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Register a new userEffects of medium modifications of nucleon form factors on neutrino scattering in dense matter
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Effects of the in-medium modifications of nucleon form factors on neutrino interaction in dense matter are presented by considering both the weak and electromagnetic interactions of neutrinos with the constituents of the matter. A relativistic mean field and the quark-meson coupling models are respectively adopted for the effective nucleon mass and in-medium nucleon form factors. We calculate the cross-section of neutrino scattering as well as the neutrino mean free path. We found the cross sections of neutrino scattering in cold nuclear medium decreases when the in-medium modifications of the nucleon weak and electromagnetic form factors are taken into account.This reduction results in the enhancement of the neutrino mean free path, in particular at the baryon density of around a few times of the normal nuclear matter density.
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We use the Nambu-Jona-Lasinio model as an effective quark theory to investigate the medium modifications of the nucleon electromagnetic form factors. By using the equation of state of nuclear matter derived in this model, we discuss the results based on the naive quark-scalar diquark picture, the effects of finite diquark size, and the meson cloud around the constituent quarks. We apply this description to the longitudinal response function for quasielastic electron scattering. RPA correlations, based on the nucleon-nucleon interaction derived in the same model, are also taken into account in the calculation of the response function.
Effects of neutrino charge radius and magnetic moment, as well as the medium modifications of the weak and electromagnetic nucleon form factors of the constituents of matter on the neutrino electroweak interaction with dense nuclear matter, are estimated. A relativistic mean-field and quark-meson coupling models are adopted for the in-medium effective nucleon mass and nucleon form factors. We find that the neutrino scattering cross section increases in the cold nuclear medium when neutrino form factors and the in-medium modifications of the nucleon weak and electromagnetic form factors are simultaneously taken into account relative to that without neutrino form factors. The increase of the cross section results in the decrease of the neutrino mean free path, particularly at larger neutrino magnetic moment and charge radius. The quenching of the neutrino mean free path is estimated to be about 12-58% for the values of $mu_ u = 3 times 10^{-12} mu_B$ and $R_ u = 3.5 times 10^{-5}~textrm{MeV}^{-1}$, obtained from the constraints of the astrophysical observations, compared to that of $mu_ u =0$ and $R_ u =0$. The decrease of the neutrino mean free path is expected to decelerate the cooling of neutron stars. Each contribution of the neutrino form factors to the neutrino mean free path is discussed.
Strange quark contributions to neutrino(antineutrino) scattering are investigated on the nucleon level in the quasi-elastic region. The incident energy range between 500 MeV and 1.0 GeV is used for the scattering. All of the physical observable by the scattering are investigated within available experimental and theoretical results for the strangeness form factors of the nucleon. In specific, a newly combined data of parity violating electron scattering and neutrino scattering is exploited. Feasible quantities to be explored for the strangeness contents are discussed for the application to neutrino-nucleus scattering.
A dressed-quark core contribution to nucleon electromagnetic form factors is calculated. It is defined by the solution of a Poincare covariant Faddeev equation in which dressed-quarks provide the elementary degree of freedom and correlations between them are expressed via diquarks. The nucleon-photon vertex involves a single parameter; i.e., a diquark charge radius. It is argued to be commensurate with the pions charge radius. A comprehensive analysis and explanation of the form factors is built upon this foundation. A particular feature of the study is a separation of form factor contributions into those from different diagram types and correlation sectors, and subsequently a flavour separation for each of these. Amongst the extensive body of results that one could highlight are: r_1^{n,u}>r_1^{n,d}, owing to the presence of axial-vector quark-quark correlations; and for both the neutron and proton the ratio of Sachs electric and magnetic form factors possesses a zero.
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 investigate effects of the density-dependent axial and weak-vector form factors on the electro-neutrino ($ u_e$) and anti-electro-neutrino $({bar u_e})$ reactions via neutral current (NC) for a nucleon in nuclear medium or $^{12}$C. For the density-dependent form factors, we exploit the quark-meson-coupling (QMC) model, and apply them to the $ u_e$ and ${bar u_e}$ induced reactions by NC. About 12% decrease of the total cross section by $ u_e$ reaction on the nucleon is obtained at normal density, $rho = rho_0 sim 0.15 {fm}^{-3} $, as well as about 18% reduction of total ${ u}_e$ cross section on $^{12}$C, by the modification of the weak form factors of the bound nucleon. However, similarly to the charged current reaction, effects of the nucleon property change in the ${bar u}_e$ reaction reduce significantly the cross sections about 30% for the nucleon in matter and $^{12}$C cases. Such a large asymmetry in the ${bar u}_e$ cross sections is addressed to originate from the different helicities of ${bar u}_e$ and ${ u}_e$.
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