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 usual source for looking up such basic particle data is the Review of Particle Physics published and maintained by the Particle Data Group. The Review is availble for download and on-line browsing on the PDG website.

The 2018 Review gives the total width of the $Z$ as $2.4952\pm0.0023\,\mathrm{GeV}$.

  • $\begingroup$ Thank you for the explanation and the resource. That gave me a lot of clarity. $\endgroup$ – Sameer Gummuluru Dec 24 '19 at 22:24

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