Dissertation for the degree of doctor rerum naturalium (Dr. rer. nat) to the Faculty of Mathematics and Natural Sciences of the University of Rostock, Germany.
- Thesis (pdf)
- Slides of scientific colloquium (pdf)
- Opening of the doctoral degree procedure: Jun 2020
- Date of scientific colloquium: Nov 2020
- Cite as: doi.org/10.18453/rosdok_id00002802 or CERN-THESIS-2020-217
A search for the rare two-body decays Λb → D°Λ and Ξb° → D°Λ is performed with proton-proton collision data, corresponding to an integrated luminosity of 1/(6 fb), collected by the LHCb experiment at a center-of-mass energy of 13 TeV. The decay Λb → D°Λ is seen with a statistical significance of 5.5 standard deviations, and constitutes the discovery for this decay.
The branching fraction, measured using the Λb → D°pπ decay for normalization, is (Λb → D°Λ) = (9.9 ± 2.3 ± 1.6 ± 1.1) x 1e-6, where the uncertainties are statistical, systematic, and external, respectively. An excess of Ξb° → D°Λ candidates w.r.t. the background is observed with a statistical significance of 1.8 standard deviations and is used to estimate the upper limit f(Ξb°) / f(Λb) x B(Ξb° → D°Λ) / f(Λb → D°Λ) < 0.5 (CL = 95%), where f(Ξb°) / f(Λb) is the ratio of the fragmentation fractions of b-quarks into Ξb° and Λb baryons.