Current detectors used in particle accelerators are not able to detect neutrinos. Due to this, studying processes with neutrinos in high energy physics experiments is not as trivial as processes with detectable objects. A deeper understanding of neutrino processes is necessary for pushing the limits of the Standard Model of particle physics. The aim of this research is to evaluate the decay of the Z boson, one of the weak-interaction mediating particles, to neutrinos.
To get the events with Z boson decay to neutrinos, the process $pp \to \ell \bar{\ell} \nu \bar{\nu}$ is generated with MG5_aMC@NLO (MadGraph) [1] event generator to simulate proton-proton collisions in a collider. The process is dominated by lowest order diagrams. Of these, one is the signal process, out of five major backgrounds the two are mostly negligible (cross sections are tiny). Using the event information provided by the event generator, it is possible to split the events into signal and background. The use of physically observable quantities (like invariant mass, $p_T$, etc.) is necessary for analysis of real processes seen in nature. For unaltered data, the signal cannot be isolated, due to the background processes being more frequent. Cuts on the data are made around Z boson mass to help isolate the signal. Fully isolating the signal from background processes both from reducible and irreducible backgrounds is the ultimate aim of this research.
This research is one of the few attempts to directly study neutrino processes in collider-based experiments. Findings gathered from this or similar experiments can lead to a validation of the Standard Model in the lepton sector, possibly opening a door for Beyond the Standard Model physics.