A measurement of the muon charge asymmetry in W boson events

TL;DR

This paper reports a measurement of muon charge asymmetry in W boson decays using D0 detector data, revealing discrepancies with theoretical predictions in certain kinematic regions, which can refine parton distribution functions.

Contribution

It provides the first detailed measurement of muon charge asymmetry in W events across different muon transverse momentum bins, highlighting areas where theory and experiment diverge.

Findings

Reasonable agreement for inclusive muon transverse momentum

Discrepancies in asymmetry data at specific ta bins and ta-ta bins

Data more precise than current NLO QCD predictions

Abstract

A recent measurement by the D0 Collaboration, of the charge asymmetry of muons in $W\rightarrow\mu\nu$ events is discussed. Using 4.9 fb$^{-1}$ of data collected by the D0 detector, the muon charge asymmetry, $A(\eta)$, where $\eta$ is the muon pseudorapidity, is measured inclusively and in two bins of muon transverse momentum, \ptmu. After being corrected for background contamination and detector effects (resolution and acceptance), the data are compared to NLO QCD predictions with CTEQ 6.6 PDFs. For inclusive \ptmu, reasonable agreement is observed. However, the prediction fails to describe the data in bins of \ptmu. In most $\eta$ bins, the data are more precise than the predictions, and will provide tight constraints on future PDFs.