ROPER EXCITATION IN ALPHA-PROTON SCATTERING

We study the Roper excitation in the (alpha,alpha') reaction. We consi der all processes which may be relevant in the Roper excitation region , namely, Roper excitation in the target, Roper excitation in the proj ectile, and double Delta excitation processes. The theoretical investi gation shows that the Roper excitation in the proton target mediated b y an isoscalar exchange is the dominant mechanism in the process. We d etermine an effective isoscalar interaction by means of which the expe rimental cross section is well reproduced. This should be useful to ma ke predictions in related reactions and is a first step to construct e ventually a microscopic NN-->NN transition potential, for which the p resent reaction does not offer enough information.