Measurement of event shapes at large momentum transfer with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper presents measurements of event shape variables in high-energy proton-proton collisions at 7 TeV using the ATLAS detector, comparing results to Monte Carlo predictions and analyzing their dependence on jet momentum.

Contribution

It provides the first detailed comparison of event shape variables at large momentum transfer with various Monte Carlo models in pp collisions at 7 TeV.

Findings

Event shape variables are generally well described by models.

Measurements as a function of jet momentum show consistent behavior.

Third-jet resolution, aplanarity, thrust, sphericity, and transverse sphericity are effectively measured.

Abstract

A measurement of event shape variables is presented for large momentum transfer proton-proton collisions using the ATLAS detector at the Large Hadron Collider. Six event shape variables calculated using hadronic jets are studied in inclusive multi-jet events in 35 pb^-1 of integrated luminosity at a center-of-mass energy of sqrt(s) = 7 TeV. These measurements are compared to predictions by three Monte Carlo event generators containing leading-logarithmic parton showers matched to leading order matrix elements for 2 to 2 and 2 to n (n=2,...6) scattering. Measurements of the third-jet resolution parameter, aplanarity, thrust, sphericity, and transverse sphericity are generally well described. The mean value of each event shape variable is evaluated as a function of the average momentum of the two leading jets pT1 and pT2, with a mean pT approaching 1 TeV.