what is happening in this one
why is there no track yet the red and green band show yellow squares?
by Whoandwhatitis moderator
Kind of along the same line as this discussion I just responded to:
A photon will not make tracks in the inner (grey) detectors because it has no charge, but it will leave marks on the electromagnetic calorimeter - the green band.
A neutron also has no charge, so it will not leave tracks on the inner detectors. It is also not absorbed by the electromagnetic calorimeter, so it makes it a bit farther along. It eventually gets slowed down and broken into pieces in the hadron calorimeter - the red band.
See the image(s) here for a visual representation:
This is a very useful comment on what is shown in the picture.
I wanted to add just one extra point about what is not shown in the picture. Any track that points precisely back to the collision point, except for the two muons, is deliberately not shown to make it easier to focus on the tracks from ocvs. So this an extra thing to consider when deciding if the calorimeter energies are due to neutral particle(s)
Oh, I didn't know that about the lines which are not pointing directly back at the collision point other than the muons, not being shown. Does this also apply to white lines which, in normal view, are pointing right at the middle, but which in slice can be seen to be coming from other parts of the beam?
Also please could you say what the scale and resolution of the images in classify is? I'd just like to know what the smallest distance I can reasonably expect to discern is.
Does this mean that if we see a vertex other than the typical two or three muons, it's automatically an off-center vertex, because a center vertex would have been filtered out?
That's useful to know!