Strongly Resonating Bosons in Hot Nuclei

TL;DR

This paper investigates resonant interactions of alpha particles in hot nuclei formed during heavy-ion collisions, revealing multiple resonance states including the Hoyle state and possible Efimov states, through experimental analysis.

Contribution

It provides new experimental evidence of multiple alpha resonance states, including the Hoyle and Efimov states, in hot nuclear environments created by heavy-ion collisions.

Findings

Observation of 8Be resonance levels at specific energies.

Identification of excited states of 12C, including the Hoyle state.

Detection of potential Efimov state in 3-alpha system.

Abstract

When two heavy ions near the Fermi energy collide, a warm and low-density region can form in which fragments appear. This region is mainly dominated by proton (p) and alpha particles. In such an environment, the alphas interact with each other, and especially through strong resonances, form complex systems such as 8Be and 12C. Our experiments show that in the reactions 70(64)Zn(64Ni)+70(64)Zn(64Ni) at E/A=35 MeV/nucleon levels of 8Be appear around relative energies Eij=0.092 MeV, 3.03 MeV as well as above 10 MeV and 100 MeV. For the 3 alpha systems, multi resonance processes give rise to excited levels of 12C. In particular, the Hoyle state at 7.654 MeV excitation energy shows a decay component through the ground state of 8Be and also shows components where two different alpha couples are at relative energies consistent with the ground state of 8Be at the same time. A component where the three alpha relative energies are consistent with the ground state of 8Be (i.e., E12=E13=E23=0.092 MeV) is also observed at the 7.458 MeV excitation energy, which was suggested as an Efimov state.