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Register a new userInelastic neutrino and antineutrino scattering on nuclei and ``strangeness of the nucleon
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Possibilities to extract information on the strange form factors of the nucleon from neutrino (antineutrino) inelastic scattering on nuclei, in an energy range from 200 MeV to 1 GeV and more, are investigated in detail. All calculations are performed within two relativistic independent particle models (Fermi gas and shell model); the final state interactions of the ejected nucleon are taken into account through relativistic optical model potentials. We have shown that the values of the cross sections significantly depend on the nuclear model (especially in the lower energy range). However the NC/CC neutrino-antineutrino asymmetry in a medium--high energy range shows a rather small dependence on the model and allows to disentangle different values of the parameters that characterize the strange form factors. We have calculated also the ratio of the cross sections for inelastic NC scattering of neutrinos on nuclei, with the emission of a proton and of a neutron. Our calculations show that this ratio depends rather weakly on the nuclear model and confirm previous conclusions on the rather strong dependence of this ratio upon the axial strange form factors.
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Neutrino-nucleus $ u Ato u A$ and antineutrino-nucleus $bar u Ato bar u A$ interactions, when the nucleus conserves its integrity, are discussed with coherent (elastic) and incoherent (inelastic) scattering regimes taken into account. In the first regime the nucleus remains in the same quantum state after the scattering and the cross-section depends on the quadratic number of nucleons. In the second regime the nucleus changes its quantum state and the cross-section has an essentially linear dependence on the number of nucleons. The coherent and incoherent cross-sections are driven by a nuclear nucleon form-factor squared $|F|^2$ term and a $(1-|F|^2)$ term, respectively. One has a smooth transition between the regimes of coherent and incoherent (anti)neutrino-nucleus scattering. Due to the neutral current nature these elastic and inelastic processes are indistinguishable if the nucleus recoil energy is only observed. One way to separate the coherent signal from the incoherent one is to register $gamma$ quanta from deexcitation of the nucleus excited during the incoherent scattering. Another way is to use a very low-energy threshold detector and collect data at very low recoil energies, where the incoherent scattering is vanishingly small. In particular, for ${}^{133}text{Cs}$ and neutrino energies of 30--50 MeV the incoherent cross-section is about 15-20% of the coherent one. Therefore, the COHERENT experiment (with ${}^{133}text{Cs}$) has measured the coherent elastic neutrino nucleus scattering (CE$ u$NS) with the inelastic admixture at a level of 15-20%, if the excitation $gamma$ quantum escapes its detection.
We calculate the ratio of proton and neutron yields in NC induced neutrino(antineutrino)-nucleus inelastic scattering at neutrino energies of about 1 GeV. We show that this ratio depends very weakly on the nuclear models employed and that in the neutrino and antineutrino cases the ratios have different sensitivity to the axial and vector strange form factors; moreover, the ratio of antineutrino--nucleus cross sections turns out to be rather sensitive to the electric strange form factor. We demonstrate that measurements of these ratios will allow to get information on the strange form factors of the nucleon in the region Q > 0.4 GeV^2.
In $ u/bar{ u}$-N/A interactions SIS is technically defined in terms of the four-momentum transfer to the hadronic system as non-resonant meson production with $Q^2 lessapprox 1~GeV^2$. This non-resonant meson production intermixes with resonant meson production in a regime of similar effective hadronic mass W of the interaction. As $Q^2$ grows and surpasses this $approx 1~GeV^2$ limit, non-resonant interactions begin to take place with quarks within the nucleon indicating the start of DIS region. SIS and DIS regions have received varying degrees of attention from the community. While the theoretical / phenomenological study of $ u$-nucleon and $ u$-nucleus DIS scattering is advanced, such studies of a large portion of the SIS region, particularly the SIS to DIS transition region, have hardly begun. Experimentally, the SIS and the DIS regions for $ u$-nucleon scattering have minimal results and only in the experimental study of the $ u$-nucleus DIS region are there significant results for some nuclei. Since current and future neutrino oscillation experiments have contributions from both higher W SIS and DIS kinematic regions and these regions are in need of both considerable theoretical and experimental study, this review will concentrate on these SIS to DIS transition and DIS kinematic regions surveying our knowledge and the current challenges.
A status report is given for a joint project of the Budapest-Marseille-Wuppertal collaboration and the Regensburg group to study the quark mass-dependence of octet baryons in SU(3) Baryon XPT. This formulation is expected to extend to larger masses than Heavy-Baryon XPT. Its applicability is tested with 2+1 flavor data which cover three lattice spacings and pion masses down to about 190 MeV, in large volumes. Also polynomial and rational interpolations in M_pi^2 and M_K^2 are used to assess the uncertainty due to the ansatz. Both frameworks are combined to explore the precision to be expected in a controlled determination of the nucleon sigma term and strangeness content.
The charged-current double differential neutrino cross section, measured by the MiniBooNE Collaboration, has been analyzed using a microscopical model that accounts for, among other nuclear effects, long range nuclear (RPA) correlations and multinucleon scattering. We find that MiniBooNE data are fully compatible with the world average of the nucleon axial mass in contrast with several previous analyses which have suggested an anomalously large value. We also discuss the reliability of the algorithm used to estimate the neutrino energy.
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