Nuclear model effects in charged-current neutrino-nucleus quasielastic scattering

Abstract

The quasielastic scattering of muon neutrinos on oxygen 16 is studied for neutrino energies between 200 MeV and 1 GeV using a relativistic shell model. Final state interactions are included within the distorted wave impulse approximation, by means of a relativistic optical potential, with and without imaginary part, and of a relativistic mean field potential. For comparison with experimental data the inclusive charged-current quasielastic cross section for − 12 C scattering in the kinematical conditions of the LSND experiment at Los Alamos is also presented and briefly discussed. In the past few years the observation of neutrino oscillations at Super-Kamiokande [1] and the subsequent proposal and realization of new experiments, aimed at determining neutrino properties with high accuracy [2], have renovated the interest towards neutrino scattering on complex nuclei. In fact, neutrino detectors usually contain carbon or oxygen nuclei, and for a proper interpretation of the experimental results the description of the -nucleus interaction must be accurate [3].At intermediate neutrino energies, ranging from some hundreds MeV to a few GeV, -nucleus quasielastic scattering has been studied within several approaches [4]. Relativistic and nonrelativistic studies of random phase approximation have shown nuclear structure effects to be relevant only at low momentum transfers, but indications have been found that for future and precise data analyses of, e.g., atmospheric neutrino measurements, more accurate theoretical estimates may be needed. Additionally, very recently attention has been drawn towards final state interaction (FSI) effects, which, contrary to what is often assumed, may still be relevant even at the relatively high energy E =1 GeV [5].In this contribution we study charged-current (CC) neutrino-nucleus quasielastic scattering within the framework of a relativistic shell model (RSM), already successfully employed to study exclusive electron scattering [6] and neutral current neutrino scattering [7]. We compute inclusive - 16O quasielastic cross sections for three values of the incident neutrino energy, namely, 200 MeV, 500 MeV, and 1 GeV, which are representative of the kinematical range where quasielastic scattering gives the main contribution to the inclusive -nucleus process.We describe the CC quasielastic scattering of neutrinos on a nuclear target within the impulse approximation (IA), assuming that the incident neutrino exchanges one vector boson with only one nucleon, which is then emitted, while the remaining ͑A−1͒ nucleons in the target are spectators. The nuclear current is assumed to be the sum of single-nucleon currents, for which we employ the usual free nucleon expression (see Ref.[7]) with the axial form factor parametrized as a dipole with cutoff mass M A =1.026 GeV [8], and the states of the target and residual nuclei to be adequately described by an independent particle model wave function.To describe the bound nucleon states we use relativistic shell model wave functions, obtained as the se...

Final-state interactions in the superscaling analysis of neutral-current quasielastic neutrino scattering

“…6 in the earlier reference). This result is indeed consistent with the minor role of nuclear modeling expected at energies of the order of 1 GeV and higher [29]. Thus, most of the features concerning the responses at 60 • signaled in Ref.…”

“…In contrast, in the present work, when accounting for FSI between the ejected nucleon and the residual nucleus, the outgoing nucleon wave function is computed by using the same relativistic mean field (RMF) employed to describe the initial bound states. We denote this approach as RMF [3,5,24,25,29,30].…”

“…Besides the RMF, approaches where one uses only the real part of the optical potential [29], or where the full optical potential is employed but a formal summation based on Green function formalism over all possible channels that contribute to the inclusive scattering is done [32,34,35], have been used to describe lepton-nucleus scattering under inclusive conditions. The comparison of results from these approaches show that they differ by a few percent and in general they compare equally well to existing electron scattering data.…”

Inclusive charged-current neutrino-nucleus reactions

“…Simple approaches using a global Fermi gas for the nucleons and the impulse approximation are good enough to describe qualitatively electron scattering but more sophisticated treatments of the nuclear effects are necessary to get a detailed agreement with data. There are different kinds of models like those based on the use of proper nucleon spectral functions [8][9][10], others in which nucleons are treated in a relativistic mean field [11,12] and models based on a local Fermi gas including many body effects such as spectral functions [13] and RPA [2,[14][15][16]. Concerning the elementary process, ν + N → l + N ′ , the hadronic vector current is well known from electron scattering.…”

Construction of spectral functions for medium-mass nuclei

“…There are several approaches to deal with them, e.g., the Wentzel-KramersBrillouin method, relativistic mean-field approach [11], or correlated Glauber approximation [12]. In the previous article [3], we adopted the plane wave impulse approximation (PWIA) and disregarded FSI beyond the Pauli blocking, arguing that this approach is sufficient to describe neutrino scattering.…”