Measurement of the Electron Charge Asymmetry in Inclusive $W$ Production in $pp$ Collisions at $\sqrt{s}=7\mathrm{TeV}$

A measurement of the electron charge asymmetry in inclusive $pp\to W+X\to e\nu +X$ production at $\sqrt{s}=7\mathrm{TeV}$ is presented based on data recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of $840{\mathrm{pb}}^{-1}$. The electron charge asymmetry reflects the unequal production of $W^{+}$ and $W^{-}$ bosons in $pp$ collisions. The electron charge asymmetry is measured in bins of the absolute value of electron pseudorapidity in the range of $|\eta |<2.4$. The asymmetry rises from about 0.1 to 0.2 as a function of the pseudorapidity and is measured with a relative precision better than 7%. This measurement provides new stringent constraints for parton distribution functions.

Figure 1

Signal plus background fit to data ${\mathrm{E̸}}_T$ distributions for positrons (left) and electrons (right) in data. Results are shown for the first pseudorapidity bin ($|\eta |<0.2$, top) and for the tenth pseudorapidity bin ($2.0<|\eta |<2.2$, bottom). The hatched area represents the statistical and systematic uncertainties associated with the fitting procedure.

Figure 2

Comparison of the measured electron asymmetry to the predictions of different PDF models for the electron $p_T>35\mathrm{GeV}$. The error bars include both statistical and systematic uncertainties. The data points are placed in the center of the $|\eta |$ bins. The PDF uncertainty bands are estimated using the PDF reweighting technique and correspond to a 68% confidence level.