Studies in Experimental Nuclear Physics at Indiana University

Indiana University, Bloomington IN

Investigators

Abstract

The Indiana nuclear physics group plans to assume a leading role in the investigation of the following critical questions in nuclear physics. The spin of the proton is an essential property that determines the structure of matter, yet we know that only a small part of the spin comes from the three quarks that form the proton. The STAR-SPIN group would definitively measure the contribution from the gluons, the short-lived particles that hold the quarks together and which account for much of its mass to see if that is where the missing spin resides.The measurement of the gluon contribution to the proton spin will be carried out by adding a special detector for high energy gamma rays to the STAR detector located at the Relativistic Heavy Ion Collider. The detector is now being built using separate NSF construction funds. The force between pairs of neutrons and protons cannot, by itself, account for the strength that binds the nucleus together. New, three-body forces are needed, but their form is almost unknown. By manipulating the neutron and proton spins when three of them come together, the PINTEX collaboration would produce a map to guide a theory of such three-body force. . FY2002 will be the last year of data taking using the intense beams and unique capabilities of the Indiana University Cooler Facility to study these three-body forces. The weak force between nucleons, which can change the form of matter, is still poorly understood. By making a measurement accurate to one part in a billion on the formation of a deuteron from a neutron and a proton, the IU neutron group would measure the longest-range part of the weak force . The Indiana group would support studies of the weak force and other effects accessible using cold neutrons at NIST and LANSCE and by providing crucial parts of the experimental apparatus. There is mounting evidence that neutrinos, one of the most ubiquitous particles in the universe, may have mass, thus changing our most elegant theories of matter and how it controls the expansion of the universe. The neutrino group would check a recent observation from LANL of a few cases where neutrinos, because they have mass, spontaneously change from one neutrino type into another by collecting a large enough data sample to settle this issue. A key component of the Indiana program will be the training of students to become the next generation of researchers. This effort includes the involvement of post-doctoral associates in critical experimental roles, guiding the research of graduate students, involving undergraduates through the NSF-funded REU summer program and part-time employment, and reaching out to make the community aware of our scientific mission.