The results of a simple monte carlo simulation of the reaction process are presented here. The simulation requires a hit in one of the forward angled TOF stands (centred at an angle of 18 degrees, 6m downstream from the target). Distributions for this particle are shown by the red histograms. The energy and angle of the other knocked out nucleon (black histogram) are presented for photon energies 250, 350, 450 and 550 MeV. A missing energy distribution is assumed when modelling the reaction.
The setup will also measure the pair momentum distribution up to extremely high momenta. Previous results gave evidence for the effects of short range correlations at high pair momenta. This setup will improve on the sensitivity at high pair momenta by factors of up to 10, as can be seen in the MC simulation of the detection efficiency for events at different pair momenta.
For an Oxygen target it will be important to be able to get some sensitivity to the knockout process from different shell combinations. For a Helium target missing energy resolution is not as important but is needed to separate the 2N processes at low missing energy from FSI processes at higher missing energy.
The energy resolution in TOF is dependent on the velocity and the flight path of the particle. The figures below indicate the expected nucleon energy resolution assuming a timing resolution (sigma) for a TOF bar of 0.3 ns (corresponding to ~0.66ns FWHM). The different lines indicate the results for the flight paths indicated in the key.
The predictions of the Valencia model for a super parallel type geometry are shown below and also as a postscript file. The different processes are stacked in the order 2N (white), 2N+FSI(cross hatch), 3N (red solid), 3N+FSI(red hatch), Npi+ABS(horizontal stripes), Npi+EMIT and NNpi. A 4mm C12 target at an angle of 45 degrees was used. Similar features should be evident for an Oxygen target. Two forward TOF stands centred at +/-7.18 degrees with a flight path of 8m were assumed. The backward angles were covered by TOF stands at a flight path of 2.0m centred at +/- 140 degrees. No limit was placed on the maximum proton energy. The minimum proton energy threshold was equivalent to 5MeV at the TOF bar. It should be noted that the VM assumes an isotropic distribution for the breakup angle of the pair. The predictions for the 2N and 2N+FSI predictions have been increased by a factor 8 to correct for this (as estimated from figure 3 in the proposal). For the phase space survey experiment the pp cross section at low missing energy with the same C12 target as the simulation was ~4.8 and ~2.4 for 200-300 and 300-400 MeV respectively.
