In an advance that merges the realms of theoretical physics and cutting-edge computing, researchers from the Oak Ridge National Laboratory (ORNL) have shed new light on the longstanding debate surrounding the magnetic dipole transition in calcium-48. Utilizing the formidable capabilities of Frontier, the world’s most powerful supercomputer, the team's findings, accounted for in a recent publication in Physical Review Letters, bring us closer to reconciling discrepancies between experiments that have, up until now, offered conflicting views on this nuclear behavior.
At issue is calcium-48's nucleus, an arrangement deemed "doubly magic" due to its full shells of protons and neutrons which yield exceptional stability, this particular isotope has been at the center of a dispute over its magnetic properties since the 1980s, when initial studies suggested a magnetic transition strength, measured at 4 nuclear magnetons squared, was called into question by a 2011 study which found the strength nearly double that, prompting ORNL physicists, led by Gaute Hagen, to employ state-of-the-art theoretical models and powerful computational techniques to probe into the issue further, "We’re very interested in the rules that govern how nuclei are made," Hagen told ORNL News.
Frontier's exascale capabilities allowed the ORNL team to use chiral effective field theory and the coupled-cluster method to accurately simulate the magnetic properties of calcium-48; their results lined up with the findings of the gamma ray study conducted in 2011. However, the team also discovered new facets of the nuclear interactions; they found that, contrary to past beliefs, nucleon-pair interactions within the nucleus during the magnetic transition could, in some instances, slightly increase the strength of the transition. Thomas Papenbrock, a physicist involved in the study, anticipates that "the computations will stimulate new discussions between the theorists and the experimentalists," hoping for a deepened collaboration, as mentioned by Oak Ridge National Laboratory.
According to ORNL News, the implications of these findings extend beyond the microcosmic. As ORNL's nuclear astrophysicist Raphael Hix explains, understanding calcium-48's magnetic transitions aids us in comprehending how neutrinos interact within supernovae, a key process in the cosmic cycle of star death and rebirth, shedding light on the assembly of elements throughout the universe. Bijaya Acharya, lead author of the study, reiterated the significance, noting, "The physics that describes the magnetic transition strength in calcium-48 also describes how neutrinos interact with matter." He explained that higher transition strengths could influence the dynamics of supernova explosions and, consequently, our understanding of stellar mechanics.
Supported by the DOE Office of Science and DOE’s SciDAC-5 NUCLEI Collaboration, the research at ORNL not only demonstrates an exemplary union of theoretical physics and computational science, but it also underlines the critical role of basic research in uncovering the fundamental forces of nature. With the next move now in the hands of experimental physicists, the scientific community watches with anticipation as each iteration of research slowly demystifies the inner workings of the atomic world.
