Polarization in Hadronic \Lambda Hyperon Production and Chiral-Odd Twist-3 Distribution

Abstract

Polarization of the \Lambda hyperon produced with a large transverse momentum in the unpolarized nucleon-nucleon collision is analyzed in the framework of QCD factorization. We focus on the mechanism in which the soft-gluon component of the chiral-odd spin-independent twist-3 quark distribution E_F(x,x) becomes a source of the polarized quark fragmenting into the polarized \Lambda. Our simple model estimate for this contribution indicates that it gives rise to a significant \Lambda polarization at large x_F. This is in parallel with the observation that the soft gluon pole mechanism gives rise to a large single transverse spin asymmetry in the pion production at x_F\to 1.