Are all Boer-Mulders functions alike?

Chirally odd generalized parton distributions (GPDs) and the Boer-Mulders function provide valuable information about spin-orbit correlations for quarks in nucleons and other hadrons. We compare results for the relevant GPD ${\bar{E}}_T^q$ from a variety of phenomenological models as well as recent lattice results. We find that ${\bar{E}}_T^q>0$ for nucleons as well as the pion and for both $u$ and $d$ quark. As a result, the corresponding Boer Mulders functions are all expected to be negative. The sign of ${\bar{E}}_T^q$ arises from the relative sign between the upper and lower Dirac components for the quark wave functions.