Diffractive Dijet Production in $\sqrt{s} = 7$ TeV $pp$ collisions at the ATLAS Experiment

A data sample of $pp$ collisions with an integrated luminosity of 6.75 nb$^{−1}$ was collected using a combination of a minimum bias trigger and a single jet trigger at $\sqrt{s} = 7$ TeV using the ATLAS detector at the Large Hadron Collider. It is analysed to study diffractive dijet production, i.e. events with a hadronic system containing at least two jets in addition to a large region of pseudorapidity devoid of hadronic activity. The cross section is presented differentially with respect to $\Delta\eta^F$ , the largest continuous region of pseudorapidity which extends from the edge of the detector at = ±4.9 and contains no final state particles above threshold momentum cuts, over the region $0 < \Delta\eta^F < 6.5$. It is also presented differentially in the variable $\xi^±$, which estimates the fractional momentum loss of the proton in single diffractive dissociation ($pp \rightarrow pX$) events. Comparing the data distributions with a Monte Carlo model suggest that fluctuations in the hadronisation process allow non-diffractive dijets to look like diffractive events, but that the data cannot be described solely by non-diffractive dijet production. In addition, the monitoring of the electromagnetic and jet efficiencies for the ATLAS Level-1 Calorimeter Trigger is described.