Quality assurance of the VELO modules and analysis of the Bd->K*\mu^+\mu^- rare decay on LHCb

[摘要] The LHCb experiment is a high energy physics detector at the Large Hadron Collider. The experiment has been designed and built to search for new physics in the b hadron sector.This thesis discusses a contribution to the detector construction and preparatory studies for a rare decay analysis.Quality assurance of the silicon modules of LHCb vertex detectorOne of the critical components of the LHCb experiment is the silicon vertex locator (VELO), which is used to measure the decay distance of the $b$-hadrons and is a principal component of the tracking of the experiment. This thesis describes the quality assurance tests of the VELO silicon modules. A facility was designed to operate the VELO modules in vacuum and thermally stress the modules. To verify the suitability of the modules for the experiment a range of studies were performed including measurements of the silicon leakage current and the identification of bad channels through a noise analysis. A full set of 42 modules (and spares) suitable for use in the experiment were successfully tested.Analysis of the $B_d\rightarrow K^* \mu^{+}\mu^{-}$ decayThe $B_d\rightarrow K^* \mu^{+}\mu^{-}$ decay is a flavour changing neutral current process which occurs only via loop diagrams. This is a rare process with a measured branching ratio of \\$\rm 1.10^{+0.29}_{-0.26} \times 10^{-6}$. The $B_d\rightarrow K^* \mu^{+}\mu^{-}$ rare decay is sensitive to new physics (NP) effects. Through the measurement of the so-called forward backward asymmetry distribution a clear signature of NP can be found in this channel.The estimated number of signal events expected per year in LHCb ($\rm 2 fb^-1$) was estimated to be $\rm 7.0\pm0.1\times 10^{3}$. The sensitivity to the zero point of the forward backward asymmetry was calculated as $\rm 0.4~GeV^{2}/c^{4}$, assuming the estimated annual yield. Degradation of the sensitivity due to background events was estimated to be $\rm \sim10-15\%$. Potential systematic effects due to acceptance and background mismeasurement are also presented. The results on the forward backward asymmetry were obtained using a non-parametric unbinned method.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] LHCb, b-physics, VELO, rare decays, FCNC