118501629
Neutrino-nucleus reactions via neutral and charged currents by the quasi-particle random phase approximation (QRPA)
We developed the quasi-particle random phase approximation (QRPA) for neutrino reactions on even–even nuclei via neutral current (NC) and charged current (CC). The QRPA has been successfully applied for nuclear β and ββ decays. To describe neutrino–nucleus reactions, general multipole transitions by the weak interaction with finite momentum transfers are calculated for NC and CC reactions with detailed formulas. Since we consider neutron–proton (np) pairing as well as neutron–neutron (nn) and proton–proton (pp) pairing correlations, the nn + pp QRPA and the np QRPA are combined in a framework, which enables us to describe both NC and CC reactions in a consistent way. Numerical results for ν–12C, –56Fe and –56Ni reactions are shown to match with other theoretical calculations and well reproduce available experimental data.
119821537
The in-medium effects on the neutrino reaction in dense matter
The nucleon form factors in free space are usually thought to be modified when a nucleon is bound in a nucleus or immersed in a nuclear medium. We investigated effects of the density-dependent axial and weak-vector form factors on the electro-neutrino (νe) and anti-electro-neutrino (νe) reactions with incident energy Ev ≤ 80 MeV via neutral current (NC) and charged current (CC) for a nucleon in a nuclear medium or 12C. For the density-dependent form factors, we exploited the quark-meson-coupling (QMC) model, and apply them to the νe and νe induced reactions by NC and CC. In CC reaction, about 5 % decrease of the electro neutrino (νe) reaction cross section on the nucleon is shown to be occurred in normal density, ρ = ρ0∼0.15fm−3, and also about 5 % reduction of total νe cross section on 12C is obtained by the modification of the weak form factors for bound nucleons. Density effects for both cases are relatively small, but they are as large as the effect by the Coulomb distortion of outgoing leptons in t...
121016358
Lifetime of a Nuclear Excited State in Cascade Decay
It is shown that the lifetime of a nuclear excited state in the region of femtoseconds could be accurately measured by a precision measurement facility of a flat crystal spectrometer, if the angular correlation of two successive γ-rays in cascade decay is taken into account in the Doppler shift attenuation method.
119204961
Ambiguities of neutrino (antineutrino) scattering on the nucleon due to the uncertainties of relevant strangeness form factors
Strange quark contributions to the neutrino (antineutrino) scattering on the nucleon level are investigated in the quasi-elastic region. Incident energy is used at 500 MeV for the scattering. All of the physical observables by the scattering are investigated within available experimental and theoretical results for strangeness form factors of the nucleon. Specifically, a newly combined datum of the parity violating electron scattering and the neutrino scattering is exploited for the strangeness form factors. Feasible quantities to be explored for the strangeness contents are discussed for the application to the neutrino–nucleus scattering.
121427481
Investigating the Suppressions for the Longitudinal Structure Function in High Energy Quasielastic Scattering from 56Fe
We investigate the cross sections for inclusive (e, e') reaction from 56 Fe in quasielastic region at large electron energies (2-4GeV) and large three momentum transfer (0.5-1.5 GeV/c). We use a relativistic mean-field single particle model for the bound and continuum nucleon wave functions based on the σ-ω model and we include the effects of electron Coulomb distortion in the calculation. The results are compared to high energy data from SLAC and more recent data from Jefferson Laboratory, particularly for the kinematics where the quasielastic process is expected to dominate the cross section with the energy transfer less than 500 to 600 MeV. The effects of the predicted weakening of the strong scalar and vector potentials of the σ-ω model at high energy are discussed. Possible evidence for "longitudinal suppression" or modifications of nucleon form factors in the medium is considered, but neither is necessary to explain the quasielastic data for four momentum transfers less than 1 (GeV/c) 2 .
116255134
Roles of Direct Break-up Reaction on Neutrino Scattering off $^{12}$C near Nucleon Threshold Region
Neutrino (antineutrino) scattering off $^{12}$C is one of various important key reactions for $\nu$-process in the nucleosysnthesis of light nuclei. Most of neutrino-nucleus scattering are considered through indirect processes within the energy range from a few to tens of MeV. Target nuclei are excited by incident neutrino (antineutrino) through various transitions, and subsequently decay into other nuclei with emitting particles. But, direct processes are also feasible, in which incident neutrino (antineutrino) strips directly one nucleon from target nuclei. Consequently, direct processes may affect abundances of $^{11}$C and $^{11}$B additionally to indirect processes. We investigate direct neutrino (antineutrino) quasi-elastic scattering off $^{12}$C around the energy region liberating one nucleon and discuss implications of direct processes in the nucleosynthesis. The direct processes might be comparable to the indirect processes if the final state interaction is taken into account.
118406337
Coherent/incoherent metal transition in a holographic model
A bstractWe study AC electric (σ), thermoelectric (α), and thermal κ¯$$ \left(\overline{\kappa}\right) $$ conductivities in a holographic model, which is based on 3+1 dimensional Einstein-Maxwell-scalar action. There is momentum relaxation due to massless scalar fields linear to spatial coordinate. The model has three field theory parameters: temperature (T), chemical potential (μ), and effective impurity (β). At low frequencies, if β < μ, all three AC conductivities (σ, α,κ¯$$ \overline{\kappa} $$) exhibit a Drude peak modified by pair creation contribution (coherent metal). The parameters of this modified Drude peak are obtained analytically. In particular, if β ≪ μ the relaxation time of electric conductivity approaches to 23μ/β2$$ 2\sqrt{3\mu }/{\beta}^2 $$ and the modified Drude peak becomes a standard Drude peak. If β > μ the shape of peak deviates from the Drude form (incoherent metal). At intermediate frequencies (T < ω < μ), we have analysed numerical data of three conductivities (σ, α,κ¯$$ \overline{\kappa} $$) for a wide variety of parameters, searching for scaling laws, which are expected from either experimental results on cuprates superconductors or some holographic models. In the model we study, we find no clear signs of scaling behaviour.