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 ⊥ 1T , which can provide an explanation on the transverse polarization of the Λ 0 hyperon produced in an unpolarized process. We calculate D ⊥ 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 Λ 1 to the DSV parametrization for D Λ 1 . In addition, we compute the longitudinal polarization fragmentation function G Λ 1 and compare it with the known parametrization of G Λ 1 . We also estimate the transverse polarizations of Λ production, in both semi-inclusive deep inelastic scattering and single inclusive e + e − annihilation.

Double Collins effect in e+e−→ΛΛ¯Wang1, Yang2, Lü3 2018Phys. Rev. DSelf Cite9030View full textAdd to dashboardCite

“…We note that similar violations of the positivity bound were also observed in Refs. [48,68,69]. An explanation was given in Ref.…”

“…Recently, the spectator model has also been extended to calculate the fragmentation function D ⊥ 1T of the Λ hyperon in Ref. [48]. In this case the spectator system is a diquark, and the calculation includes contributions from both the scalar diquark and vector diquark.…”

“…In Table I, we list the parameters [48] In Fig. 2, we plot the numerical result of H ðzÞ for the up and down quarks is around several percent.…”

“…[70], stating that the violation may arise from the fact that T-odd TMD distributions or fragmentation functions TABLE I. Values of the parameters used in the spectator diquark model [48]. The values of the last three parameters are fixed.…”

“…[20,57,62]. Following the previous work [48] in which the fragmentation function D ⊥ 1T for the Λ hyperon has been calculated in the same model, we perform the integration over the loop momentum l with the help of the Cutkosky cutting rules. In the left-hand side of Figs.…”