Using Drell-Yan forward-backward asymmetry to constrain parton distribution functions

We show that measurements of the forward-backward charge asymmetry ($A_{FB}(M,y)$) of Drell-Yan dilepton events produced at hadron colliders provide a new powerful tool to constrain Parton Distribution Functions (PDFs). PDF uncertainties are the dominant source of systematic error in precision measurements at hadron colliders (e.g. $\sin^2\theta_{eff}(M_Z)$, $\sin^2\theta_{W}=1-M_W^2/M_Z^2$ and the mass of the W boson). We show that the $\chi^2$ values of fits to extract $\sin^2\theta_{eff}^{lept}(M_Z)$ from $A_{FB}(M,y)$ with different PDF replicas can be used to place additional constraints on PDFs. In turn, using these constrained PDFs significantly reduces the PDF errors in precision measurements of electroweak parameters.