Search for Delta^++ component in 12^C ground state using 12^C(gamma, pi^+ p) reaction

Abstract

The differential cross section for the $^{12}$C$(\gamma,\pi^{+}p)$ reaction has been measured in the $\Delta$(1232) resonance region at high recoil momenta of the residual nuclear system. The data are analyzed under the assumption that the formation of the $\pi^+p$ pairs may be interpreted as a $\gamma\Delta^{++}\to\pi^+p$ process which takes place on a $\Delta^{++}$ preexisting in the target nucleus. Estimates of the $\Delta^{++}$ momentum distribution $\rho_{\Delta^{++}}(\bar{p})$=0.17 fm$^3$ for a mean momentum $\bar{p}=300\pm49$ MeV/c as well as the number of $\Delta$ isobars per nucleon $N_\Delta=0.017$ were obtained for $^{12}$C.