Transverse polarization of the $Λ$ hyperon from unpolarized quark fragmentation in the diquark model

Abstract: We investigate the spin-dependent (naive) T-odd fragmentation function $D^\perp_{1T}$, which can provide an explanation on the transverse polarization of the $\Lambda^0$ hyperon produced in an unpolarized process. We calculate $D^\perp_{1T}$ for light flavors in the spectator diquark model, with a Gaussian form factor at the hyperon-quark-diquark vertex. We include in the calculation both the scalar diquark and axial-vector diquark spectators. We determine the values of the model parameters by fitting the unpolarized fragmentation function $D^\Lambda_1$ to the DSV parametrization for $D^\Lambda_1$. In addition, we compute the longitudinal polarization fragmentation function $G^\Lambda_1$ and compare it with the known parametrization of $G^\Lambda_1$. We also estimate the transverse polarizations of $\Lambda$ production, in both semi-inclusive deep inelastic scattering and single inclusive $e^+e^-$ annihilation.