Transverse Lambda polarization in semi-inclusive DIS

Abstract

Following a previous description of Lambda and Lambda-bar polarization in unpolarized p-p interactions, within a perturbative QCD factorization scheme with new polarizing fragmentation functions, here we investigate the transverse polarization of Lambda's and Lambda-bar's produced in semi-inclusive DIS. Analytical expressions for both neutral and charged current exchange are given. Since quantitative predictions cannot be given at this stage and comparison with existing data are not yet significant, we present the general formalism and a qualitative analysis displaying generic features of the Lambda and Lambda-bar polarization for specific scenarios. Different kinematical situations are considered, corresponding to experiments currently able to study Lambda production in semi-inclusive DIS.

Figures (3)

• Figure 1: Kinematical representation of the semi-inclusive hadron production process, as viewed in the virtual boson-target proton c.m. reference frame (VN frame). The $\hat{z}$ axis is taken along the virtual boson direction of motion; the $\hat{x}$ axis is along the direction of the hadron transverse momentum, $\hbox{\boldmath$p$}_{_T}\equiv \hbox{\boldmath$k$}_\perp$; the $\hat{y}$ axis is chosen to form a right-handed frame. The direction of positive transverse (with respect to the production plane) polarization $\hbox{\boldmath $P$}_{_T}$, in the four quadrants, is shown explicitly by the arrows.
• Figure 2: Transverse $\Lambda$ polarization, $P_{_T}^{\Lambda}$, vs.$z_h$ and averaged over $p_{_T}$, for several SIDIS production processes, with scenario 1 (on the left) and scenario 2 (on the right) for the polarizing FF (see text for more details).
• Figure 3: Transverse $\bar{\Lambda}$ polarization, $P_{_T}^{\bar{\Lambda}}$, vs.$z_h$ and averaged over $p_{_T}$, for several SIDIS production processes, with scenario 1 (on the left) and scenario 2 (on the right) for the polarizing FF (see text for more details).