Measurement of the muon charge asymmetry from $W$ boson decays

We present a measurement of the muon charge asymmetry from $W$ boson decays using $0.3{\mathrm{fb}}^{-1}$ of data collected at $\sqrt{s}=1.96\mathrm{GeV}$ between 2002 and 2004 with the D0 detector at the Fermilab Tevatron $p\overline{p}$ Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.

Figure 1

(a) The combined trigger and reconstruction efficiency distributions by charge as a function of $\eta$ and (b) the ratio of these efficiencies fit to a constant, $0.99\pm 0.01$.

Figure 2

The isolation efficiency as a function of (a) $\eta$ (separated by muon charge) and (b) $p_T$ (for all muons) fit to a constant $0.921\pm 0.002$.

Figure 3

The muon charge asymmetry distribution. The horizontal bars show the statistical uncertainty and the full vertical lines show the total uncertainty on each point. The shaded (yellow) band is the envelope determined using the 40 CTEQ6.1M PDF uncertainty sets, the solid (red) line is the CTEQ6.1M central value, and the dotted (blue) line is the charge asymmetry determined using the MRST04 NLO PDFs. All three were determined using resbos and photos.

Figure 4

The folded muon charge asymmetry distribution. The horizontal bars show the statistical uncertainty and the full vertical lines show the total uncertainty on each point. The shaded (yellow) band is the envelope determined using the 40 CTEQ6.1M PDF uncertainty sets, the solid (red) line is the CTEQ6.1M central value, and the dotted (blue) line is the charge asymmetry determined using the MRST04 NLO PDFs. All three were determined using resbos and photos.