title: Search for Lepton Flavour Violation in four-body charm decays at LHCb
creator: Unverzagt, Daniel Joachim
subject: ddc-530
subject: 530 Physics
description: This dissertation presents a search for physics beyond the standard model by the study of lepton flavour violation in four-body charm decays. A search for the decays $D^0 \to \pi^- \pi^+ \mu^\pm e^\mp$ , $D^0 \to K^- \pi^+ \mu^\pm e^\mp$ and $D^0 \to K^- K^+ \mu^\pm e^\mp$ using data collected by the LHCb experiment is performed. These decays provide a unique opportunity to search for new physics in the up-type quark sector, similar to multiple searches performed in the down-type quark sector in other works. The decays are studied using proton-proton collision data corresponding to $6\,fb^{−1}$ of integrated luminosity recorded at a centre-of-mass energy of 13 TeV during the years 2015-2018. An expected upper limit on the branching fraction for these decays is estimated at the order of $10^{−8}$ . Furthermore, separate expected limits for decays with different relative charge constellations in the final dilepton state in respect to the flavour of the $D^0$ meson are reported, providing increased sensitivity to new physics scenarios. It is shown that the current best limit on the branching ratios can be improved by two orders of magnitude with the LHCb dataset. This analysis is performed on a blind dataset with possible $D^0 \to \pi^- \pi^+ \mu^\pm e^\mp$ , $D^0 \to K^- \pi^+ \mu^\pm e^\mp$ and $D^0 \to K^- K^+ \mu^\pm e^\mp$ candidates removed from the dataset. The results are therefore validated by performing an updated measurement of the branching fraction for $D^0 \to \pi^- \pi^+ \mu^- \mu^+$ and $D^0 \to K^- K^+ \mu^- \mu^+$ decays.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/35049/1/ThesisUnverzagt.pdf
identifier: DOI:10.11588/heidok.00035049
identifier: urn:nbn:de:bsz:16-heidok-350490
identifier:   Unverzagt, Daniel Joachim  (2024) Search for Lepton Flavour Violation in four-body charm decays at LHCb.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/35049/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng