Opened 7 years ago
Last modified 7 years ago
#1259 new How to
Placement of primary vertex and interpretation of IsolationVar
| Reported by: | Soumya | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | |
| Component: | Delphes code | Version: | Delphes 3 |
| Keywords: | Cc: |
Description
Hello,
I am trying to understand how Delphes places the primary vertex of a given event - specifically, is it placed at a fixed location every time or is there some distribution that is sampled to determine where it should fall? And is there any way to configure or change this behavior in Delphes? I ask because when I plot the distribution of the z component of the 3D impact parameters of all muons in one of my samples, it seems quite narrow, which makes me think that I don't understand what's happening with the primary vertex.
I am also uncertain about the interpretation of the IsolationVar attributes for leptons, and am not sure how they are constructed. Do these correspond to relative isolation, i.e. divided by the pT or ET of the lepton itself? Or do I need to construct that from these variables?
Hi,
it depends which configuration you are using.
If you run wihout PileUp, that is, without the PileUpMerger module the vertex is placed where the MC generator places it, usually at the origin.
Be careful on the IP3D, we recently found a bug on the Zd variable. DZ should be fine though.
IsolationVar computes the relative isolation. However in most cards there is already a cut applied on it.