This is a crude first version of a ttbar analysis plugin for Rivet, to be used at the Lund MCnet school. The code can be downloaded here. This requires a re-write before we can give it to students, and the cuts are completely unoptimised. But it serves as proof of concept. The following plots were generated using Pythia 8.120 to generated inclusive ttbar events at 14 TeV LHC.
A single charged lepton with pT > 30 GeV is required. After this cut the pT spectra of the four leading jets look like this:
Requiring the fourth jet to have pT > 35 GeV we can take the four leading jets to calculate the di-jet and tri-jet masses for all possible combinations. These combinatoric mass plots have a huge background from wrong combinations:
If we take all b-quarks from the event record and match them (dR < 0.5) to jets with pT > 35 GeV (not necessarily the leading four jets, which would probably be a much better choice), we can require exactly two b-jets. That's the spectra of the b-jets:
And the leading two non-b-jets:
Using the two light jets for the W leaves us with just one combination for the W and two combination for the top. The mass plots are nicer, but are still far from being perfect:
Now we apply a mass window cut on the W: 70 GeV < mW < 90 GeV. Then the top peak becomes very clear: