Particle ID definitions

We have 3 fundamental types of tracks: proton, neutrons and paddle protons. These latter ones are hits on the veto paddles that do not correspond to a track. The presumption is that these are protons that didn't make it any further. Since the hits are within our time window the odds are good for this indeed being the case.

The nDet PID system additionally indicates how the resultant track was chosen in the event of multiple candidates existing. Principle criteria are:

all other things being equal, a proton beats a neutron
a bad Chi2 is only bad if a good one is available (based on threshold parameter ndettrk_chi2cut, probably 5.0)
timing is only bad if someone else has good timing (based on threshold parameter ndettrk_tcut, probably 10ns)
in the end, we want the track with the most probable theta_nq

0 no track

-1 one track and it's bad

-2 one proton and one neutron track, neither used

-3 multiple tracks, all bad/non-proton

1 one track and it's a proton

2 one proton and one or more bad tracks

3 better of 2 proton tracks -- based on theta_nq probability

4 better of 2 proton tracks -- other has bad Chi2

5 better of 2 proton tracks -- other has bad time

8 best track of several is proton -- based on theta_nq probability

9 paddle track

11 one track and it's a neutron

12 only reasonable track is neutron

13 better of 2 neutron tracks -- based on theta_nq probability

14 better of 2 neutron tracks -- other has bad Chi2

15 better of 2 neutron tracks -- other has bad time