Parton and Jet characterisation of gluonsplittings to heavy quarks in pp collisions using PYTHIA and VINCIA
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Quantum Chromodynamics (QCD) describes the interaction between gluons and quarks, together called partons. Unfortunately the behaviour of the partons cannot be directly measured by a detector. The Quark–Gluon Plasma (QGP), created in high-energy nuclear collisions, can be studied by measuring the remnants of the hard scattered particles. They decay in jets, collimated sprays of particles, which in turn can say something about the initial partons. In this thesis hard scattering events were generated with Pythia8 and Vincia. Different samples with a gluon as the mother particle were compared by filtering light quark splits, charm/beauty quark splits and gluon splits respectively. On parton level one can observe that a mother parton with higher pt is negatively correlated with the angle between its corresponding daughters. For higher ˆpt one can distinguish easier g→q ̄q from g→gg splits using Vincia. For a more evenly distributed pt between daughters a, b in a g→ab split is the angle between the daughters smaller than for less evenly distributed pt. Furthermore the angle between the daughters drops ∼1/z for small z for events in both generators and for the whole z-spectrum only in Pythia8. Also the events generated with Vincia do not obey the LO kernel splittingfunctions for z→0.5.With a jet matching algorithm matched/unmatched jets are distinguished and correlated with the corresponded daughters and mothers using profile plots. On average we see that the matched jet width and the matched jet mass of g→ggsplits is greater than for gluon to quark splits. This means that we can differentiate the two samples from each other by looking at those observables. We observed that the angle between the matched jets and the angle between the corresponding matched daughters is positively correlated. Furthermore in Vincia we observe a ’threshold’ in the transverse momentum of matched daughters for which daughters are found in the same jet. We see that for daughters with pt<75 GeV are on average more found in jets with twice the momentum than daughters with higher pt. At last for higher daughter pt one can conclude that there radiate more particles closely around the daughter than for a daughter with lower pt, since for the latter both the jet width and the jet mass are less.