The Gluon Sivers Distribution in D Production at Rhic

The single transverse spin asymmetry in D meson production at RHIC can provide a clean measure of the gluon Sivers distribution function. At intermediate rapidity, D production is largely dominated by the elementary gg -> cbar c channel, where there cannot be any transverse spin transfer. Therefore, any transverse single spin asymmetry observed for D's produced in p^↑p interactions can only originate from the Sivers effect in the gluon distribution functions. A sizeable transverse single spin asymmetry measured by PHENIX or STAR experiments would then give direct information on the size of the gluon Sivers distribution function.