The (K−,π−) and (π+, K+) Reactions and Λ-Hypernuclear Polarization

Abstract

The theoretical studies of (K−, π−) and (π+, K+) reactions on p-shell targets are presented in the DWIA framework with use of the elementary spin-nonflip and spin-flip amplitudes. Calculations can explain the available experimental data of excitation functions and angular distributions of the (K−, π−) reactions at pK−=800 MeV/c and the (π+, K+) reactions at pπ+ = 1.04 GeV/c. Characteristic and distinguished features of the excitation functions and cross sections are exhibited. Especially it is demonstrated that the (K−, π−) reactions at pK−=1.1 GeV/c and 1.5 GeV/c can excite the unnatural parity states with comparable strength to the natural parity ones. Further interesting is that the (π+, K+) and (K−, π−) reactions with ∼1 GeV/c incident beams can be shown to produce very large polarizations of the produced hypernuclear states. Taking the subsequent deexcitation processes of the excited states into account, we have evaluated the hypernuclear polarization and Λ-spin polarization of the ground state and/or the ground-doublet states at the hypernuclear weak-decay stage, which would play a role in the hypernuclear coincidence experiment.