Dawn of High Energy Spin Physics — In Memory of Michel Borghini

High energy spin physics with the polarized proton target in 1960s is shown. The dynamic polarization in which the electronic polarization is transferred to protons in paramagnetic material by means of magnetic coupling was proposed at the beginning of 1960s. The first N-N experiment using a polarized proton target was performed with the crystal of La[Formula: see text]Mg[Formula: see text] (NO[Formula: see text]24H[Formula: see text]O at CEN-Saclay and Berkeley in 1962, followed by [Formula: see text]-p experiments in several laboratories. Protons in organic materials were found to be polarized up to 80% in [Formula: see text]He cryostats in 1969. It was helpful for large background experiments. High proton polarization was interpreted in the spin temperature theory. Spin frozen targets were constructed in early 1970s and used for experiments which require wide access angle. Michel Borghini was a main player for almost all the above works.

Studies of Unstable Nuclei with Spin-Polarized Proton Target

Roles of spin-dependent interactions in unstable nuclei have been investigated via the direct reaction of radioactive ions with a solid spin-polarized proton target. The target has a unique advantage of a high polarization of 20–30% under low magnetic field of 0.1 T and at a high temperature of 100 K, which allow us to detect recoil protons with good angular resolution. Present status of on-going experimental studies at intermediate energies, such as proton elastic scattering and ([Formula: see text]) knockout reaction, and new physics opportunities expected with low-energy RI beams are overviewed.