Conventional Physics Explanations for the NuTeV sin2ThetaW

TL;DR

The paper rigorously tests whether conventional physics can explain NuTeV’s anomalously high value of $\sin^2\theta_W$ by evaluating EW radiative corrections, QCD effects, PDFs (including isospin and strange asymmetries), charm production, and nuclear corrections. It finds that higher-order QCD corrections are small and perturbatively stable, and that experimental cuts do not inflate the corrections; strange-antistrange asymmetry would tend to worsen the discrepancy, and sizable isospin violation would be required beyond plausible expectations. Overall, the standard-model explanations examined do not reconcile the NuTeV result, suggesting either a subtle combination of effects or a need for new physics or more precise global analyses. The work highlights the importance of cross-checks, alternative radiative-correction calculations, and refined parton distributions in resolving the tension between NuTeV and SM predictions.

Abstract

The NuTeV experiment has measured sin^2Theta_W = 0.2277 +/- 0.0013(stat) +/- 0.0009(syst), approximately 3 standard deviations above the standard model prediction. This discrepancy has motivated speculation that the NuTeV result may be affected significantly by neglected experimental or theoretical effects. We examine the case for a number of proposed explanations.

Figures (7)

• Figure 1: The measurements of $\hbox{$R_{\rm exp}^{\nu}$}$ and $\hbox{$R_{\rm exp}^{\overline{\nu}}$}$, shown as an error ellipse. The uncertainties in the error ellipse include theoretical uncertainties in relating $\hbox{$R_{\rm exp}^{\nu}$}$ and $\hbox{$R_{\rm exp}^{\overline{\nu}}$}$ to fundamental electroweak parameters, which result in the correlation between the two measurements. Note that the $\hbox{$R_{\rm exp}^{\overline{\nu}}$}$ is in agreement with the Standard Model expectation, shown as the point, whereas the $\hbox{$R_{\rm exp}^{\nu}$}$ measurement is not.
• Figure 2: The $\hbox{$R_{\rm exp}$}$ in the neutrino and anti-neutrino beams as a function of the depth of the neutrino interaction within the detector along the beam direction.
• Figure 3: The NuTeV $\hbox{$R_{\rm exp}$}$ binned in square annuli of transverse position from the center to the outer part of the detector. The first four bins are used in this analysis.
• Figure 4: The effect of varying the NuTeV neutral-current/charged-current separation cut on $\hbox{$R_{\rm exp}$}$ in the neutrino (left) and anti-neutrino (right) beams. The error bars represent the statistical uncertainty on the charge. The yellow band is the statistical uncertainty of the ratio as measured from the whole sample.
• Figure 5: The $\hbox{$R_{\rm exp}$}$ as a function of visible energy in the neutrino and anti-neutrino beams. The ratio of data to Monte Carlo is shown below, with a green band to represent the systematic uncertainties in the comparison.