Measurement of the Effective Weak Mixing Angle in $p\bar{p}\to Z/{\gamma }^{\ast }\to {\ell }^{+}{\ell }^{-}$ Events

Abstract

We present a measurement of the effective weak mixing angle parameter ${\sin }^2{\theta }_{\text{eff}}^{\ell }$, in $p\bar{p}\to Z/{\gamma }^{\ast }\to {\mu }^{+}{\mu }^{-}$ events at a center of mass energy of 1.96 TeV, collected by the D0 detector at the Fermilab Tevatron Collider and corresponding to 8.6 fb${}^{-1}$ of integrated luminosity. The measured value of ${\sin }^2{\theta }_{\text{eff}}^{\ell }[\mu \mu ]=0.23016\pm 0.00064$ is further combined with the result from the D0 measurement in $p\bar{p}\to Z/{\gamma }^{\ast }\to e^{+}{e}^{-}$ events, resulting in ${\sin }^2{\theta }_{\text{eff}}^{\ell }[\text{comb.}]=0.23095\pm 0.00040$. This combined result is the most precise measurement from a single experiment at a hadron collider and is the most precise determination using the coupling of the $Z/{\gamma }^{\ast }$ to light quarks.

submitted to Phys. Rev. Lett