High Speed Data Multiplexer for the Belle II Pixel Detector & Search for an Exotic Resonance at the D*0 anti-D*0 Threshold in Charged B Meson Decays

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LautenbachKlemens_2021_02_08.pdf (94.51 MB)

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2020

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DOI:
http://dx.doi.org/10.22029/jlupub-9840

Abstract

Charmonium spectroscopy has been a vivid field in particle physics since the discovery of the $c$-quark in 1974 as a constituent of the $J/Psi$ meson. Throughout the decades many new resonances with charm quarks have been discovered. In particular, states of a charm quark and an anti-charm quark, called charmonium, fitted well into a level-scheme, comparable to the one of positronium, dependent on the mass and $J^{PC}$ quantum numbers of the discovered state. Until 2003, all new states were already predicted by theory and fit in the assumption of such a bound state, until the Belle Experiment discovered a new, narrow resonance - the $X(3872)$ - in $Brightarrow J/Psi pi^{+}pi^{-}$ decays.Due to the decay mode, in which it was discovered, the $X(3872)$ had clearly charm quarks among its constituents but did not fit into the charmonium level-scheme.For the first time, a resonance, which could only be explained with four quarks as constituents, was observed. The discovery attracted a high level of interest from both, the experimental and theoretical community, and numerous papers trying to explain the nature of that state, and predicting new, likewise states, were published in the following years.New discoveries in the exotic-state regime, like the $Psi(4040)$, $Y(4360)$ and $Y(4660)$, strengthened the theories, which explained those states as real resonance, rather than glue-balls or threshold-effects. In 2013, a first charged state - the $Z_{c}(3900)$ - was discovered and added to the growing level-scheme of charmonia, now including also all the non-predicted but discovered exotic states. One theoretical model, which is nowadays one of the most prominent, describes many of these states as hadronic molecules. A bound state of two Mesons interacting via one-pion exchange. As a consequence of heavy quark spin symmetry, those states would have partner states with higher mass and total angular momentum ($J$). In case of the $X(3872)$, which is close to the $D^{*0}bar{D}^{0}$ threshold, the predicted resonance, which would be a strong argument for the molecular model, is predicted near the $D^{*0}bar{D}^{*0}$ threshold. In this thesis, a simulation of this resonance is performed on Belle II Monte Carlo and the discovery potential for various different width and branching fraction scenarios in three different data sets is estimated. The reconstruction strategy used for the Belle II simulation is then verified on the rediscovery of the $X(3872)$ reference channel in $711~$fb$^{-1}$ of Belle data. At the end of this thesis, the reconstruction is also performed for the $X(4014)$ search on the full Belle data set.

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