RevModPhys.84.1307

A nucleon or multiple nucleons from the target in the

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Unformatted text preview: resonance state. The resultant baryonic resonance (Á, N Ã ) decays to a variety of possible mesonic final states producing combinations of nucleons and mesons.  Deep inelastic scattering: Given enough energy, the neutrino can resolve the individual quark constituents of the nucleon. This is called deep inelastic scattering and manifests in the creation of a hadronic shower. As a result of these competing processes, the products of neutrino interactions include a variety of final states ranging from the emission of nucleons to more complex final states including pions, kaons, and collections of mesons (Fig. 8). This energy regime is often referred to as the ‘‘transition region’’ because it corresponds to the boundary between quasielastic scattering (in which the target is a nucleon) on the one end and deep inelastic scattering (in which the target is the constituent parton inside the nucleon) on the other. Historically, adequate theoretical descriptions of quasielastic, resonance-mediated, and deep inelastic scattering have been formulated, however, there is no uniform description which Joseph A. Formaggio and G. P. Zeller: From eV to EeV: Neutrino cross sections . . . cm2 / GeV) kaon 0.8 -38 0.7 cross section / E (10 CC (Arbitrary Units) 1 0.9 multi- 0.6 0.5 0.4 1 0.3 0.2 nucleon 0.1 0 0.5 1 1.5 2 2.5 3 3.5 4 1.4 1.2 1 TOTAL 0.8 QE 0.6 DIS 0.4 RES 0.2 0 4.5 10 -1 1 E (GeV) 10 10 2 globally describes the transition between these processes or how they should be combined. Moreover, the full extent to which nuclear effects impact this region is a topic that has only recently been appreciated. Therefore, in this section, we focus on what is currently known, both experimentally and theoretically, about each of the exclusive final-state processes that participate in this region. To start, Fig. 9 summarizes the existing measurements of CC neutrino and antineutrino cross sections across this intermediate energy range  N ! À X; (54)  N ! þ X: " (55) These results have been accumulated over many decades using a variety of neutrino targets and detector technologies. We immediately notice three things from this figure. First, the total cross sections approaches a linear dependence on neutrino energy. This scaling behavior is a prediction of the quark parton model (Feynman, 1969), a topic we return to later, and is expected if pointlike scattering off quarks dominates the scattering mechanism, for example, in the case of deep inelastic scattering. Such assumptions break down, of course, at lower neutrino energies (i.e., lower momentum transfers). Second, the neutrino cross sections at the lower energy end of this region are not typically as well measured as their highenergy counterparts. This is generally due to the lack of high statistics data historically available in this energy range and the challenges that arise when trying to describe all of the various underlying physical processes that can participate in this region. Third, ant...
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This document was uploaded on 09/28/2013.

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