[Paper Review] PANDORA project: photo-nuclear reactions below $A=60$

A. Tamii, L. Pellegri+79 more|arXiv (Cornell University)|Nov 8, 2022

Nuclear physics research studies4 references4 citations

TL;DR

The PANDORA project investigates photo-nuclear reactions in light nuclei (A < 60) using virtual-photon excitation via proton scattering and real-photon absorption with laser Compton scattering γ-beams to measure photo-absorption cross sections and decay branching ratios. It integrates advanced nuclear models and TALYS reaction code to reduce uncertainties and enable astrophysical simulations of ultra-high-energy cosmic ray propagation.

ABSTRACT

Photo-nuclear reactions of light nuclei below a mass of $A=60$ are studied experimentally and theoretically by the PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project. Two experimental methods, virtual-photon excitation by proton scattering and real-photo absorption by a high-brilliance gamma-ray beam produced by laser Compton scattering, will be applied to measure the photo-absorption cross sections and the decay branching ratio of each decay channel as a function of the photon energy. Several nuclear models, e.g. anti-symmetrized molecular dynamics, mean-field type models, a large-scale shell model, and ab initio models, will be employed to predict the photo-nuclear reactions. The uncertainty in the model predictions will be evaluated from the discrepancies between the model predictions and the experimental data. The data and the predictions will be implemented in a general reaction calculation code TALYS . The results will be applied to the simulation of the photo-disintegration process of ultra-high-energy cosmic rays in inter-galactic propagation.

Motivation & Objective

• To systematically measure photo-absorption cross sections and decay branching ratios for light nuclei (A < 60) across a range of photon energies.
• To reduce uncertainties in theoretical predictions of photo-nuclear reactions by comparing model outputs with high-precision experimental data.
• To implement experimental and theoretical results into the TALYS reaction code for broader applications in astrophysics and nuclear technology.
• To study the photo-disintegration of ultra-high-energy cosmic rays during inter-galactic propagation using improved nuclear reaction inputs.
• To support applications in nuclear astrophysics, radiation safety, medical isotope production, and lightning physics through precise reaction data.

Proposed method

• Employ virtual-photon excitation via proton scattering on light nuclei to probe photo-reaction strength functions indirectly.
• Use high-brilliance γ-rays produced by laser Compton scattering at facilities like RCNP, iThemba LABS, and ELI-NP to perform direct real-photon absorption measurements.
• Measure photo-absorption cross sections and decay branching ratios (e.g., (γ,n), (γ,p), (γ,2n)) as functions of incident photon energy.
• Apply multiple theoretical models: anti-symmetrized molecular dynamics (AMD), mean-field models, large-scale shell model, and no-core shell model (NCSM) for predictions.
• Quantify model uncertainties by comparing predictions against experimental data and feed discrepancies into TALYS for improved reaction modeling.
• Integrate all experimental and theoretical data into the TALYS reaction code for use in astrophysical and technological simulations.

Experimental results

Research questions

• RQ1 What are the precise photo-absorption cross sections and decay branching ratios for light nuclei (A < 60) as a function of photon energy?
• RQ2 How do different nuclear models (AMD, mean-field, shell model, ab initio NCSM) predict photo-nuclear reaction rates, and what are their systematic uncertainties?
• RQ3 To what extent do experimental data from proton scattering and laser Compton γ-beams resolve discrepancies between theoretical predictions and existing data?
• RQ4 How do improved nuclear reaction inputs affect the simulation of ultra-high-energy cosmic ray photo-disintegration in inter-galactic space?
• RQ5 What is the role of photo-nuclear reactions in atmospheric lightning-induced γ-ray emission and positron production?

Key findings

• The PANDORA project plans to measure photo-nuclear reaction data for light nuclei (A < 60) using two complementary experimental techniques: proton scattering and laser Compton γ-beams.
• First beam times for nuclear physics experiments are scheduled for 2022 at RCNP and 2023 at iThemba LABS, with initial commissioning of the LCS γ-beam facility at ELI-NP by end of 2023.
• Systematic data collection is expected to span 5–10 years, enabling comprehensive mapping of photo-reaction cross sections and branching ratios.
• Theoretical models including AMD, mean-field, large-scale shell model, and no-core shell model will be used to predict reactions, with uncertainties quantified via comparison to experiment.
• The integration of experimental data and model uncertainties into the TALYS reaction code will improve simulations of ultra-high-energy cosmic ray propagation in inter-galactic space.
• The project supports diverse applications, including medical isotope production, radiation safety, and understanding of lightning-induced nuclear reactions in the atmosphere.