2020-11-27 11:00 | 2020-11-27 12:00
Broos Vermeulen, PhD at Nikhef, will defend his thesis 27 november 2020 online at the University of Amsterdam.
Search for production of charginos and neutralinos…
The search performed in this thesis is for the supersymmetric particles called chargino’s and neutralino’s. The process is well-motivated through global fits and is not excluded yet in the case where the mass gap between the chargino and neutralino is small. The process decays into a final state of three leptons and missing energy. The signal is arduous to detect when there is a small mass gap between the supersymmetric particles, as this will result in low momentum leptons and low missing energy. Reconstruction and triggering become difficult in this scenario because there are a lot of different background processes that have similar signatures in the detector. For this reason new identification techniques are used in this thesis to reconstruct leptons that can be classified to result from the signal process. The technique is called the Prompt Lepton Veto and it employs a Boosted Decision Tree, which has been tuned for optimal performance in the analysis.
The sought for supersymmetric models have not been found, making it possible to exclude them. It can be concluded that the following models are excluded: the ones which are enclosed in the region where the mass of the neutralino is 250 GeV and the mass of the chargino is 300 GeV. Although the analysis was not able to find evidence or a discovery of supersymmetry, it was able to exclude a large part of before uncovered phase space.
The search presented in this thesis has been one of the attempts to shed light on questions such as the explanation of dark matter or the desire to unify all forces into a single theory. Although the breakthrough is still keeping us waiting, it is what makes this mature field both challenging and exciting at the moment. It will be with great pleasure when we finally arrive at this breakthrough.
“Search for production of charginos and neutralinos with a small mass gap to the lightest supersymmetric particle with ATLAS at y’s == 13 Te V” (pdf)
The thesis defense will be online and for a limited audience at the Oude Lutherse Kerk of the University of Amsterdam. It is possible to follow the ceremony through a livestream.
Promotor: prof. dr. ir. P.J. de Jong
Co-promotor: dr. S.C. Alderweireldt
contact: Broos Vermeulen
More info on the website of the Universiteit of Amsterdam.
