Studie zur Unterscheidung von Quark- und Gluon-Jets in Ereignissen der Streuung schwacher Eichbosonen W und Z mit dem ATLAS Detektor

The scattering of two leptonically decaying same-sign W bosons is a process of the vector boson scattering (VBS). The largest background of this process are processes with leptonically decaying Z and W bosons. In order to separate the signal from this background the larger fraction of gluon initiated jets in the latter can be used. In this study a quark-gluon tagging tool which uses boosted decision trees as a multivariate approach is investigated by applying it on Monte-Carlo simulations of these processes with a centre-of-mass energy of $\sqrt$ = 13 TeV. As a first step the potential of a perfect quark-gluon tagger is estimated on truth level to gain information about the limits of this approach. If gluon jets can be identified in all $\eta$ regions the significance can be increased by a maximum of 1,3 standard deviations ($\sigma$). In the case that gluon jets can only be separated in the forward region the maximum increase of the significance is 0.89 $\sigma$. With the BDT tool no improvement of the significance can be found. The investigation of a looser phase space does not result in any improvements either.