Polarization in hadronic Λ hyperon production and chiral-odd twist-3 distribution

Polarization of the \ensuremath{\Lambda} hyperon produced with a large transverse momentum in unpolarized nucleon-nucleon collisions 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 \ensuremath{\Lambda}. Our simple model estimate for this contribution indicates that it gives rise to a significant \ensuremath{\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 pion production at ${x}_{F}\ensuremath{\rightarrow}1.$