Structure and Production of Lambda Baryons

Abstract

We discuss the quark parton structure of the $Λ$ baryon and the fragmentation of quarks into $Λ$ baryons. We show that the hyperfine interaction, responsible for the $Δ$-$N$ and $Σ^0$-$Λ$ mass splittings, leads not only to sizeable SU(3) and SU(6) symmetry breaking in the quark distributions of the $Λ$, but also to significant polarized non-strange quark distributions. The same arguments suggest flavor asymmetric quark fragmentation functions and non-zero polarized non-strange quark fragmentation functions. The calculated fragmentation functions give a good description of all measured observables. We predict significant positive $Λ$ polarization in semi-inclusive DIS experiments while models based on SU(3) flavor symmetry predict zero or negative $Λ$ polarization. Our approach also provides a natural explanation for the dependence of the maximum of the $ξ=\ln(1/z)$ spectrum on the mass of the particles produced in $e^+e^-$ annihilation.