Number 133 (Story #4), June 17, 1993 by Phillip F. Schewe and Ben Stein WHERE DOES THE NEUTRON GET ITS SPIN? Two experiments address this issue. At CERN the Spin Muon Collaboration (SMC) scatters polarized muons from a target of polarized deuterons, while at Stanford the E142 collaboration scatters polarized electrons from a target of polarized helium-3 atoms. In both cases the study of deep inelastic scattering events---inelastic because some of the collision energy is converted into extra particles and "deep" because the lepton probes the neutron at a very small distance scale---allows scientists to determine how much of the neutron's spin can be ascribed to its constituent quarks. The CERN result, 6% (with an uncertainty of 25%), is quite different from the Stanford result, 57% (with an uncertainty of 11%). New experiments at both labs may resolve the issue. (Nature, 13 May 1993.)