An experiment on particle and jet production at midrapidity

The aim of this experiment is to search for signatures of Quark-Gluon Plasma (QGP) formation and investigate the behavior of strongly interacting matter at high energy density. Since there is no single accepted signature for the QGP, it is essential to use a flexible detection system at RHIC that can simultaneously measure many experimental observables. The experiment will utilize two aspects of hadron production that are fundamentally new at RHIC: correlations between global observables on an event-by-event basis and the use of hard scattering of partons as a probe of the properties of high density nuclear matter. The event-by-event measurement of global observables--such as temperature, flavor composition, collision geometry, reaction dynamics, and energy or entropy density fluctuations--is possible because of the very high charged particle densities. Event-by-event fluctuations are expected in the vicinity of a phase change, so experiments must be sensitive to threshold-like features in experimental observables as a function of energy density. Full azimuthal coverage with good particle identification and continuous tracking is required to perform these measurements at momenta where the particle yields are maximal. Measurable jet yields at RHIC will allow investigations of hard QCD processes via both highly segmented calorimetry and high pt single particle measurements in a tracking system. A systematic study of particle and jet production will be carried out over a range of colliding nuclei from p + p through Au + Au, over a range of impact parameters from peripheral to central, and over the range of energies available at RHIC. Correlations between observables will be made on an event-by-event basis to isolate potentially interesting event types. In particular, correlations of jet properties with full event reconstruction may lead to some surprising new physics