The Fractional Down Quark Polarization in the Nucleon

Dr. Tony Forest
Department of Physics
Idaho State University


ISU's intermediate energy nuclear physics group is presently involved in several fundamental physics measurements. This talk will describe a program to measure the fractional polarization of down quarks in a nucleon using polarized electrons to probe polarized nucleon targets. Quantum chromodynamcs (QCD) is a theory of the strong interaction; one of the four fundamental forces in nature. QCD predicts that the down quark will carry all of the nucleon's spin and result in a fractional polarization of unity when the probe interacts with down quarks that crry all of the nucleon's momentum. This theory contradicts the leading constituent quark model of the nucleon. The world's current data set is unable to discriminate between QCD's prediction above and the constituent quark model. A description of this experimental program and the roles of ISU graduate students will be described.