The systematic uncertainty and measurement approach of the sea quark Sivers Function of the Fermilab SpinQuest experiment.*

More than three decades after the initial spin crisis there is still much uncertainty concerning the internal dynamics of the partons inside the nucleon. As an essential step in solving the crisis, Fermilab’s SpinQuest experiment (E1039) will for the first time measure the sign, magnitude and shape of the sea quark Sivers function with sub-percent precision. The experiment will take advantage of Fermilabs’s 120 GeV proton beam at the greatest instantaneous proton intensity ever on a dynamically vertically polarized solid target. The prospects of the measurement and the projected uncertainties of the SpinQuest experiment will be discussed.