Old and new physics interpretations of 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) L -invariant operator), leptoquarks (not in a minimal way), extra U(1) gauge bosons (maybe: an unmixed Z ′ coupled to B − 3L µ also increases the muon g − 2 by about 10 −9 and gives a 'burst' to cosmic rays above the GZK cutoff).

Electroweak tests at beta-beams

“…However, recent measurement of the neutral-to charged-current ratio in muon antineutrino-nucleon scattering at the NuTEV experiment disagrees with these results by about 3σ [6]. A number of ideas were put forward to explain the so-called NuTEV anomaly, including QCD and nuclear physics effects, extra U(1) gauge bosons, dimension six-operators [7]; universal suppression of Z-neutrino couplings [8]; higher twist effects arising from nuclear shadowing [9]; and sterile neutrino mixing [10]. However, a complete understanding of the physics behind the NuTEV anomaly is still lacking.…”

Precision measurement ofsin2θWat a reactor

“…The study is motivated by the NuTeV result, a 3σ deviation of sin 2 θ W from the Standard Model prediction [1], measured in deep inelastic neutrino scattering (Q 2 = 1 to 140 GeV 2 , Q 2 ν = 26 GeV 2 , Q 2 ν = 15 GeV 2 ). Various Beyond-the-Standard Model explanations have been put forward [2,3,4], and, to fully resolve the issue, many require a follow-up experiment which probes the neutral weak couplings specifically with neutrinos, such as the one described here.This proposed measurement is also interesting as an additional precision study at Q 2 = 4×10 −6 GeV 2 . The two existing low Q 2 measurements are from atomic parity violation (APV) [5], which samples Q 2 ∼ 10 −10 GeV 2 ; and SLAC E158, a Møller scattering experiment at average Q 2 = 0.026 GeV 2 [6].…”

“…The study is motivated by the NuTeV result, a 3σ deviation of sin 2 θ W from the Standard Model prediction [1], measured in deep inelastic neutrino scattering (Q 2 = 1 to 140 GeV 2 , Q 2 ν = 26 GeV 2 , Q 2 ν = 15 GeV 2 ). Various Beyond-the-Standard Model explanations have been put forward [2, 3,4], and, to fully resolve the issue, many require a follow-up experiment which probes the neutral weak couplings specifically with neutrinos, such as the one described here.…”

New physics searches at near detectors of neutrino oscillation experiments

“…There are several such operators [16][17][18][19][20][21][22][23][24][25], depending on the production mechanism of the neutrino beam (π decay for conventional neutrino beams and super-beam experiments, β decay for β-beam and reactor experiments and µ decays for neutrino factories). We will classify the new physics operators in three different categories:…”

“…The operator O ED can be decomposed into the following fundamental interactions through mediator fields [17][18][19]: In an explicit model to realise the 2L2Q operators, possible additional constraints would have to be taken into account and it is an interesting question whether the modelindependent bounds derived in this study can be saturated in such a model. Similar types of models, and their phenomenological constraints, have been studied in the literature.…”