I'm looking for events where a W and a Z boson is produced from collision of two protons, with backgrounds coming from top-antitop production, production of 2 Z bosons and Drell-Yann processes (production of 1 Z boson). Selections have been made to reduce these backgrounds (one of those selections check for b-tagged jets and neglects events where one is present to reduce ttbar background, I also ask for 3 leptons which pass my selections).

Plotted here is the number of jets for each of these components (unstacked):

Number of jets distribution unstacked

WZ and DY seem obvious: If you look at leptonic decays you don't expect jets, except those from initial state QCD radiation. But why is there a peak at 1 jet for ZZ production?
Same for ttbar: Not counting the jets coming from the top quarks, we don't expect jets except for initial and final state QCD radiation. Why then does it peak around 1 jet again? Is this just because final state radiation is also possible here in contrast to the case with the other components?

  • $\begingroup$ are this and the other two companion questions for assignment? If not you likely have access to professionals who can very quickly answer your questions. $\endgroup$ – ZeroTheHero Sep 25 '18 at 19:27
  • $\begingroup$ The professionals I have access to are too busy unfortunately... $\endgroup$ – Joshua Sep 25 '18 at 21:03
  • $\begingroup$ One of the reasons monte carlo data is used in analysis in particle physics is because one can answer such questions by checking with monte carlo data. There one can go and look at the basic interactions picked up in the selection that are in the plots where you ask "why". $\endgroup$ – anna v Sep 26 '18 at 3:09
  • $\begingroup$ As a guess for the 1 jet peak for ZZ, I would guess that one of the Z is identified by its γγ decay, and the other is the Z itself from the invariant mass of the bulk. $\endgroup$ – anna v Sep 26 '18 at 3:12

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