Instances where the theoretical predictions are on a

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Unformatted text preview: o. 3, July–September 2012 As we proceed to other nuclear targets, one immediately appreciates the rarity of this state. 3. Additional nuclear targets The other main nuclear isotope studied in detail is 12 C. There are a number of neutrino interactions on 12 C that have been investigated experimentally e; þ 12 Cg:s: ! ðeÀ ; À Þ þ 12 Ng:s: (51) ðexclusive charged currentÞ; e; þ 12 Cg:s: ! ðeÀ ; À Þ þ 12 NÃ (52) ðinclusive charged currentÞ;  þ 12 Cg:s: !  þ 12 CÃ ðneutral currentÞ: (53) Reaction (51) is a uniquely clean test case for both theory and experiment. The spin parity of the ground state of 12 C is J  ¼ 0þ , T ¼ 0, while for the final state it is J ¼ 1þ , T ¼ 1. As such, there exists both an isospin and spin flip in the interaction, the former involving the isovector components of the reaction, while the latter invoking the axial-vector components. Therefore, both vector and axial-vector components contribute strongly to the interaction. The isovector components are well constrained by electron scattering data. Since the final state of the nucleus is also well defined, the axial form factors can be equally constrained by looking at the decay of 12 N, as well as the muon capture on 12 C. Although these constraints occur at a specific momentum transfer, they provide almost all necessary information to calculate the cross section. The exclusive reaction is also optimal from an experimental perspective. The ground state of 12 N beta decays to the ground state of 12 C with a half-life of 11 ms; the emitted secondary electron providing a well-defined tag for event identification. The neutral-current channel has an TABLE VI. Extraction of the isovector axial two-body current parameter L1;A from various experimental constraints. Method Reactor Solar Helioseismology 3 H ! 3þ He eÀ  "e Extracted L1;A ðfm3 Þ 3:6 Æ 5:5 4:0 Æ 6:3 4:8 Æ 6:7 6:5 Æ 2:4 Joseph A. Formaggio and G. P. Zeller: From eV to EeV: Neutrino cross sections . . . 1321 TABLE VII. Experimentally measured (flux-averaged) cross sections on various nuclei at low energies (1–300 MeV). Experimental data gathered from the LAMPF (Willis et al., 1980), KARMEN (Bodmann et al., 1991; Zeitnitz et al., 1994; Armbruster et al., 1998; Maschuw, 1998; Ruf, 2005), E225 (Krakauer et al., 1992), LSND (Athanassopoulos et al., 1997; Auerbach et al., 2001; Auerbach et al., 2002; Distel et al., 2003), GALLEX (Hampel et al., 1998), and SAGE (Abdurashitov et al., 1999; Abdurashitov et al., 2006) experiments. Stopped = beams can access neutrino energies below 53 MeV, while decay-in-flight measurements can extend up to 300 MeV. The 51 Cr sources have several monoenergetic lines around 430 and 750 keV, while the 37 Ar source has its main monoenergetic emission at E ¼ 811 keV. Selected comparisons to theoretical predictions, using different approaches are also listed. The theoretical predictions are not meant to be exhaustive. Source Experiment Measureme...
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