Spectroscopy of excited Baryons and Hyperons at BESIII

• Applicant: Professorin Dr. Miriam Fritsch
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558242378

One of the main topics of interest in physics is the composition and structure of matter. Especially for hadrons, which are bound states of quarks and gluons such as the proton and neutron, the description is incomplete. Quantum chromo dynamics (QCD), the theory of the strong interaction, is able to describe most of experimental findings. However, neither QCD nor derived effective theories or lattice-QCD calculations are able to fully explain the rich hadron spectrum. The excitation spectra of hadrons reflect the underlying strong dynamics complementary to polarizabilities, elastic form factors, and parton distributions.Most data concerning nucleon and hyperon resonances (N* and Y*) were taken in photo and electroproduction experiments at energies below 2 GeV. Therefore, only few data exist with hyperons in the final state. The usage of J/ψ decays to investigate N* resonances provides complementary information which is necessary to shed light on the nature of these states and gives input for theoretical calculations. In addition, it widens the mass range for N* resonances and allows the investigation of final states with hyperons and Y* resonances. With the huge BESIII data set of10 billion J/ψ decays, a large number of events is expected for the decays of interest. Due to the large statistics of single decays, coupled channel effects between several decays can be pinned down and used for the interpretation of the data.The goal of this project is to perform coupled channel analyses of various J/ψ decays to baryon-antibaryon-meson final states and extract the pole parameters of the contributing resonances. In the beginning, the two already existing data sets of J/ψ → p pbar η and pbar Σ+ KS (with 2.5 M and 120 k events) will be used for the common interpretation. The focus is to get a proper description of the resonance content of both decay channels by linking the channels together using K matrix formalism. In addition, the decays J/ψ → p pbar η’ and pbar Λ K will be investigated. The influence of the p pbar η’ threshold was already clearly seen in the J/ψ → p pbar η and pbar Σ+ KS data and also in the photo/electroproduction data. N* decays to KΛ were also observed before. Finally, all four decays will be combined for amplitude analysis to further constrain the parameters of the poles of the N* resonances.

• DFG Programme: Research Grants