Experiments with Polarized ³He and Muonic ³He: Pion Elastic Scattering and Muon Capture

Abstract

Novel asymmetry measurements on the A=3 system using secondary beams of pions and muons have recently become feasible. Asymmetries A _y for π ⁺ elastic scattering have been measured for the first time across the P ₃₃ resonance region. The asymmetries are large and change sign between 180 and 256 MeV. The data disagree in detail with calculations that use Faddeev wavefunctions for ³He and first-order optical potentials. Inclusion of a Δ-neutron spin-spin interaction greatly improves the agreement with the data.

Muonic ³He has been polarized on the time scale of the muon lifetime by direct spin exchange with optically pumped Rb vapor. Asymmetries for 1.9 MeV tritons from muon capture have been observed for the first time. With future improvements of the experiment the vector analyzing power for the tritons may provide an accurate and nearly model independent value for the induced pseudoscalar coupling g p of the weak interaction.

For the E1267 Collaboration: S.P. Blanchard, E.J. Brash, B. Brinkmöller, G.R. Burleson, W.J. Cummings, B.J. Davis, D. Dehnhard, P.P.J. Delheij, C.M. Edwards, M.A. Espy, R. Henderson, B.K. Jennings, M.K. Jones, B.A. Lail, J.L. Langenbrunner, B. Larson, W. Lorenzon, K. Maeda, C.L. Morris, B. Nelson, J.M. O’Donnell, M.A. Palarczyk, B.K. Park, S.I. Penttilä, D.R. Swenson, D. Thiessen, D. Tupa, Q. Zhao.

For the E683 Collaboration: J. Behr, P. Bogorad, E.J. Brash, G.D. Cates, W.J. Cummings, A. Gorelov, M D Hasinoff, R. Henderson, K. Hicks, R. Holmes, J.C. Huang, K. Kumar, B. Larson, W. Lorenzon, G.M. Marshall, J McCracken, E. Saettler, P.A. Souder, D. Swenson, D. Tupa, X. Wang, A. Young.