# Choosing $Z$ particles from a simulator results

I am pretty new to particle Physics. As one of my first projects, I have run a simulation using MadGraph and Delphes. From the simulator result, I am trying to find Z particles produced in the reaction. I am trying to do this by analyzing all possible electron-antielectron, muon-antimuon pairs and the pairs of jets produced to see if they are products of a Z decay. However the invariant mass calculations of the result are over a wide range. I am wondering how do we decide that a pair has origianted from a Z aparticle? What is the range of invariant masses for a Z particle? Is it just 91.1876±0.0021 GeV or is it dependent on some other factors?

I was considering using decay width of Z particle. However I have dropped that idea as the measurements of energy of Z particle are calculated from the Z-decay results and not before the decay. Is this a correct thought process?

Any help is greatly appreciated.

The plus-or-minus figure that you list ($$\pm0.0021\,\mathrm{GeV}$$) is the error on the mean and not the width of the distribution which is very wide.
The 2018 Review gives the total width of the $$Z$$ as $$2.4952\pm0.0023\,\mathrm{GeV}$$.