Calculations butkevich 2010 in concert the added

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Unformatted text preview: gations of QE scattering. Axial mass values ranging from 1.05 to 1.35 GeV µ - p) (10-38 cm2 / nucleon) Joseph A. Formaggio and G. P. Zeller: From eV to EeV: Neutrino cross sections . . . 0 -1 10 1 10 10 2 E (GeV) FIG. 11. Existing measurements of the  quasielastic scattering cross section,  n ! À p, as a function of neutrino energy on a variety of nuclear targets. The free nucleon scattering prediction assuming MA ¼ 1:0 GeV is shown for comparison. From Casper (2002). This prediction is altered by nuclear effects in the case of neutrino-nucleus scattering. Care should be taken when interpreting measurements on targets heavier than hydrogen and deuterium. have been recently obtained (Gran et al., 2006; Espinal and Sanchez, 2007; Aguilar-Arevalo, 2008, 2010a; Dorman, 2009; Lyubushkin et al., 2009), with most of the experiments systematically measuring higher MA values than those found in the deuterium fits. This has recently sparked some debate, especially given that higher MA values naturally imply higher cross sections and hence larger event yields for neutrino experiments.10 We return to this point later. Neutrino experiments have also begun to remeasure the absolute QE scattering cross section making use of more reliable incoming neutrino fluxes made available in modern experimental setups. Figure 11 summarizes the existing measurements of  QE scattering cross sections as a function of neutrino energy from both historical and recent measurements. As expected, we observe a linearly rising cross section that is damped by the form factors at higher neutrino energies. What is not expected is the disparity observed between recent measurements. High statistics measurements of the QE scattering cross section by the MiniBooNE (Aguilar-Arevalo et al., 2010a) and NOMAD (Lyubushkin et al., 2009) experiments, both on carbon, appear to differ in normalization by about 30%. The low-energy MiniBooNE results are higher than expected from the Fermi-gas model (Smith and Moniz, 1972) and more sophisticated impulse approximation calculations (Frullani and Mougey, 1984; Maieron et al., 2003; Nieves, Amaro, and Valverde, 2004; Leitner et al., 2006; Martinez et al., 2006; Nieves et al., 2006; Benhar and Meloni, 2007; Ankowski and Sobczyk, 2008; Butkevich, 2009; Leitner et al., 2009; Athar et al., 2010) assuming an axial mass, MA ¼ 1:0 GeV, from deuterium-based measurements as input. How can it be that new, high statistics measurements of this simple process are not coming out as expected? The fact that modern measurements of QE scattering have seemingly 10 Note that modern determinations of MA have largely been obtained from fits to the shape of the observed Q2 distribution of QE events and not their normalization. raised more questions than they have answered has been recently noted (Gallagher, Garvey, and Zeller, 2011; Sobczyk, 2011). It is currently believed that nuclear effects beyond the impulse approximation approach are responsible for the discrepanc...
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