Disputation: Exploring the Merits and Challenges of Hyperon Physics: with PANDA at FAIR

  • Date:
  • Location: Ångströmlaboratoriet, Lägerhyddsvägen 1 Häggsalen
  • Doctoral student: Walter Ikegami Andersson
  • Contact person: Walter Ikegami Andersson
  • Disputation

Binary hyperon production in antiproton-proton annihilations will be carried out with the PANDA experiment at FAIR, and probes the strong interaction in the non-perturbative regime where the relevant degrees of freedom are unclear. The self-analyzing decays of hyperons provide a straightforward way to study reaction dynamics via the measurement of spin observables. However, since weakly decaying hyperons can travel several centimeters before decaying, they are challenging to reconstruct. Conventional track reconstruction algorithms assume that charge particles originate in the experiment interaction point.

In this thesis, software tools are developed for the reconstruction and fitting of charged particles in the collaboration-wide software package PandaRoot. Pattern recognition algorithms are developed for the reconstruction of charged particle tracks with displaced vertices. Three algorithms that reconstruct the longitudinal momentum in the Straw Tube Tracker (STT) of PANDA are developed. They are based on a combinatorial approach, a Hough Transform, and a recursive annealing fit. The implementation and performance of these algorithms are presented. The track fitting scheme of PandaRoot is overhauled to treat the five particle species that PANDA is expected to measure, namely electrons, muons, pions, kaons and protons. The new track fitting scheme is outlined and discussed.

When the PANDA experiment is taken into operation, beam time will be allocated to many different measurements. For this reason, feasibility studies are performed in this thesis. The pp → ΛΛ reaction is simulated at 1.642 GeV/c and the pp → Ξ+Ξ− reaction is simulated at 7.0 and 4.6 GeV/c beam momenta. The simulation and analysis chain of the studies are explained. Expected reconstruction rates are presented. Furthermore, the feasibility of reconstructing spin observables in the reactions is discussed.