proton collisions at 7 TeV using the ATLAS detector, providing insights into diffractive processes and testing hadronisation models.

Contribution

It presents the first detailed measurement of pseudorapidity gap distributions at 7 TeV, constraining diffractive models and the pomeron intercept in soft diffraction.

Findings

Cross section dσ/dΔηF ~ 1 mb for ΔηF > 3

Data constrain pomeron intercept in triple Regge models

Measurements test hadronisation models at small gap sizes

Abstract

Pseudorapidity gap distributions in proton-proton collisions at sqrt(s) = 7 TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 inverse microbarns. Cross sections are measured differentially in terms of Delta eta F, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at eta = +/- 4.9, in which no final state particles are produced above a transverse momentum threshold p_T Cut. The measurements span the region 0 < Delta eta F < 8 for 200 < p_T Cut < 800 MeV. At small Delta eta F, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process (pp -> Xp), enhanced by double dissociation (pp -> XY) where the invariant mass of the lighter of the two dissociation systems satisfies M_Y <~ 7 GeV. The resulting cross section is d sigma / d Delta eta F ~ 1 mb for Delta eta F >~ 3. The large rapidity gap data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.