(Medium energy spin physics with lasers)

Abstract

During the first two years of this program, we have successfully investigated two new methods for the production of polarized muonic helium. This work was done at LAMPF in collarboration with a group from Syracuse University. Traditionally, polarized muonic helium has been formed by stopping polarized muons in unpolarized atoms. Unfortunately, because of depolarization in the muon cascade to the ground state, residual polarizations are only {approximately}3%. The two methods we have developed both achieve much higher muon polarizations. To accomplish our goals, we first developed an appropriate muon beam for use with our small gas targets. During the summer of 1990, we stopped unpolarized negative muons in nuclear polarized {sup 3}He. The muons were polarized in the cascade to the ground state through the hyperfine interaction with the nucleus. The resulting muon polarizations were 7.2 {plus minus} 0.8% for a 100% nuclear polarized target. While higher polarizations are clearly desirable for practical purposes, this experiment yielded important insights on spin interactions that occur in muonic atoms. Also, the ability to rapidly reverse the target polarization gave the experiment good sensitivity with minimal systematic effects. Last summer, we completed an experiment in which we polarized muonic helium by direct spinmore » interaction with an optically pumped Rb vapor. In this technique, the muonic helium atom is polarized through a combination of charge exchange and spin exchange with the polarized valence electron of the Rb vapor. In contrast to the technique described in appendix A, the {sup 3}He nuclei are not polarized. This last technique yielded dramatic polarizations approaching 50%.« less