title: First observation of the decay $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^{(\ast)0} K^-$ in preparation of a pentaquark search in the $\Lambda_c^+ \bar{D}^{(\ast)0}$ system at the LHCb experiment
creator: Stahl, Marian
subject: ddc-530
subject: 530 Physics
description: This thesis reports the first observation of the decays $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^0 K^-$ and $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^\ast(2007)^0 K^-$ using data corresponding to an  integrated luminosity of 3 fb${}^-1$ collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. A future amplitude  analysis of these $\Lambda_b^0$ decays allows to search the $\Lambda_c^+ \bar{D}^{(\ast)0}$ system for resonant contributions from $P_c^+$ pentaquarks.  Two of which have been discovered in 2015 by the LHCb experiment in the J/$\psi p$ system.  Observing $P_c^+$ pentaquarks in the $\Lambda_c^+ \bar{D}^{(\ast)0}$ system would allow for further insight to the nature of these resonances.    In addition, the measurement of the $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^0 K^-$ and $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^\ast(2007)^0 K^-$ branching fractions relative to the decay $\Lb\to\Lc\Dsm$ is  made, resulting in   \begin{alignat}{1}  \frac{\mathscr{B}(\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^0 K^-)}{\mathscr{B}(\Lambda_b^0 \rightarrow \Lambda_c^+ D_s^-)} &= \left(14.04 \pm 0.58 \pm 0.33 \pm 0.45 \right)\,\% \nonumber \\  \frac{\mathscr{B}(\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^\ast(2007)^0 K^-)}{\mathscr{B}(\Lambda_b^0 \rightarrow \Lambda_c^+ D_s^-)}  &= \left(43.5 \pm 1.4 {}^{+1.2}_{-0.8} \pm 1.4 \right)\,\% \nonumber   \end{alignat}  The first uncertainty is statistical, the second systematic and the third is due to the knowledge  of the branching fractions of $D_s^- \rightarrow K^- K^+ \pi^-$ and $\bar{D}^0 \rightarrow K^+ \pi^-$. It is shown that the obtained result agrees with previously measured $B\rightarrow  D\bar{D}^{(\ast)0} K^-$ branching fractions, as expected from the lowest order approximation of QCD factorisation.    The developed methods are integral components of the future amplitude analysis of $\LbLcDzbstK$. These and further algorithms presented here were developed in  a modularised way to be applied to a variety of analyses at \lhcb, in particular pentaquark searches.
date: 2018
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/25126/1/Lb2LcDzbKm_v1.0.pdf
identifier: DOI:10.11588/heidok.00025126
identifier: urn:nbn:de:bsz:16-heidok-251266
identifier:   Stahl, Marian  (2018) First observation of the decay $\Lambda_b^0 \rightarrow \Lambda_c^+ \bar{D}^{(\ast)0} K^-$ in preparation of a pentaquark search in the $\Lambda_c^+ \bar{D}^{(\ast)0}$ system at the LHCb experiment.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/25126/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng