New probe to Ml strengths in GDR region for supernova neutrino interactions

Abstract

The Ml strength (or level density of 1+ states) is of importance for estimation of interaction strengths between neutrinos and nuclei for the study of the supernova neutrino- process. We have proposed a method using (γ, n) reactions with linear polarized laser Compton scattering γ-rays to measure Ml strength. In 1957, Agodi predicted theoretically angular distribution of neutrons emitted from states excited via dipole transitions with linearly polarized γ-ray beam at the polar angle of 8=90° can be described by a simple function, a + b cos(θ2), where θ is azimuthal angel. However, this theoretical prediction has not been verified over the wide mass region. We have measured neutron angular distributions with (polarized gamma, n) reactions on Au, NaI, and Cu. We have verified the Agodi's prediction for the first time over the wide mass region. This suggests that (polarized gamma, n) reactions may be useful tools to study Ml strength in giant resonance regions.