Lepton Flavour and Lepton Number Violation searches in charm $D$$_{(s)}^{+}$ → $h$±$l$+$l$∓

The Standard Model is currently thought as the best theory describing the fundamental structure of matter and three of the four fundamental forces, gravity not being included. However, there are a few observations that contradict the predictions it makes, like the asymmetry of matter and antimatter in the Universe, the nature of dark matter and dark energy. Different theoretical models have been proposed to explain these observations and extended searches are made to discover new physics that can validate any of these models. This project is looking for evidence of new physics by studying the decay of the charm $D$$_{(s)}^{+}$ meson into a hadron and a dilepton final state using data that was obtained with the LHCb detector. The majority of these decays are forbidden in the Standard Model because they break two of its symmetries: lepton flavour and lepton number. The project is built on an existing analysis for the same decay channels that set new limits for the branching ratios of 25 out of the 28 decays analysed using data collected in 2015 and 2016. The aim of this project is to improve on that analysis and obtain the final limits for the channels that have not been previously included. The tools used for this improvement will be included in the workflow to analyse these decay channels using data collected in 2017 and 2018 and further improve these limits.