Impact parameter dependent parton distributions and transverse single spin asymmetries

Generalized parton distributions (GPDs) with a purely transverse momentum transfer can be interpreted as Fourier transforms of the distribution of partons in impact parameter space. The helicity-flip GPD E(x,0,-Delta(perpendicular to)(2)) is related to the distortion of parton distribution functions in impact parameter space if the target is not a helicity eigenstate, but has some transverse polarization. This transverse distortion can be used to develop an intuitive explanation for various transverse single spin asymmetries.