Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Old and new physics interpretations of the NuTeV anomaly

S. Davidson, S. Forte, P. Gambino, N. Rius, A. Strumia

TL;DR

The paper assesses whether the NuTeV NC/CC anomaly can be reconciled with the Standard Model via QCD effects (notably a strange sea asymmetry and possible isospin breaking) or requires new physics. It systematically evaluates oblique corrections, modified gauge couplings, MSSM loop effects, and nonrenormalizable operators, concluding that QCD uncertainties can account for a substantial portion of the discrepancy, while oblique or simple coupling shifts fall short. Among new-physics options, dimension-6 operators and, in particular, certain SU(2)L-invariant forms, or leptoquark or Z' scenarios, can explain the data within broader experimental constraints, with distinctive predictions testable at colliders or in precision observables. The work highlights the interplay between hadronic structure and beyond-Standard-Model possibilities, and emphasizes the need for improved PDFs and a full NLO treatment to definitively resolve the NuTeV anomaly.

Abstract

We discuss whether the NuTeV anomaly can be explained, compatibly with all other data, by QCD effects (maybe, if the strange sea is asymmetric, or there is a tiny violation of isospin), new physics in propagators or couplings of the vector bosons (not really), loops of supersymmetric particles (no), dimension six operators (yes, for one specific SU(2)-invariant operator), leptoquarks (not in a minimal way), extra U(1) gauge bosons (maybe: an unmixed Z' coupled to B-3L_mu also increases the muon g-2 by about 10^{-9} and gives a `burst' to cosmic rays above the GZK cutoff).

Old and new physics interpretations of the NuTeV anomaly

TL;DR

The paper assesses whether the NuTeV NC/CC anomaly can be reconciled with the Standard Model via QCD effects (notably a strange sea asymmetry and possible isospin breaking) or requires new physics. It systematically evaluates oblique corrections, modified gauge couplings, MSSM loop effects, and nonrenormalizable operators, concluding that QCD uncertainties can account for a substantial portion of the discrepancy, while oblique or simple coupling shifts fall short. Among new-physics options, dimension-6 operators and, in particular, certain SU(2)L-invariant forms, or leptoquark or Z' scenarios, can explain the data within broader experimental constraints, with distinctive predictions testable at colliders or in precision observables. The work highlights the interplay between hadronic structure and beyond-Standard-Model possibilities, and emphasizes the need for improved PDFs and a full NLO treatment to definitively resolve the NuTeV anomaly.

Abstract

We discuss whether the NuTeV anomaly can be explained, compatibly with all other data, by QCD effects (maybe, if the strange sea is asymmetric, or there is a tiny violation of isospin), new physics in propagators or couplings of the vector bosons (not really), loops of supersymmetric particles (no), dimension six operators (yes, for one specific SU(2)-invariant operator), leptoquarks (not in a minimal way), extra U(1) gauge bosons (maybe: an unmixed Z' coupled to B-3L_mu also increases the muon g-2 by about 10^{-9} and gives a `burst' to cosmic rays above the GZK cutoff).

Paper Structure

This paper contains 13 sections, 33 equations, 2 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The SM prediction
  3. QCD corrections
  4. Oblique corrections
  5. Corrections to gauge boson interactions
  6. Loop effects in the MSSM
  7. Non renormalizable operators
  8. Leptoquarks
  9. Unmixed extra U(1) $Z'$ boson
  10. Summary
  11. Acknowledgments
  12. Note added
  13. Note added after publication (June 2002)

Figures (2)

  • Figure 1: The SM prediction for ($g_L^2, g_R^2$) at $68,99\%$ CL and the NuTeV determination, at $68,90,99\%$ CL. The crosses show how the NuTeV central value moves along the PW line using different sets of parton distribution functions that assume $s=\bar{s}$. If $s>\bar{s}$ the PW line is shifted towards the SM prediction.
  • Figure 3: Shifts in $g_{L,R}^2$ in the supersymmetric scenario described in the text (light sleptons and gauginos) for points in the parameter space which are not excluded by experimental constraints.