eprintid: 25126
rev_number: 15
eprint_status: archive
userid: 3897
dir: disk0/00/02/51/26
datestamp: 2018-07-26 12:51:57
lastmod: 2018-09-04 10:14:36
status_changed: 2018-07-26 12:51:57
type: doctoralThesis
metadata_visibility: show
creators_name: Stahl, Marian
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
subjects: ddc-530
divisions: i-130200
adv_faculty: af-13
cterms_swd: Quantum chromodynamics
cterms_swd: Baryons
cterms_swd: Hadron colliders
cterms_swd: Machine learning
abstract: 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
id_scheme: DOI
id_number: 10.11588/heidok.00025126
ppn_swb: 165566445X
own_urn: urn:nbn:de:bsz:16-heidok-251266
date_accepted: 2018-07-11
advisor: HASH(0x561a62826938)
language: eng
bibsort: STAHLMARIAFIRSTOBSER2018
full_text_status: public
citation:   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]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/25126/1/Lb2LcDzbKm_v1.0.pdf