Effect of source size and emission time on the p–p momentum correlation function in the two-proton emission process

Abstract

The effect of source size and emission time on the proton–proton (p–p) momentum correlation function ($$C_\mathrm{pp}(q)$$) has been studied systematically. Assuming a spherical Gaussian source with space and time profile according to the function $$S(r,t)\sim \exp (-r^2/2r_{0}^{2}-t/\tau )$$ in the correlation function calculation code (CRAB), the results indicate that one $$C_\mathrm{pp}(q)$$ distribution corresponds to a unique combination of source size $$r_0$$ and emission time $$\tau $$. Considering the possible nuclear deformation from a spherical nucleus, an ellipsoidal Gaussian source characterized by the deformation parameter $$\epsilon =\Delta {R}/R$$ has been simulated. There is almost no difference of $$C_\mathrm{pp}(q)$$ between the results of spherically and ellipsoidally shaped sources with small deformation. These results indicate that a unique source size $$r_0$$ and emission time could be extracted from the p–p momentum correlation function, which is especially important for identifying the mechanism of two-proton emission from proton-rich nuclei. Furthermore, considering the possible existence of cluster structures within a nucleus, the double Gaussian source is assumed. The results show that the p–p momentum correlation function for a source with or without cluster structures has large systematical differences with the variance of $$r_{0}$$ and $$\tau $$. This may provide a possible method for experimentally observing the cluster structures in proton-rich nuclei.