Sivers Function in the MIT Bag Model

Abstract

The Sivers function, an asymmetric transverse-momentum distribution of the quarks in a transversely polarized nucleon, is calculated in the MIT bag model. The bag quark wave functions contain both $S$-wave and $P$-wave components, and their interference leads to nonvanishing Sivers function in the presence of the final state interactions. We approximate these interactions through one-gluon exchange. An estimate of another transverse momentum dependent distribution $h_1^\perp$ is also performed in the same model.

Figures (5)

• Figure 1: The leading contribution to the Sivers function $f_{1T}(x,k_\perp)$ in the MIT bag model.
• Figure 2: The Sivers functions $f_{1T}^\perp(x,k_\perp)$ for the valence quarks at $x=0.3$ as functions of $k_\perp$, where the quark-gluon coupling $\alpha_s=0.2$.
• Figure 3: The bag model prediction for the asymmetry of the quark distribution in a transverse polarized proton as a function of $k^x$ and $x$, where $\alpha_s=0.2$.
• Figure 4: The first moments of the Sivers functions $f_{1T}^{(1)}(x)$ for valence quarks, where $\alpha_s=0.2$.
• Figure 5: $h_{1}^\perp(x,k_\perp)$ for the valence quarks at $x=0.3$ as functions of $k_\perp$, where $\alpha_s=0.2$.