Reduction of the electroweak correlation in the PDF updating by using the forward-backward asymmetry of Drell-Yan process

We propose a new observable for the measurement of the forward-backward asymmetry (A(FB)) in Drell-Yan lepton production. At hadron colliders, the AFB distribution is sensitive to both the electroweak (EW) fundamental parameter sin(2)theta(W), the weak mixing angle, and the parton distribution functions (PDFs). Hence, the determination of sin2 theta(W) and the updating of PDFs by directly using the same A(FB) spectrum are strongly correlated. This correlation would introduce large bias or uncertainty into both precise measurements of EW and PDF sectors. In this article, we show that the sensitivity of AFB on sin2 theta(W) is dominated by its average value around the Z pole region, while the shape (or gradient) of the AFB spectrum is insensitive to sin2 theta(W) and contains important information on the PDF modeling. Accordingly, a new observable related to the gradient of the spectrum is introduced, and demonstrated to be able to significantly reduce the potential bias on the determination of sin2 theta(W) when updating the PDFs using the same AFB data.

Automated summary

This article proposes a new observable for measuring the forward-backward asymmetry in Drell-Yan lepton production. The new observable can reduce potential biases in determining the electroweak fundamental parameter sin2 theta(W) when updating parton distribution functions using the same measurement data.