How Delphes deals with secondary vertices

[Pavel Demin]

Moving comment 7 from ticket #138 to a separate ticket:

can Delphes recognize particles coming from secondary vertices even if the second vertex is out of tracker? I mean, if I have some vertices in the tracker and some others out of it, will Delphes do the same analysis? How does it deal with this scenario?

[Pavel Demin]

Normally, each track has coordinates of its production vertex (Track.X, Track.Y, Track.Z). So, selecting Tracks with coordinates that are not (0,0,0), you'll have coordinates of all displaced vertexes. Do you think it would help your analysis?

[Pavel Demin]

Normally we have the following expression in the ParticlePropagator module (modules/ParticlePropagator.cc):

    // check that particle position is inside the cylinder
    if(TMath::Hypot(x, y) > fRadius || TMath::Abs(z) > fHalfLength)
    {
      continue;
    }

So, the particles originating from a vertex outside of the tracker (defined as a cylinder) are not recognized as tracks and are not propagated to the edge of the tracker volume. It means that these particles are completely ignored.

But the idea of Delphes is that nothing is carved in stone: it provides some default behavior that could be easily adapted by the users to their requirements.

So, if you have an idea of how the displaced vertex should be treated you can

• either try to adapt the ParticlePropagator module (and eventually other modules and classes) to your requirements
• or try to explain us your requirements and then we'll try to help you to modify Delphes