Inclusive neutron cross sections from Ne-Pb collisions at 790 MeV/nucleon.

Abstract

Inclusive neutron spectra were measured at 0\ifmmode^\circ\else\textdegree\fi{}, 15\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}, 50\ifmmode^\circ\else\textdegree\fi{}, 70\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, 120\ifmmode^\circ\else\textdegree\fi{}, and 160\ifmmode^\circ\else\textdegree\fi{} from Ne-Pb collisions at 790 MeV/nucleon. A peak that originates from neutron evaporation from the projectile appears in the spectra at 0\ifmmode^\circ\else\textdegree\fi{}. The shapes and magnitudes of the spectra are compared with those calculated from models of nucleus-nucleus collisions. The Boltzmann-Uehling-Uhlenbeck (BUU), intranuclear cascade (INC), and firestreak models agree generally with the measured double-differential cross sections and particularly at 50\ifmmode^\circ\else\textdegree\fi{} and beyond; however, none of the models can reproduce the peaks at small angles (\ensuremath{\theta}\ensuremath{\le}15\ifmmode^\circ\else\textdegree\fi{}). The quantum molecular dynamics (QMD) model underestimates the spectra of the double-differential cross sections at all angles and energies for this asymmetric system. Also, the predictions of the INC model agrees with the angular distribution of the differential cross sections except that it underestimates the cross section at 0\ifmmode^\circ\else\textdegree\fi{}; the BUU prediction overestimates the differential cross section at 0\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{}; firestreak overpredicts at 15\ifmmode^\circ\else\textdegree\fi{} and 30\ifmmode^\circ\else\textdegree\fi{} and underpredicts at 70\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{}; and the QMD model underpredicts the measured angular distribution and the energy spectra at forward angles.