Effects of the density-dependent weak form factors on the neutrino reaction via neutral current for the nucleon in nuclear matter and 12C

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 electroneutrino (nu(e)) and anti-electroneutrino ((v) over bar (e)) reactions with incident energy E-nu <= 80 MeV via neutral current (NC) for a nucleon in a nuclear medium or C-12. For the density-dependent form factors, we exploit the quark-meson-coupling (QMC) model, and apply them to the nu(e) and (nu) over bar (e) induced reactions by NC. About 12% decrease of the total cross section by the nu(e) reaction on the nucleon is obtained at normal density, rho = rho(0) similar to 0.15 fm(-3), as well as about 18% reduction of the total nu(e) cross section on C-12, 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 (nu) over bar (e) reaction reduce significantly the cross sections about 30% for the nucleon in matter and C-12 cases. Such a large asymmetry in the (nu) over bar (e) cross sections is addressed to originate from the different helicities of (nu) over bar (e) and nu(e)