Experimental Nuclear Physics and Fundamental Interactions at Indiana University

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The experimental nuclear physics group at Indiana University-Bloomington measures the properties of sub-atomic particles and systems with a special emphasis on the breaking of symmetries that might lead to new forces and effects. This work is organized around the following four questions:What is the origin of the spin of the proton? Experiments show that, contrary to expectation, the quark spins carry a small fraction of the total. Gluons, the carriers of the strong force, and the orbital motion of quarks inside the proton are the only other possibilities. We use high-energy polarized proton-proton collisions at the Brookhaven National Laboratory to measure the gluon contribution to the proton spin and also search for information on the quark's orbital motion.Why is more matter than antimatter left over after the end of the Big Bang? Matter and antimatter in the expansion of the universe are created and annihilated in equal amounts unless processes exist which depend on the direction of time. Time reversal violation also gives rise to the spontaneous separation of positive and negative electric charge along the spin axis of fundamental particles. Searches for such a separation are underway using an electric field to induce a bulk matter magnetization in a garnet crystal and to precess the spin axis of neutrons captured in a liquid helium bath.What are the properties and interactions of neutrinos? These elusive particles formed during nuclear and particle decay can change in flight from one type to another. New data at low energies from the MiniBooNE detector at Fermilab seem to indicate that such changes do not fit into the standard pattern established by the number of known quarks and leptons. Work to compare neutrino and anti-neutrino effects and measure neutrino-induced reactions is underway. We will also check to see if neutrinos are their own anti-particles.How strong are the parts of the weak force? This force causes nuclear beta decay and other nuclear reactions that violate mirror symmetry. Experiments are in preparation to search for mirror-asymmetry in the photons from neutron-proton capture and for a corkscrew motion of neutron spins as they travel through liquid helium. We also propose to measure the lifetime and decay properties of the neutron itself.We share the knowledge gained by this work and our experiences in scientific research through Open Houses, laboratory tours, science café discussions, and news items in the local public media. We strive to awaken the interest of students in the local school system in science by visiting science classes, conducting career presentations, judging science fair projects, participating in events at the Science Olympiad, and performing physics demonstrations at the Indiana State Fair. We prepare the next generation of scientists, educators, and technically-trained people for industry by educating post-doctoral research assistants, graduate students, undergraduates, and high school students. We organize summer schools for nuclear physics and its various specialties. With the resources available at a laboratory with its own suite of accelerators, we also provide new detectors and experimental technologies that expand the research possibilities across the nation in ways that are beyond the reach of many university departments. We share this technology base with a proton beam cancer treatment facility at the IU Health Proton Therapy Center, which has treated more than 1000 patients with a staff composed in part of our former students and postdocs.