We congratulate Dr. Viacheslav Tsaran on completing his dissertation entitled
Unified approach to nuclear pion scattering and photoproduction
A promising way to study how protons and neutrons are arranged inside atomic nuclei is by creating neutral pions through photon interactions with the nuclei. However, accurately modeling these interactions has been challenging. This research develops a new theoretical framework for pion production that accounts for the complex interactions between pions and nuclei.
Short summary for scientists:
Advances in understanding atomic nuclei and neutron stars highlight the need for more precise experimental data on neutron distributions in nuclei. Coherent nuclear π0 photoproduction has long been studied as a promising technique for this purpose, yet progress is limited by theoretical challenges, particularly in accurately modeling pion-nucleus interactions. This work seeks to address these issues by developing a unified theoretical framework for nuclear pion photoproduction and scattering, paving the way for more accurate predictions. These developments may also serve as a building block in improving the description of neutrino-induced pion production in view of long-baseline neutrino projects.
We establish our approach by developing an updated model for pion-nucleus scattering in the framework of the distorted wave impulse approximation in momentum space. The scattering amplitude is found from the Lippmann-Schwinger equation for which we construct a novel momentum-space pion-nucleus potential. The developed potential incorporates second-order pion rescattering on intermediate excited nuclear states, in accordance with the Pauli exclusion principle, and involves intermediate pion-nucleon charge exchange and nucleon spin-flip processes. The many-body medium effects are incorporated in the complex effective Δ self-energy, modifying the Δ propagator in the nuclear medium. We estimate three optimal energy-independent parameters of our model by a multi-energy fit of the π±-12C total, reaction, and differential elastic cross sections. To demonstrate the predictive power of our approach, we compare its predictions with π± scattering data on 16O, 28Si, and 40Ca.
Building upon the developed framework for pion-nucleus scattering, we extend our approach to analyze coherent nuclear π0 photoproduction, incorporating final-state charge exchange and nucleon spin flip. The effective Δ self-energy, modifying the photoproduction amplitude, is directly adopted from the analysis of pion-nucleus scattering. The resulting prediction of our approach for nuclear π0 photoproduction aligns well with experimental data for 12C and 40Ca without the need to fit the model parameters of the photoproduction amplitude.
We congratulate Marius Köppel on the completed dissertation entitled
strangeness in neutron stars.
Francesca Bonaiti from the group of Sonia Bacca stands out as one of the top physics PhD students at JGU. Consistently achieving exceptional results in her theoretical research, she has published several papers in peer-reviewed journals. Recognized for her strong potential, she also has collected several invitations to international conferences and has recently secured the prestigious 5-year FRIB theory fellow position in the USA.
