Measurements of underlying-event properties using neutral and charged particles in pp collisions at $\sqrt{s}=900$ GeV and $\sqrt{s}=7$ TeV with the ATLAS detector at the LHC

We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters. Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point. Particle flows, sensitive to the under- lying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granu- larity. No Monte Carlo generator used in this analysis can accurately describe the measurements. The results are inde- pendent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.