Spin determination of particle unstable levels with particle correlations

Particle correlation functions from central ${}^{129}\mathrm{Xe}+{}^{197}\mathrm{Au}$ collisions at $50A\mathrm{MeV}$ have been measured with a large area $\text{silicon}\text{‐}\text{strip}∕\mathrm{Cs}\mathrm{I}$ detector array. A new technique of spin determination from particle correlation functions is proposed. Two examples of correlation functions are studied. The spin of the first excited level of ${}^8\mathrm{B}$ at $0.774\mathrm{MeV}$ is determined as $J=1$.

Figure 1

In the lower panel the density profile of the resonances of ${}^8\mathrm{Be}$ is shown for the $p\text{‐}{}^7\mathrm{Li}$ correlation after subtracting the background shown as the dashed line in the upper panel. The best fit (solid line) is performed by varying the background and the spin value of the $17.64\mathrm{MeV}$ state. Two calculations are shown as the dotted and dot-dashed lines in the upper panel assuming that the spin of the $17.64\mathrm{MeV}$ state is 0 and 2, respectively, and keeping the other parameters the same.

Figure 2

In the left-hand side panel the $p\text{‐}{}^7\mathrm{Be}$ correlation function is fitted by the solid line assuming there are only two states at 0.774 and $2.32\mathrm{MeV}$. The dashed line is the fitted background. The dotted and dot-dashed lines are the calculations assuming that the spin of the $0.774\mathrm{MeV}$ state is 0 and 2, respectively. In the right-hand side panel similar fits are done assuming the existence of an additional state at $1.4\mathrm{MeV}$.