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

Abstract

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 $NN\leftrightarrow N\Delta$ reactions in the collision description. As a test of the delta dynamics, the extended AMD is applied to (p,p$'$) recations at $E_{\rm lab}=800$ MeV for a $^{12}$C target. It is found that the ratio and the absolute values for delta peak and quasielastic peak (QEP) in the $^{12}$C(p,p$'$) reaction are reproduced for angles $\Theta_{\rm lab} \agt 40^\circ$, pointing to a correct treatment of the delta dynamics in the extended AMD. For forward angles the QEP is overestimated. 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. As important side results we present a way to apply a Gallilei invariant theory for (N,N$'$) reactions up to $E_{\rm lab} \approx 800$ MeV which ensures approximate Lorentz invariance and we discuss how to fix the width parameter $\nu$ of the single particle momentum distribution for outgoing nucleons in the AMD calculation.