Delta degrees of freedom in antisymmetrized molecular dynamics and (p,p') reactions in the Delta region.

Abstract

\ensuremath{\Delta} degrees of freedom are introduced into antisymmetrized molecular dynamics (AMD). This is done by increasing the number of basic states in the AMD wave function, introducing a Skyrme-type delta-nucleon potential, and including NN\ensuremath{\leftrightarrows}N\ensuremath{\Delta} reactions in the collision description. As a test of the delta dynamics, the extended AMD is applied to (p,${\mathit{p}}^{\ensuremath{'}}$) reactions at ${\mathit{E}}_{\mathrm{lab}}$=800 MeV for a $^{12}\mathrm{C}$ target. It is found that the ratio and the absolute values for delta peak and quasielastic peak (QEP) in the $^{12}\mathrm{C}$(p,${\mathit{p}}^{\ensuremath{'}}$) reaction are reproduced for angles ${\mathrm{\ensuremath{\Theta}}}_{\mathrm{lab}}$\ensuremath{\gtrsim}40\ifmmode^\circ\else\textdegree\fi{}. For forward angles the QEP is overestimated, but generally the agreement between AMD calculations and experimental data is reasonable. The results of the AMD calculations are compared to one-step Monte Carlo (OSMC) calculations and a detailed analysis of multi-step and delta potential effects is given. Along this analysis a decomposition of the cross section into various reaction channels is presented and the reaction dynamics is discussed in detail. As important side results we present a way to apply a Galilei invariant theory for (N,${\mathit{N}}^{\ensuremath{'}}$) reactions up to ${\mathit{E}}_{\mathrm{lab}}$\ensuremath{\approxeq}800 MeV which ensures approximate Lorentz invariance and we discuss how to fix the width parameter \ensuremath{\nu} of the single particle momentum distribution for outgoing nucleons in the AMD calculation.