Particle and jet production in heavy-ion collisions with the ATLAS detector at LHC

Particles and jets produced in heavy ion collisions are used to understand the hot, dense matter created in these interactions. Because of its wide angular coverage, highly hermetic design, and high pT capabilities, the ATLAS detector at the LHC provides an ideal environment in which to study these collisions. ATLAS has measured a wide variety of observables characterizing the bulk medium properties as well as the response of the medium to high-pT probes. Measurements have been made of charged particle multiplicity, elliptic flow, and higher-order particle flow, which allow characterization of global properties of the system. For the first time at this energy, elliptic and higher order flow has been measured over 5 units of pseudorapidity, from -2.5 to 2.5, and over a broad range in transverse momentum, 0.5-20 GeV. The higher-order particle flow studies are providing new insight into the role of initial state geometric fluctuations in these observables, with results obtained for the first through the sixth Fourier coefficient of the azimuthal particle production distribution. A variety of high-pT phenomena have also been studied, such as inclusive charged particle spectra, spectra for single jets and di-jets, and heavy boson interactions. Clear indications of jet quenching are seen, as well as a variety of other observations of the modification of jet properties and of energetic hadron production in the hot and dense QCD medium.