Nuclear Interactions Group (NIG)

The Nuclear Interactions Group (NIG) focuses on understanding the fundamental nature of nuclear interactions and the dynamical structure of nucleons and nuclei. The Nuclear Structure physics information is obtained by experiments in which high-energy beams of electrons or photons interact with target made of protons, few-body nuclear systems, or more complex nuclei. The scattered electrons and other particles ejected from the reaction are detected and the probabilities for such process to happen (cross sections) are extracted. Because the electrons and photons are point-like particles with no known internal structure or excited states, and because their electro-magnetic interaction with the target is relatively weak and well understood (as opposed to the strong interaction among the constituents of the target itself), they penetrate deeply into the target nucleon or nuclei without disturbing its substructure, thus enabling the extraction of the internal structure of the nuclear or nucleon target with a relatively easy interpretation.

The Nuclear Structurephysics information is obtained by experiments in which high-energy beams of electrons or photons interact with target made of protons, few-body nuclear systems, or more complex nuclei. The scattered electrons and other particles ejected from the reaction are detected and the probabilities for such process to happen (cross sections) are extracted. In many experiments, spin polarizations of the beam, target and/or the ejected particles are used to extract unique information. Because the electrons and photons are point-like particles with no known internal structure or excited states, and because their electro-magnetic interaction with the target is relatively weak and well understood (as opposed to the strong interaction among the constituents of the target itself), they penetrate deeply into the target nucleon or nuclei without disturbing its substructure, thus enabling the extraction of the internal structure of the nuclear or nucleon target with a relatively easy interpretation.

The Nuclear Interaction Group is also engaged in study of the electro-weak Standard Model. In particular, one can extract the weak coupling of quarks by measuring parity violation cross section difference of deep inelastic electron scattering on a isoscaler target.

To achieve the highest quality of the measurements, continuous-wave (CW) electron accelerators with energies of a few GeV are esential. The group, therefore, performs its experiments at facilites at the leading edge of the field, including MIT/Bates (Middleton, MA), the Thomas Jefferson National Accelerator Facility (JLab) (Newport News, VA), and MAMI (Mainz, Germany). You may choose " Previous Research ", "Research Highlights" and "Future Projects" to learn more about our completed, ongoing, as well as future research programs at these facilities.

At NIG, research is carried out at Bates, Mainz and JLab. NIG is a sponsor of many experiments at these facilities and the group provides a great deal of the leadership for the programs. Work includes substantial and novel facility development as part of a collaborative contribution. The major thrusts of our research program are:

(*) Structure of the Nucleon, Free and Bound: at Bates & JLab
The nucleon and its structure is simply another component of the strong interaction many-body problem and its study is integrated into the program as a free and as a bound nucleon. It must be understood from both points of view to extract with precision the currents in complex nuclei.

(*) The Two-Body Problem and It's Currents: at Bates & JLabThe two-body system is fundamental to an understanding of the interactions and currents needed in the structure of more complex systems. The progression through the three- and four-body systems is essential because these add growing complexity and can be calculated with the greatest precision.

(*) Testing Modern Models of Light Nuclei: at Bates, Mainz & JLab

(*) The Spin Structure of the Nucleon: at JLab
Study of the nucleon spin structure of the nucleon, espically the contribution from valence quarks, could reveil the source of nucleon spin, you can find an interesting story about it from our previous Ph.D. student.

(*) Multi-Nucleon Currents and Correlations in Nuclei. at Bates & JLab
The nucleon-nucleon short-range correlations are responsible for approximately 40% of the nuclear wave function and we know essentially nothing about these structures and the associated currents.