Baryon-Spectrocopy at BESIII

• Applicant: Professorin Dr. Miriam Fritsch
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456136384

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 experimental. 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 N* and hyperon resonances were taken in photo and electroproduction. Using J/ψ decays to investigate these states provides complementary information which is necessary to shed light on the nature of these states and gives input for theoretical calculations.The goal of this project is the analysis of various meson-nucleon final states in charmonium decays at BESIII. The BESIII experiment has recently multiplied its J/ψ data set by a factor of 8 and reached the number of 10 billion J/ψ events. This unique J/ψ data set gives the opportunity to study excited baryons with high statistics in a completely different environment with respect to photoproduction. Within the SFB1044 project S3 we started to perform the analysis of the two decay channels: J/ψ → p anti-p η and J/ψ → anti-p Σ^+ K_S. The determination of the branching fractions is finished and entered the internal review process at BESIII for the publication of the results. Now, we want to perform a partial wave analysis for these two decay channels. For the interpretation of the experimental data this method is used to determine the baryon resonance properties with minimal model dependence. In addition, we want to investigate the decay channel J/ψ → p anti-p η’. As next step we plan to extend the investigation to the decay channels ψ’ → p anti-p η, ψ’ → anti-p Σ^+ K_S and ψ’ → p anti-p η’ in order to learn more about the differences of the excited ψ’ state in comparison to J/ψ. In parallel, by performing the analysis described above we want to further complete the PWA tool TensorWaves which is based on the machine learning software package TensorFlow.

• DFG Programme: Research Grants