Nuclear Theory·nucl-th
10 papers—6 primary·4 cross-listed
Vladimir Gudkov🇺🇸 · Hirohiko M. Shimizu🇯🇵
A general theory of pseudomagnetic effects for the propagation of polarized neutrons through polarized target in multi resonance approach is presented. Some applications related to the proposed search for time reversal invariance violation in neutron scattering are considered.
Takayuki Myo · Hiroshi Toki · Kiyomi Ikeda · Hisashi Horiuchi · Tadahiro Suhara
We study the tensor-optimized antisymmetrized molecular dynamics (TOAMD) as a successive variational method in many-body systems with strong interaction for nuclei. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiples are operated to the AMD state as the variational wave function. The total wave function is expressed as the sum of all the components and the variational space can be increased successively with the multiple correlation functions to achieve convergence. All the necessary matrix elements of many-body operators, consisting of the multiple correlation functions and the Hamiltonian, are expressed analytically using the Gaussian integral formula. In this paper we show the results of TOAMD with up to the double products of the correlation functions for the s-shell nuclei, 3H and 4He, using the nucleon-nucleon interaction AV8'. It is found that the energies and Hamiltonian components of two nuclei converge rapidly with respect to the multiple of correlation functions. This result indicates the efficiency of TOAMD for the power series expansion in terms of the tensor and short-range correlation functions.
Some recent progress and open questions in extracting and understanding the new physics underlying the density dependence of nuclear symmetry energy from laboratory experiments are discussed.
A review is given of our present knowledge of different parametrization of experimental results in inelastic scattering process with polarized proton beams. Spin observables in inelastic proton scattering for a set of lightweight nuclei are studied at intermediate energies in the region of 100-500 MeV. Two important types of DWIA calculations are used in the analysis of experiments. Important spin observables representing the difference functions (P-Ay) and (P-Ay)sigma are examined along with the polarization-transfer (spin-transfer) coefficients D(ij), i.e. D with indices NN, SS, LL, LS and SL, in inelastic scattering of polarized protons. The above indicated value of sigma is the differential cross section. These spin observables are treated in the context of the exchange features of the effective interaction. The linear combinations D(K), D(i) of the complete polarization-transfer observables D(ij) in inelastic proton scattering at intermediate energies are extensively demonstrated. A comparison between systematized, measured and calculated quantities of the combinations D(K) and, partially, sigma D(K) for the 1+ (T=0 and T=1) levels in 12-C, for the 4- (T=0 and T=1) states in 16-O, and for the 6- (T=0 and T=1) levels in 28-Si are reported. Particularities in angular distributions of transverse- and longitudinal-spin-transfer probabilities D(K) for T=0 and T=1 unnatural-parity states in some nuclei are discussed. The spin-observable combinations D(Ls) allowed to differentiate reliably the strength of isoscalar and isovector spin-orbit. interactions. The comparison of the experimental and calculated D(K) for the 1+, T = 0 state in 12- C with the use of zero-range treatment (LEA code) and exact finite-range calculations (DWBA-91 program) made it possible to identify the role of exchange contributions. Other observables are also considered for the same purposes.
Juan Nieves🇪🇸 · Joanna Ewa Sobczyk🇵🇱
In a well-established many-body framework, successful in modeling a great variety of nuclear processes, we analyze the role of the spectral functions (SFs) accounting for the modifications of the dispersion relation of nucleons embedded in a nuclear medium. We concentrate in processes mostly governed by one-body mechanisms, and study possible approximations to evaluate the particle-hole propagator using SFs. We also investigate how to include together SFs and long-range RPA-correlation corrections in the evaluation of nuclear response functions, discussing the existing interplay between both type of nuclear effects. At low energy transfers (\le 50 MeV), we compare our predictions for inclusive muon and radiative pion captures in nuclei, and charge-current (CC) neutrino-nucleus cross sections with experimental results. We also present an analysis of intermediate energy quasi-elastic neutrino scattering for various targets and both neutrino and antineutrino CC driven processes. In all cases, we pay special attention to estimate the uncertainties affecting the theoretical predictions. In particular, we show that errors on the \sigma_{\mu}/\sigma_e ratio are much smaller than 5%, and also much smaller than the size of the SF+RPA nuclear corrections, which produce significant effects, not only in the individual cross sections, but also in their ratio for neutrino energies below 400 MeV. These latter nuclear corrections, beyond Pauli blocking, turn out to be thus essential to achieve a correct theoretical understanding of this ratio of cross sections of interest for appearance neutrino oscillation experiments. We also briefly compare our SF and RPA results to predictions obtained within other representative approaches.
The deformation parameters beta and gamma together with the two-quasiparticle excitations are taken into account, for the first time, as coordinates within a symmetry conserving (angular momentum and particle number) generator coordinate method. The simultaneous consideration of collective as well as single particle degrees of freedom allows us to describe soft and rigid nuclei as well as the transition region in between. We apply the new theory to the study of the spectra and transition probabilities of the 156-172Er isotopes with a Pairing plus Quadrupole residual interaction. Good agreement with the experimental results is obtained for most of the observables studied and with the same quality for the very soft and the strongly deformed nuclei.
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