Measurement of charged-particle event shape variables in √s = 7 TeV proton-proton interactions with the ATLAS detector

The measurement of charged-particle event shape variables is presented in inclusive inelastic pp
collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables
studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state
charged particles’ momentum components perpendicular to the beam direction. Events with at least six
charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the
evolution of each event shape variable as a function of the leading charged-particle transverse momentum,
charged-particle multiplicity, and summed transverse momentum is presented. Predictions from several
Monte Carlo models show significant deviations from data.