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Neutral-current Neutrino-nucleus Scattering in Quasielastic Region

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 Added by Kyungsik Kim
 Publication date 2007
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and research's language is English




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The neutral-current neutrino-nucleus scattering is calculated through the neutrino-induced knocked-out nucleon process in the quasielastic region by using a relativistic single particle model for the bound and continuum states. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino (antineutrino) scattering on ^{12}C target nucleus. The effects of the final state interaction of the knocked-out nucleon are studied not only on the cross section but also on the asymmetry due to the difference between neutrinos and antineutrinos, within a relativistic optical potential. We also investigate the sensitivity of the strange quark contents in the nucleon on the asymmetry.



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We study the sensitivity of neutral-current neutrino-nucleus scattering to the strange-quark content of the axial-vector form factor of the nucleon. A model-independent formalism for this reaction is developed in terms of eight nuclear structure functions. Taking advantage of the insensitivity of the ratio of proton $( u, u p)$ to neutron $( u, u n)$ yields to distortion effects, we compute all structure functions in a relativistic plane wave impulse approximation approach. Further, by employing the notion of a bound-state nucleon propagator, closed-form, analytic expressions for all nuclear-structure functions are developed in terms of an accurately calibrated relativistic mean-field model. Using a strange-quark contribution to the axial-vector form factor of $g_{A}^{s}=-0.19$, a significant enhancement in the proton-to-neutron yields is observed relative to one with $g_{A}^{s}=0$.
254 - K. S. Kim , Myung Ki Cheoun 2007
Strange quark contributions to the neutral current reaction in the neutrino scattering are investigated on the nucleon level and extended to the $^{12}$C target nucleus through the neutrino-induced knocked-out nucleon process in the quasi-elastic region within the framework of a relativistic single particle model. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino(antineutrino) scattering. Effects of the final state interaction for the knocked-out nucleon are included by a relativistic optical potential. We found that the sensitivity of the strange quark contents could be salient on the asymmetry between neutrino and antineutrino scattering cross sections. In specific, $A ( u ({bar u}), u^{} ({bar u}^{}) N)$ reaction is shown to be very sensitive test in the searches of the strangeness.
We present a model for electron- and neutrino-scattering off nucleons and nuclei focussing on the quasielastic and resonance region. The lepton-nucleon reaction is described within a relativistic formalism that includes, besides quasielastic scattering, the excitation of 13 N* and Delta resonances and a non-resonant single-pion background. Recent electron-scattering data is used for the state-of-the-art parametrizations of the vector form factors; the axial couplings are determined via PCAC and, in the case of the Delta resonance, the axial form factor is refitted using neutrino-scattering data. Scattering off nuclei is treated within the GiBUU framework that takes into account various nuclear effects: the local density approximation for the nuclear ground state, mean-field potentials and in-medium spectral functions. Results for inclusive scattering off Oxygen are presented and, in the case of electron-induced reactions, compared to experimental data and other models.
253 - Chiara Maieron 2006
Nuclear model effects in neutrino-nucleus quasielastic scattering are studied within the distorted wave impulse approximation, using a relativistic shell model to describe the nucleus, and comparing it with the relativistic Fermi gas. Both charged-current and neutral-current processes are considered and, for the neutral-current case, the uncertainties that nuclear effects may introduce in measurements of the axial strange form-factor of the nucleon are investigated.
The axial form factor plays a crucial role in quasielastic neutrino-nucleus scattering, but the error of the theoretical cross section due to uncertainties of $G_A$ remains to be established. Reversely, the extraction of $G_A$ from the neutrino nucleus cross section suffers from large systematic errors due to nuclear model dependencies, while the use of single parameter dipole fits underestimates the errors and prevents an identification of the relevant kinematics for this determination. We propose to use a generalized axial-vector-meson-dominance (AVMD) in conjunction with large-$N_c$ and high energy QCD constrains to model the nucleon axial form factor, as well as the half width rule as an a priori uncertainty estimate. The minimal hadronic ansatz comprises the sum of two monopoles corresponding to the lightest axial-vector mesons being coupled to the axial current. The parameters of the resulting axial form factor are the masses and widths of the two axial mesons as obtained from the averaged PDG values. By applying the half width rule in a Monte Carlo simulation, a distribution of theoretical predictions can then be generated for the neutrino-nucleus quasielastic cross section. We test the model by applying it to the $( u_mu,mu)$ quasielastic cross section from $^{12}$C for the kinematics of the MiniBooNE experiment. The resulting predictions have no free parameters. We find that the relativistic Fermi gas model globally reproduces the experimental data, giving $chi^2/ # bins = 0.81$. A $Q^2$-dependent error analysis of the neutrino data shows that the uncertainties in the axial form factor $G_A(Q^2)$ are comparable to the ones induced by the a priori half width rule. We identify the most sensitive region to be in the range $0.2 lesssim Q^2 lesssim 0.6 ,{rm GeV}^2$.
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