The default energy calibration of the STAR EEMC (Endcap ElectroMagnetic Calorimeter) uses the energy deposition of minimally ionizing particles (MIPs). An alternate method is to use pi-0's. We are reporting a preliminary proof-of-principle calibration method using pi-0's. This method reconstructs the invariant mass of photon pairs, assumed to be resulting from pi-0 decays, using standard two-body kinematics. When many photon pairs are analyzed, a peak is expected in the resulting invariant mass distribution near the pi-0 mass. Using the measured mass of this peak, and the known mass of the pi-0, a minimization routine adjusts the detector gains to optimize the invariant mass peak of the pi-0. Initial tests suggest that this method is promising.
Barber, Benjamin, "Calibrating the STAR Endcap ElectroMagnetic Calorimeter Using Pi-O’s" (2012). Symposium on Undergraduate Research and Creative Expression (SOURCE). 125.