Model calculations of the Sivers function satisfying the Burkardt Sum Rule

Abstract

It is shown that, at variance with previous analyses, the MIT bag model can explain the available data of the Sivers function and satisfies the Burkardt Sum Rule to a few percent accuracy. The agreement is similar to the one recently found in the constituent quark model. Therefore, these two model calculations of the Sivers function are in agreement with the present experimental and theoretical wisdom.

Figures (4)

• Figure 1: The contributions to the Sivers function in the present approach. The graph has been drawn using JaxoDraw Binosi:2003yf.
• Figure 2: The quantity $f_{1T}^{\perp (1)q }(x)$, Eq. (\ref{['momf']}), for the $u$ and $d$ flavour. The dashed curves are the results of the approach of Ref. yuan, the full ones those obtained here.
• Figure 3: The same as in Fig. 2, after NLO evolution (see text). The patterned area represents the $1 - \sigma$ range of the best fit of the HERMES data proposed in Ref. coll3.
• Figure 4: The same as in Fig. 3, but comparing with the parameterization of the data proposed in Ref. ans (patterned area).