![]() ![]() The initial and final states of the struck nucleon are shown as u( p) and u( p′), where only the magnitude of the nucleon momentum is explicit and the spin and isospin states are suppressed. The superscripts S and V refer to the isoscalar and isovector contributions. where M is the proton mass and μ′ p and μ n are the anomalous magnetic moments of the proton and neutron τ 3 is +1 for the proton and −1 for the neutron. The extent to which each of these two scenarios describes what is observed experimentally is a focus of this review.Ģ. In reality, the nucleons are not independent particles, and as a result, more complex nuclear dynamics are involved. In the simplest and most common scenario, neutrino-nucleus scattering is treated as the incoherent sum of scattering from free nucleons, the so-called impulse-approximation approach. For elastic scattering (or what is known as QE scattering in the case of charged-current neutrino scattering), the former is well established, and the latter has been the subject of much theoretical and experimental work in the context of lepton scattering over the past 40 years ( Figure 1). The simplest description of neutrino-nuclear scattering is built upon two ingredients: a characterization of neutrino-nucleon scattering and a model for nucleons in the nucleus. 2. QUASI-ELASTIC LEPTON-NUCLEUS SCATTERING: PRELIMINARIES We conclude with a commentary on future directions. In this article, we review the standard picture of QE scattering, drawing heavily on the analogous electro-nuclear scattering processes summarize measurements of neutrino QE scattering and present ideas about additional nuclear effects that may play a role in the interpretation of this data. Neutrino-nucleus QE scattering has been the focus of substantial work over the past 40 years, and comparisons between recent results and those from the bubble-chamber era reveal differences that challenge our assumptions regarding these processes. The complexities exposed here are present in other channels. 1.įuture high-statistics oscillation experiments, in particular those that use QE events as their signal sample to investigate neutrino oscillations, will require a thorough understanding of this region.Īlthough neutrino-nucleon QE scattering is well characterized, when this process occurs within the nucleus, the description becomes more complicated. We restrict our focus for several reasons. ![]() This article focuses on medium-energy neutrino-nucleus interactions (∼0.3 < E ν < 3.0 GeV), with particular emphasis on quasi-elastic (QE) neutrino scattering-the simplest and most copious interaction at these energies. At high energies, O(100 GeV), the scale for deep-inelastic scattering (DIS) becomes partonic (∼0.1 fm), and nuclear effects, although present, are less significant. ![]() These are the interactions of greatest interest to atmospheric and accelerator-based neutrino oscillation experiments. In the medium-energy regime, O(1 GeV), which constitutes the bulk of this review, the interaction length is hadronic ∼(1 fm), with important nuclear effects. These are the interactions of greatest interest to solar and reactor neutrino oscillation experiments. At low energy, O(MeV), the wavelength scale of the interaction is greater than the nuclear diameter so that the initial and final states are specific nuclear levels. Such interactions readily separate into three distinct topical areas that can be classified as low, medium, and high energy. ![]() Over the past decade, the discovery and study of neutrino oscillations have renewed interest in neutrino-nucleus interactions. ![]()
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