The Proton Spin

Fixed target experiment at CERN, SLAC and DESY have determined that the quark contribution to the spin of the proton and neutron accounts for approximately 1/3 of the total spin content of the nucleon. These studies performed in the 1990s are largely complete. The new Holy Grail in the field is to make a first definitive measurement of the gluon contribution to the proton spin.

Our group has recently joined the STAR collaboration at Brookhaven National Laboratory. The experiment will measure the gluon contribution to the proton spin by colliding spin-polarized protons at center of mass energies ranging from 200 GeV to 500 GeV. This endeavor is called the RHIC Spin program.