1. We are working under the assumption (based on conversations with Brad Swartzky) that the new pipeline based DAQ will be able to handle a 10 -15 kHz trigger rate. Under this assumption only 3 out of the total of 17 kinematics settings will have singles rates that are higher than 15 kHz (4E, 3C and 3F). Only for these 3 settings we will need to inlcude PID in the trigger to bring down the trigger rate to acceptable range. For all other kienamtic settings the PID will be done offline. We will use the HMS aerogel as veto for these 3 settings, other options are to use the preshower and shower counters in the trigger. We have assumed a 95% proton efficeincy for these 3 settings.

2. Based on the experience during E07-002 in Hall-C (which ran with a 1.5 X longer target and a 1.5 x thicker radiator, up to 40 uA of current at 4.1 GeV) we do not expect to need addiotnal shielding. The backgrounds will be more forward angles and the radiation hardness of PbWO4 is much better than lead-glass used in E07-002.  However, if it turns out that we do need addional shielding, the distance between the radiator and target can be increased (from the current 20cm) and then the shielding can be accommodated without any loss of acceptance on the upstream end of the target. The radaitor-target distance can be easily increased to 50cm without any impact on the rastered beam spot size (however, additional cooling for the radiator will be required).

3. The energy threshold for identifying clusters is 1/4 of the elastic 
energy for each kinematic setting. In all cases this is well above 100 MeV. 
The singles rate is the total rate from the DINREG simulation (shown in Fig. 12) divided by the number of crystals (1116).
  

4. The pi0 will be identified from a single photon from the decay, assuming two-body kinematics and using the difference between the epected and measured position of the photon in the calorimeter.  We do not require detection of both photons, thus the two photon acceptance is not relevant.