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

Leonard P. Gamberg; Gary R. Goldstein; Marc Schlegel

Paper

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

Abstract

The naive time reversal odd (``T-odd'') parton distribution

, the so-called Boer-Mulders function, for both up (

) and down (

) 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

and

are the same and negative, a previous calculation in the diquark-spectator model found that

and

have different signs. The flavor dependence is of significance for the analysis of the azimuthal

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. In particular we obtain half and first moments of Boer-Mulders function that are negative over the full range in Bjorken

for both the

- and

- quarks. In conjunction with the Collins function we then predict the

azimuthal asymmetry for

and

in this framework. We also find that the Sivers

- and

- quark are negative and positive respectively. As a by-product of the formalism, we calculate the chiral-odd but ``T-even'' function

, which allows us to present a prediction for the single spin asymmetry

for a longitudinally polarized target in SIDIS.