Transverse Quark Spin Effects and the Flavor Dependence of the Boer-Mulders Function
The naive time reversal odd (T-odd) parton distribution $$h_{1}^{\perp}$$, the so-called Boer-Mulders function, for both $$u$$- and $$d$$-quarks is considered in the diquark spectator model. While other approaches give evidence that the signs of the Boer-Mulders function for both flavors $$u$$ and $$d$$ are the same and negative, previous caculations in the diquark-spectator model found $$h_{1}^{\perp(u)}$$ and $$h_{1}^{\perp(d)}$$ have differnet 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. In particular we obtain estimates of the zeroth, half and first moments of Boer-Mulders functions that are negative over the full range in Bjorken $$x$$ for both the up and down quarks. In conjunction with the Collins function we then predict the $$\cos(2\phi)$$ azimuthal asymmetry for $$\pi^{+}$$ and $$\pi^{-}$$ in this framework. We also find that the Sivers up and down quark are negative and postive respectively. As a by-product of the formalism, we calculate the chiral-odd but T-even function $$h_{1L}^{\perp}$$ in the spectator framework, which allows us to present a prediction for the single spin asymmetry $$A_{UL}^{\sin(2\phi)}$$ for a longitudinally polarized target in SIDIS.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 910299
- Report Number(s):
- JLAB-THY-07-690; DOE/OR/23177-0094; TRN: US0704153
- Country of Publication:
- United States
- Language:
- English
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