Event Reconstruction

The raw data are processed offline to produce data summaries of the events, which are later used in various physics analyses. When reconstructing particle tracks in the central arms [20], a track model primarily based on DC and PC1 information is utilized. Trajectories and momenta are reconstructed using a field-integral to account for the non-uniform magnetic field. Fig. 2.2 shows Drift Chamber hits that are used to reconstruct a track.

Figure 2.2: A charged track passing through one of the Drift Chambers. The open circles show the detector hits. ($X_1$ and $X_2$ are two sets of wire planes inside the DC.)

The sign of the inclination angle $\alpha$ determines the charge of the particle, and information on the longitudinal motion is received from the PC1 $z$ coordinate. When the trajectory is determined, its projected intersections with various detectors are recorded in order to facilitate inter-detector hit association.

Simulated events are reconstructed using the same code with minor modifications. The simulated data files are produced using an event generator, such as RQMD [21] or Hijing [22]. The output from the event generator is fed into a simulation package for PHENIX, called PISA (PHENIX Integrated Simulation Application), which is based on GEANT [23]. Specific code has been developed to simulate the response for each detector.