A study of polarized Λ production in deep inelastic postron scattering

Abstract

In the late 1980's, several experiments seemed to indicate that the spin of the proton did not come from the spin of the quarks. This was inconsistent with the view that the spin composition of baryons could be found using simple spin counting rules. Many advances, both theoretical and experimental, help explain other sources of nuclear spin, such as net orbital angular momentum or gluon spin. While some explanations may have been found for this spin crisis, it nonetheless sparked interest in spin phenomena in many other areas of particle and nuclear physics. For example, since the spin of the proton does not appear to come entirely from the spin of the quarks, what about other baryons? What generates their spin? If a polarized quark is generated in a high energy reaction and then hadronizes, how much of the polarization remains in the final state particles? Many measurements are necessary to answer these questions. As a first step, A particles are generated at the HERMES experiment in Hamburg, Germany, using a polarized positron beam and an unpolarized target. The polarization which is transferred to these final state A's depends not only on the spin composition of the A baryon, but also on the effects of polarization in the hadronization process. In this thesis, the results of the polarization transfer are reported and compared to possible theoretical models.