B_{s}^{0}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-} decays in the LHCb detector, and a study of radiation damage in the Vertex Locator

Pritchard, Adrian
B_{s}^{0}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-} decays in the LHCb detector, and a study of radiation damage in the Vertex Locator. PhD thesis, University of Liverpool.

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The Large Hadron Collider (LHC) is currently the highest energy particle accelerator in the world, and is designed to collide protons at a centre-of-mass energy up to 14TeV. The LHCb experiment is one of four main experiments situated on the LHC ring, and is designed for making precision measurements of the decays of particles containing a b quark. In order to perform these measurements, it is necessary to precisely measure production and decay vertices in the collisions, and LHCb makes use of the Vertex Locator (VELO) to do this. The need for the VELO to be very close to the proton collision point requires it to be able to withstand high levels of radiation. This thesis presents studies of the damage suffered by the VELO during the full first run period of the LHC, with comparisons to the predicted levels of damage. It is observed that the VELO is performing well despite the radiation damage, and should continue to do so until the planned end of its operation. This thesis also presents the full analysis of the measurement of the branching fraction of the B_{s}^{0}\rightarrow~D_{s}^{(\ast)+}D_{s}^{(\ast)-} decay. This measurement is of interest theoretically as it may provide information about B_{s} oscillations, a phenomenon where B_{s} mesons spontaneously change to their anti-B_{s} anti-matter counterpart, and back. The analysis is performed on the full LHCb 2011 data set, consisting of approximately 1.1fb-1 of proton-proton collisions at centre-of-mass energy of 7TeV. The branching fraction is measured relative to the decay B^{0}\rightarrow D_{s}^{+}D^{-} in order to reduce the systematic uncertainty on the result, and is found to be: \BF(B_{s}^{0}\rightarrow~D_{s}^{(\ast)+}D_{s}^{(\ast)-}) = (3.07 \pm 0.10 (stat.) \pm 0.23 (sys.) \pm 0.34 (norm.))\%. This result is consistent with, and more precise than, all previous experimental determinations, and also the theoretical prediction.

Item Type: Thesis (PhD)
Additional Information: Date: 2015-10-22 (completed)
Subjects: ?? QC ??
Depositing User: Symplectic Admin
Date Deposited: 17 Dec 2015 10:32
Last Modified: 17 Dec 2022 01:05
DOI: 10.17638/02034099
URI: https://livrepository.liverpool.ac.uk/id/eprint/2034099