Effect of asymmetric strange seas and isospin-violating parton distribution functions on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">sin</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>θ</mml:mi></mml:mrow><mml:mrow><mml:mi>W</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>measured in the NuTeV experiment

The NuTeV Collaboration recently reported a value of ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{W}$ 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, $s(x)=\overline{s}(x),$ and (2) up and down quark distributions are symmetric under the simultaneous interchange of $u\ensuremath{\leftrightarrow}d$ and $p\ensuremath{\leftrightarrow}n.$ We report the impact of violations of these symmetries on ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{W}$ and discuss the theoretical and experimental constraints on such asymmetries.