-- RainerNovotny - 26 Apr 2006

Possibilities of the EM-Calorimeter to contribute to PID

The EM-Calorimeter, based on PWO crystals, provides in case of optimum read-out capabilities a good energy resolution for particles and photons (light quenching for MIPS ~ 1], time information well below 1ns above an energy deposition of > 100 MeV (might be even further improved) and position information due to the fine granularity of the calorimeter (single crstal front face ~ 2cm x 2cm) and a reconstruction of the impact point in case of shower formation (resolution ~ 1-2mm).

The following aspects for PID could be considered:

• energy measurement: in case of low energies (<400MeV for protons) the full energy can be deposited in 200mm of PWO, therefore complementary to tracking. It could be even used to measure the low energy part of muons.
• PID: the correlation with an energy deposition in the plastic-TOF-barrel could be used to some extend as a telesope for energy-loss/energy correlations (for sure for low energy particles).
• shower and hit pattern: the large difference of the hit pattern of responding detector elements near the point of impact will allow to discriminate or identify particles (low multiplicity) and photons/electrons. It could, for example, be used to discriminate between photons and pions. In addition, the reconstracted point of impact can be correlated with the tracking information.
• time information: The present data with APD read-out but very preliminary read-out circuits have shown aready the capabilities of sub-nanosecond timing. One can consider time resolutions below 1ns even at 50 - 100MeV and values well below 400ps above 500MeV. These resolutions are not sufficient for TOF due to the short target-detector distance but allow time correlations with tracking or the DIRC. In addition, it can provide an excellent tool to discriminate background caused by different interaction points etc.