Isovector dipole resonances in {sup 4}He and neutrino-heating in supernova

We studied transition strengths to isovector dipole resonances (GDR‐1¯, SDR‐1¯, and SDR‐2¯) in 4He by using the 4He(7Li,7Beγ) reaction at 455 MeV and by comparing with shell‐model calculations, in order to estimate cross sections of 4He for reactions induced by neutrinos emitting from a thermalized neutrino‐sphere in the type‐II supernova. Excitation of the SDR was dominant in the neutrino‐heating of 4He. The 4He‐excitation via neutral‐current reactions of νμ,τ and νμ,τ was found to be one order of magnitude stronger than that via charged‐current reactions of νe and νe. The total energy‐weighted cross section N for neutrino‐induced neutral‐current reactions on 4He was found to amount to about 1.0×10−40 MeV⋅cm2 which is comparable to those used in the previous simulations. The neutrino‐heating effect of 4He is small in the type‐II supernova explosion.