Spin content of Lambda and its longitudinal polarization in e+e−e^+e^- annihilation at high energies

Longitudinal polarization of Lambda produced in $e^+e^-$ annihilation at LEP energies is calculated in a picture for the spin content of Lambda which is consistent with the polarized deep inelastic lepton-nucleon scattering data and SU(3) flavor symmetry for hyperon decay so that the spin of Lambda is not completely carried by its $s$-valence quark. A comparison with the recent ALEPH data and the results of earlier calculations based on the static quark model in which the spin of Lambda is completely determined by the $s$-quark is given. The result shows that further measurements of such polarization should provide useful information to the question of which picture is more suitable in describing the spin effects in the fragmentation processes.Comment: 12 pages, 2 figure

Single spin asymmetries in inclusive high energy hadron-hadron collision processes

It has been realized for quite a long time that single-spin experiments, in which one of the colliding objects is transversely polarized, can be helpful in studying the properties of strong interaction in general and in testing Quantum Chromodynamics (QCD) in particular. Striking effects have been observed in the past few years which deviate drastically from the expectation of the perturbative QCD parton model. These effects have received much attention. New experiments of the similar type are underway and/or planned. Different theoretical attempts have been made to understand these effects. In this review, the special role played by singly polarized high-energy hadron-hadron collisions in High Energy Spin Physics is emphasized. Characteristics of the available data for inclusive hadron productions are briefly summarized. Different theoretical approaches for such processes are reviewed with special attention to a non-perturbative model which explicitly takes the orbital motion of the valence quarks and hadronic surface effects into account. The connection between such asymmetries and hyperon polarization in unpolarized reactions is discussed. An example of the possible application of such experimental results in other processes is given.Comment: 62 pages, 17 ps-figures (Review article to appear in Inter. J. Mod. Phys. A

Spin-polarized states of nuclear matter

The equations of state of spin-polarized nuclear matter and pure neutron matter are studied in the framework of the Brueckner-Hartree-Fock theory including a three-body force. The energy per nucleon $E_A(\delta)$ calculated in the full range of spin polarization ${\delta} = \frac{\rho_{\uparrow}-\rho_{\downarrow}}{\rho}$ for symmetric nuclear matter and pure neutron matter fulfills a parabolic law. In both cases the spin-symmetry energy is calculated as a function of the baryonic density along with the related quantities such as the magnetic susceptibility and the Landau parameter $G_0$. The main effect of the three-body force is to strongly reduce the degenerate Fermi gas magnetic susceptibility even more than the value with only two body force. The EOS is monotonically increasing with the density for all spin-aligned configurations studied here so that no any signature is found for a spontaneous transition to a ferromagnetic state.Comment: Contribution to GISELDA Meeting, 14-18 January, 2002 (Frascati), to appear in World Scientific (Singapore