Inclusive Hadron Production

Abstract

The initial stage of the investigation of single-spin asymmetry in inclusive hadron production was performed in the 1960s with the appearance of polarized proton beams with a kinetic energy of 400 MeV (March in Phys. Rev. 120:1874, 1960; Mcllwan et al. in Phys. Rev. 127:239, 1962) and 650 MeV (Borisov et al. in Sov. J. Nucl. Phys. 5:348, 1967). The first and second experiments were carried out with emulsions and bubble chambers, respectively; the third experiment was a purely electronic experiment (scintillation counters) with high statistics. In all these experiments, nonzero asymmetry of pions was observed. To interpret asymmetry in inclusive pion production at 650 MeV, the known Mandelstam isobar model (Mandelstam in Proc. R. Soc. A 244:491, 1958) was successfully used, whereas the one-pion exchange (OPE) model (Ferrari and Selleri in Nuovo Cimento 27:1450, 1963) appeared to be unsatisfactory (Nurushev and Solovyanov in Preprint No. R-2382, JINR, Dubna, Russia, 1965). These data were also useful for the phase shift analysis. Physicists made huge efforts to advance polarization investigations from energies about 100 MeV to energies ∼10⁵ GeV (in the laboratory frame) for 50 years. At the same time, the prevailing opinion is still that the spin phenomena insignificant and can disappear with increasing energy. However, already the first results from the RHIC collider showed that polarization effects survive even at energies of 10⁵ GeV. Now, it is possible to hope that polarization physics will bring many further surprising results. Single-spin asymmetries at high energies (>10 GeV) have been considered in several works where one can find particular results and details of discussions (Soffer in Proceedings of the workshop on the prospects of spin physics at HERA, Zeuthen, p. 370, 1995; Nurushev in Proceedings of the 2nd meeting held at Zeuthen, p. 3, 1995; Nurushev in Proceedings of the 2nd meeting held at Zeuthen, p. 75, 1995).