Diffractive Measurements in ATLAS

TL;DR

This paper reports measurements of diffractive processes and the inelastic cross-section in proton-proton collisions at 7 TeV using the ATLAS detector, providing new data to tune theoretical models of diffraction.

Contribution

It presents the first measurement of the inelastic cross-section for specific diffractive processes and studies pseudorapidity gap distributions to improve Monte Carlo models.

Findings

Inelastic cross-section: 60.3 ± 2.1 mb for specific diffractive processes.

Pseudorapidity gap distributions analyzed to tune diffractive fractions.

Differential cross-section measured for events with large pseudorapidity gaps.

Abstract

Measurements made using the ATLAS detector at the LHC at \surd s = 7 TeV incorporating diffractive processes are presented. A first measurement of the inelastic cross-section using 20 \mu b-1 of data is given, yielding a result of {\sigma}inel ({\xi} > 5 \times 10-6) = 60.3 \pm 2.1 mb, for single (p p \rightarrow X p) and double (p p \rightarrow XY) diffractive processes for a kinematic range corresponding to detector acceptance {\xi} = M2X /s calculated from the invariant mass MX of the heavier dissociation system X. Furthermore a study is made of pseudorapidity gap distributions using 7.1 \pm 0.2 \mu b-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.