Effect of asymmetric strange seas and isospin-violating parton distribution functions onsin2θWmeasured in the NuTeV experiment

The NuTeV Collaboration recently reported a value of ${\sin }^2{\theta }_W$ measured in neutrino-nucleon scattering that is 3 standard deviations above the standard model prediction. This result is derived assuming that (1) the strange sea is quark-antiquark symmetric, $s\left(x\right)=\overline{s}\mathrm{}\left(x\right),$ and (2) up and down quark distributions are symmetric under the simultaneous interchange of $u\leftrightarrow d$ and $p\leftrightarrow n.\mathrm{}$ We report the impact of violations of these symmetries on ${\sin }^2{\theta }_W$ and discuss the theoretical and experimental constraints on such asymmetries.