Dijet production in $\sqrt{s}=7$ TeV $pp$ collisions with large rapidity gaps at the ATLAS experiment

TL;DR

This paper analyzes diffractive dijet production in 7 TeV proton-proton collisions at ATLAS, measuring cross sections and estimating the rapidity-gap survival probability, revealing the interplay of diffractive and non-diffractive processes.

Contribution

It provides the first detailed measurement of diffractive dijet production at the LHC, including differential cross sections and the estimation of rapidity-gap survival probability.

Findings

Non-diffractive processes dominate at moderate rapidity gaps.

Diffractive contribution becomes significant at large rapidity gaps and low proton momentum loss.

Rapidity-gap survival probability is estimated from data-model comparisons.

Abstract

A $6.8 \ {\rm nb^{-1}}$ sample of $pp$ collision data collected under low-luminosity conditions at $\sqrt{s} = 7$ TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with $p_\mathrm{T} > 20$ GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in $\Delta\eta^F$, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, $\tilde{\xi}$, of the fractional momentum loss of the proton assuming single diffractive dissociation ($pp \rightarrow pX$). Model comparisons indicate a dominant non-diffractive contribution up to moderately large $\Delta\eta^F$ and small $\tilde{\xi}$, with a diffractive contribution which is significant at the highest $\Delta\eta^F$ and the lowest $\tilde{\xi}$. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions.