Since previously we saw that the data contains back scattering to the EPD, I felt motivated to check whether these EPD pseudo rapidities are from primary(motherless) or secondary(with a mother) hits. 

Here we can see the primary (motherless) particles' pseudo rapidity distribution which hit the EPD:

Secondary (with a mother) particles' pseudo rapidity distribution which hit the EPD:

As it can be seen from the secondary picture, there should be 622380 entries, while we can only see some hundreds of them. Due to this strange thing, I tried to extend the x range of the plot, but did not find any more hits. So I looked deeper, and realised that there are only 168 hits on the secondary plot, while 622212 are missing. With further investigation, I realised that these missing secondary particles have a pseudo rapidity equal to -999. Could this be a default value for unknown pseudo rapidity?

Since in the EPDHijingTree.h header file there is no such thing as eta(pseudo-rapidity) value for the particles coming from Hijing, I calculated it using the following equation:

Where |p| = sqrt(px*px + py*py + pz*pz) and pL = pz.

Moreover, I'm not quite sure how to get the EPD hits' pseudo rapidity, so I did in the following way:

for(int ihit = 0; ihit < T.fEpdHits_; ++ihit)
{
  int trackid = T.fEpdHits_fEpdHitTrackId[ihit];
  double eta = T.fTracks_fEta[trackid];
...
}

So basically, I iterated through the EPDHits, got the trackid from the EPDHit's TrackId, and investigated the corresponding eta for the trackid.

Summary:
  -pseudo rapidity distribution of particles coming from Hijing
  -pseudo rapidity distribution of particles hitting the EPD, for both primary(motherless) and secondary(with a mother) particles
  -There are ~ 600.000 secondary (with a mother) particles hitting the EPD with a pseudo rapidity equal to -999. It's strange, maybe it's a default value for unknown data?
  -Did I calculated the pseudo rapidity in the right way for both the particles coming from Hijing, and for particles hitting the EPD?