Pulse pile-up recovery for the front-end electronics of the PANDA Electromagnetic Calorimeter

To study the Charmonium spectrum and search for narrow exotic hadronic states, predicted by Quantum Chromodynamics, the PANDA detector will be employed at the future Facility for Antiproton and Ion Research near Darmstadt in Germany. In the PANDA experiment, 1.5 to 15 GeV/c antiprotons will collide with a hydrogen target at average annihilation rates of 20 MHz. One of the most important sub-detectors of PANDA is the Electromagnetic Calorimeter (EMC) planned for the studies of electromagnetic transitions and neutral meson decays. Due to the high annihilation rates, the EMC will be exposed to single-detector hit rates up to 500 kHz, which may lead to pulse overlap. Hence, to recover the energy and time information of the overlapping pulses, the pulse pile-up recovery method is developed. The method is easy to implement in FPGA for online data processing. The Constant Fraction Timing method is applied at the trailing edge to recover the time stamp of pile-up pulses. The energy of pile-up pulses can be recovered up to time differences equal to the pulse rise-time.