Confirmation of Yale Professor's Theory of Supersymmetry in Nuclei Advances Knowledge of Subatomic Physics

Supersymmetry in nuclei – the theory pioneered in 1980 by Yale Professor of Physics Francesco Iachello who predicted that every quantum state we see in some atomic nuclei has a super partner – is now a reality, thanks to the use of a new, high-power instrument used by scientists in Germany.

The existence of supersymmetry in the spectra of nuclei has major implications for other fields of physics, including particle physics, since it shows that supersymmetry can occur in Nature. The discovery validates Iachello’s prediction of the existence of bosons and their counterpart fermions in atomic nuclei.

To put it simply, supersymmetry, as described by Iachello, the Joshua W. Gibbs Professor of Physics at Yale, is an exotic type of symmetry that links together two types of particles, called bosons (particles with integer angular momentum) and fermions (particles with half-integer angular momentum).

In the August 23, 1999 issue of “Physical Review Letters,” Metz et al have reported direct experimental evidence for the occurrence of supersymmetry in the gold nucleus 196Au. The latest experiment, led by Jan Jolie (University of Fribourg, Switzerland) involving a major effort by several laboratories for several years, has been possible because of higher resolutions that can now be obtained with a new magnetic spectrometer developed by Gerhard Graw at the Tandem Accelerator of the Ludwig-Maximilians Universitat in Munich, Germany.

This research provided a spectrographic analysis that identified the bosonic and accompanying fermionic states in every instance – using a particle accelerator. Accelerators recreate, for a very short period of time, miniature versions of hot, primordial conditions to determine whether subatomic quantum states exist and whether they behave in the ways predicted by theory.

With the present resolutions available, it is now possible to separate individual quantum levels and thus conduct exact tests for the presence of all supersymmetric states.

Supersymmetry has been mostly sought in the field of particle physics, where it links the fundamental constituents, quarks and gluons, with hypothetical particles called squarks and gluinos, which have not yet been found.

In 1980, Iachello, the Joshua W. Gibbs Professor of Physics and a Professor of Chemistry, theorized that supersymmetry could also be observed in the spectra of heavy nuclei. The mathematical theory to describe supersymmetry in nuclei was co-authored by Itzhak Bars (a former associate professor at Yale and currently a professor at University of Southern California) and A. Baha Balantekin (a former Yale graduate student and now a professor at University of Wisconsin).

This suggestion was based on a model of atomic nuclei, called the Interacting Boson Model, and assumed that the supersymmetric partners were correlated pairs of protons and neutrons (bosons) and individual protons and neutrons (fermions).

Supersymmetry in nuclear physics is different from that in particle physics but shares the fundamental concept of invariance under a set of transformations linking bosons with fermions. Following Iachello’s suggestion in 1980, there were a number of frenzied experiments that suggested supersymmetry in nuclei, but they weren’t complete and didn’t show a match for every state found.

Professor Iachello received a Dott. Ing. Degree from the Politecnico di Torino, Italy, and a Ph.D. in theoretical physics from the Massachusetts Institute of Technology. He is the recipient of several honors, including the AKZO prize of the Dutch Academy of Sciences, the E.P. Wigner medal of the Group Theory and Fundamental Physics Foundation, the T. Bonner Prize of the American Physical Society, and Doctorates and Professorships from Universities in Europe and Asia. He is the originator of the interacting boson model of the nucleus, along with Professor A. Arima (Tokyo, Japan).