Transverse Quark Spin Effects and the Flavor Dependence of the Boer-Mulders Function

Understand

The naive time reversal odd (``T-odd'') parton distribution $h_{1}^{\perp}$, the so-called Boer-Mulders function, for both up ($u$) and down ($d$) quarks is considered in the diquark spectator model.

• While the results of different articles in the literature suggest that the signs of the Boer-Mulders function in semi-inclusive DIS for both flavors $u$ and $d$ are the same and negative, a previous calculation in the diquark-spectator model found that $h_{1}^{\perp(u)}$ and $h_{1}^{\perp(d)}$ have different signs.
• The flavor dependence is of significance for the analysis of the azimuthal $\cos(2\phi)$ asymmetries in unpolarized SIDIS and DY-processes, as well as for the overall physical understanding of the distribution of transversely polarized quarks in unpolarized nucleons.
• We find substantial differences with previous work.