A Measurement of the Radiation Environment Around Prompt J/ψ Events at ATLAS

Abstract

The J/ψ particle has been the source of much research since itsdiscovery in 1974. It provides an important probe of quantumchromodynamics and has lead to many important insights into theinteractions of quarks and gluons in bound states. The rate of J/ψproduction was found to be much higher than expected at hadroncolliding experiments. Non-relativistic quantum chromodynamics wasdeveloped in order to address these issues. This theory predicts astrong spin-alignment not observed in data. All previous measurementsof J/ψ production have overlooked the hadronic environment theJ/ψ is produced in. This work is the first exploration of theradiation surrounding J/ψ events measured at ATLAS at√s=8 TeV. This is the first measurement of theseparation between the J/ψ and a matched jet and the secondmeasurement of the momentum fraction shared between the jet and theJ/ψ. These variables probe the radiation environment around theJ/ψ, and provide a new ways to understand quarkonia production.