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The rare decay of \(\Lambda\)\(_b\) \(\rightarrow\) \(\Lambda\)\(^0\)\(\mu\)\(^+\)\(\mu\)\(^-\) with the LHCb detector at CERN

Elsby, Daniel (2013)
M.Phil. thesis, University of Birmingham.

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The LHCb detector, one of the main particle physics detectors at the Large Hadron Collider (LHC) is purpose built for the study of interesting and rare particle physics events. One such rare event with an expected branching ratio of≈ 10\(^-\)\(^6\) is the decay of \(\Lambda\)\(_b\) \(\rightarrow\) \(\Lambda\)\(^0\)\(\mu\)\(^+\)\(\mu\)\(^-\). This decay is interesting since it offers an opportunity to test our current understanding of particle physics and search for signs of new physics. In this thesis the background theory to the current model of particle physics (the Standard Model) and the main operational properties of the LHCb detector are summarized. The feasibility of observing this decay with LHCb is investigated and an estimated yield is calculated. A cut based selection is developed and optimized in order to select events according to this decay from the 2010 data set of approximately 1fb\(^-\)\(^1\) at a centre of mass energy of 7TeV. A clear indication of the decay is seen in the data with approximately 100 signal events and a significance of 4.8\(\sigma\). The calculations of all required efficiencies are tabulated and are used to calculate a relative branching ratio to the resonant decay of \(\Lambda\)\(_b\)\(\rightarrow\)\(\Lambda\)\(^0\)J/\(\psi\), where J/\(\psi\)\(\rightarrow\)\(\mu\)\(^+\)\(\mu\)\(^-\), of \(\mathcal{R}\) = 1.89 x 10\(^-\)\(^3\).

Type of Work:M.Phil. thesis.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Physics and Astronomy
Subjects:QA Mathematics
QB Astronomy
Institution:University of Birmingham
ID Code:4020
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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