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Search for rare baryonic b decays with the LHCb experiment at the LHC

McCarthy, James (2016)
Ph.D. thesis, University of Birmingham.

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A search was performed for the Λ\(_b\)\(^0\)→Λ\(^0\)η’ and Λ\(_b\)\(^0\)→Λ\(^0\)η decays with the LHCb experiment. The full dataset recorded by LHCb in 2011 and 2012 is used, corresponding to 1.0fb\(^-\)\(^1\) of proton-proton collision data collected at a centre of mass energy of 7 TeV, and 2.0fb\(^-\)\(^1\) of data collected at a centre of mass energy of 8 TeV, respectively. The B\(^0\)→K\(_S\)\(^0\)η’ decay is used as a normalisation channel, and a selection is designed and optimised using this decay. By measuring the ratio of the branching fractions for the signal decay to the normalisation decay, many systematic uncertainties cancel out. No significant signal is observed for the Λ\(_b\)\(^0\)→Λ\(^0\)η’ decay, and some evidence is observed for the Λ\(_b\)\(^0\)→Λ\(^0\)η decay with a significance of 3σ. The Feldman-Cousins method is used to make the first measurement of the limit on the branching fractions. The limits are
BF(Λ\(_b\)\(^0\)→Λ\(^0\)η’) < 3.1*10\(^-\)\(^6\) at 90% CL.
BF(Λ\(_b\)\(^0\)→Λ\(^0\)η) ε[2.5,22.8]*10\(^-\)\(^6\) at 90% CL.

Type of Work:Ph.D. thesis.
Supervisor(s):Watson, Nigel
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Physics and Astronomy, Particle Physics Group
Subjects:QC Physics
Institution:University of Birmingham
ID Code:6247
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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