Nuclear Theory Group

Members

Professors: K. Kubodera and F. Myhrer

Research Associate: A. Gardestig

Recent (2006) Ph.D.s: Ivan Danchev and Barbara Szczerbinska

Antimatter-matter annihilation

Today's particle accelerators enable us to create antimatter in the form of antiprotons, anti-electrons (positrons), etc. A prominent example is a very intense antiproton beam that was generated and stored at the Low Energy Antiproton Ring Facility at CERN in Geneva, Switzerland. Our group has been making an extensive theoretical study of mechanisms with which these antiprotons interact with protons (normal matter), and how matter and antimatter annihilate each other to produce elementary particles called the mesons. Our study helps to elucidate the fundamental building blocks of nature and the interactions governing them.

Solar neutrinos and neutrino oscillations.

The sun generates its energy through thermonuclear reactions. Some of these reactions emit particles called the neutrinos, which interact only very weakly with the environment and therefore can carry valuable information on how the sun burns its nuclear fuel. The 30-year old puzzlement, that the observed solar neutrino flux is significantly lower than expected from the standard solar model, has recently been resolved by careful analyses of the neutrino nuclear reactions in large water and heavy-water detectors, the SuperKamiokande detector in Japan and the heavy-water detector at the Sudbury Neutrino Observatory (SNO) in Canada. Detailed theoretical investigations of the interactions between the neutrinos and nuclei in the detectors are extremely important for planning experiments and also for analyzing data. Our group is a world leader in this research field. At present we are evaluating the radiative corrections to the neutrino deuteron reactions to enable the SNO research group to extract more precise values for the neutrino mixing parameters.

For recent calculations of neutrino cross sections relevant to SNO, see neutrino deuteron reactions.

Strangeness condensation in dense nuclear matter

The central part of a heavy atomic nucleus represents the highest matter density one would encounter under normal circumstances. In some astrophysical phenomena, however, matter can be compressed to much higher densities, and there is a possibility that these ultra-high dense systems contain as stable members strange particles, which, as the name suggests, do not feature as stable constituents in the ordinary environment. This phenomenon, called strangeness condensation, can play a very important role in a variety of astrophysical processes such as the cooling of neutron star, the remnant of a supernova explosion, the creation of mini blackholes, etc. Strangeness condensation is an extremely exciting topic in current nuclear physics, and our group is one of the front runners in this hotly pursued field. Our study is also connected to the large experimental project, RHIC (Relativistic Heavy Ion Collider). Many of the theoretical ideas we are proposing can be tested by experiments at RHIC, Brookhaven National Laboratory (New York).

Exchange currents in nuclei

It is commonly believed that atomic nuclei consist of protons and neutrons (jointly called the nucleons), and this picture is indeed capable of explaining many important nuclear phenomena. To be more accurate, however, we must consider the fact that the interactions among the nucleons are mediated by the exchange of mesons and that the presence of these mesons in nuclei give rise to observable effects, called the meson-exchange current (MEC) effects. Studying the MEC provides vital information on nuclear dynamics. Our group has been pioneering this study by formulating a reliable theoretical framework for describing MEC, and also by carrying out state-of-the-art numerical calculations the results of which show impressive agreement with the experimental data.

We have described above four of our main research areas at this moment. Needless to say, the frontiers of nuclear physics are constantly advancing, and we must, and we certainly will, keep our research interest as wide and flexible as possible to be abreast with the cutting edge of the field.