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Register a new userNuclear dependence of the 2p2h electroweak response in the Relativistic Fermi Gas model
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We present the results of a recent study of meson-exchange two-body currents in lepton-nucleus inclusive scattering at various kinematics and for different nuclei within the Relativistic Fermi Gas model. We show that the associated nuclear response functions at their peaks scale as $A k_F^2$, for Fermi momentum $k_F$ going from 200 to 300 MeV/c and momentum transfer $q$ from $2k_F$ to 2 GeV/c. This behavior is different from what is found for the quasielastic response, which scales as $A/k_F$. This result can be valuable in the analyses of long-baseline neutrino oscillation experiments, which need to implement these nuclear effects in Monte Carlo simulations for different kinematics and nuclear targets.
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The electroweak response functions for inclusive electron scattering are calculated in the Relativistic Fermi Gas model, both in the quasi-elastic and in the $Delta$ peak regions. The impact of relativistic kinematics at high momentum transfer is investigated through an expansion in the initial nucleonic momentum, which is however exact in the four-momentum of the exchanged boson. The same expansion is applied to the meson exchange currents in the particle-hole sector: it is shown that the non-relativistic currents can be corrected by simple kinematical factors to account for relativity. The left-right asymmetry measured via polarized electron scattering is finally evaluated in the quasi-elastic and $Delta$ peaks.
We develop an asymmetric relativistic Fermi gas model for the study of the electroweak nuclear response in the quasielastic region. The model takes into account the differences between neutron and proton densities in asymmetric (N > Z) nuclei, as well as differences in the neutron and proton separation energies. We present numerical results for both neutral and charged current processes, focusing on nuclei of interest for ongoing and future neutrino oscillation experiments. We point out some important differences with respect to the commonly employed symmetric Fermi gas model.
The self-consistent proton-neutron quasiparticle random phase approximation approach is employed to calculate $beta$-decay half-lives of neutron-rich even-even nuclei with $8leqslant Z leqslant 30$. A newly proposed nonlinear point-coupling effective interaction PC-PK1 is used in the calculations. It is found that the isoscalar proton-neutron pairing interaction can significantly reduce $beta$-decay half-lives. With an isospin-dependent isoscalar proton-neutron pairing strength, our results well reproduce the experimental $beta$-decay half-lives, although the pairing strength is not adjusted using the half-lives calculated in this study.
The short-range and tensor components of the bare nucleon-nucleon interaction induce a sizeable depletion of low momenta in the ground state of a nuclear many-body system. The self-consistent Greens function method within the ladder approximation provides an textit{ab-initio} description of correlated nuclear systems that accounts properly for these effects. The momentum distribution predicted by this approach is analyzed in detail, with emphasis on the depletion of the lowest momentum state. The temperature, density, and nucleon asymmetry (isospin) dependence of the depletion of the Fermi sea is clarified. A connection is established between the momentum distribution and the time-ordered components of the self-energy, which allows for an improved interpretation of the results. The dependence on the underlying nucleon-nucleon interaction provides quantitative estimates of the importance of short-range and tensor correlations in nuclear systems.
The presence of a resonant structure corresponding to the $Delta$ excitation in the longitudinal response to an e.m. probe is investigated. It is shown that many-body effects could significantly increase the relativistic contribution suggested by M.Ericson and coworkers
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