Analysis into the decays of K+ -> pi+ mu+ mu- and Bc+ -> phi K+ at LHCb

Abstract

This thesis outlines the contributions made by the author to the LHCbPR framework, part of the software validation and testing framework for the LHCb experiment at European Organization for Nuclear Research (CERN), and analyses into the rare decays of $K^{\pm}\rightarrow \pi^{\pm} \mu^+\mu^-$ and $B_c^{\pm}\rightarrow \phi K^{\pm}$ with the LHCb detector. The testing of LHCb software during development is vital to ensuring an efficient and optimal dataflow. LHCbPR allows quick and easy monitoring of the effects of software changes on the system through the orchestrated execution of a set of pre-written tests the results of which are then displayed online. Three such tests, which monitor physics processes during the development of the simulation frameworks, have been migrated by the author from being offline user run scripts to becoming fully automated within LHCbPR. The decay of $K^{\pm}\rightarrow \pi^{\pm} \mu^+\mu^-$, although having been observed previously by other experiments, is investigated within this thesis to determine the prospects of a first observation within a collider experiment, and for the purpose of looking into the prospects of performing a more precise measurement in the future. Analysis is performed making use of the 3.6 $fb^{-1}$ collected from 13 TeV collisions at LHCb between 2015–2017, where additional improvements in triggering have been implemented to record events with lower pT such as those of rare kaon decays. A measurement for the branching ratio of the decay of $B(K^{\pm}\rightarrow \pi^{\pm} \mu^+\mu^-) = (6.3\pm 2.6)\times 10^{-8}$ was recorded, compatible within $1\sigma$ to the world average of $(9.4 \pm 0.6)\times 10^{-8}$. The results, although not yet competitive, hint that with the predicted levels of improvement at LHCb in Run 3, the experiment could indeed contribute to the future of kaon decay measurement