Photonuclear reaction as a probe for $\alpha$-clustering nuclei in the quasi-deuteron region

Photon-nuclear reaction in a transport model frame, namely an extended quantum molecular dynamics model, has been realized at the photon energy of 70–140 MeV in the quasi-deuteron regime. For an important application, we pay a special focus on photonuclear reactions of ${}^{12}\mathrm{C}(\gamma ,np){}^{10}\mathrm{B}$ where ${}^{12}\mathrm{C}$ is considered as different configurations including $\alpha$ clustering. Obvious differences for some observables have been observed among different configurations, which can be attributed to spatial-momentum correlation of a neutron-proton pair inside nucleus, and therefore it gives us a sensitive probe to distinguish the different configurations including $\alpha$ clustering with the help of the photonuclear reaction mechanism.

Figure 1

Three different configurations of ${}^{12}\mathrm{C}$ were obtained in our EQMD model. (a) chain $3\text{−}\alpha$ structure; (b) triangle $3\text{−}\alpha$ structure; (c) spherical structure without any $\alpha$ cluster.

Figure 2

The recoil momentum spectra of ${}^{12}\mathrm{C}$ with three configurations together with the data (black dot) [43] in three incident photon energy widows.

Figure 3

The missing energy spectra of ${}^{12}\mathrm{C}$ with three configurations in different incident photon energy windows. The solid histograms represent the data and wine curves are the results from the folding spectra derived from ${}^{12}\mathrm{C}(e,e^{{}^{\prime }}p)$ data. For details, see text.

Figure 4

The pair momentum of emitted proton and neutron from three configurations of ${}^{12}\mathrm{C}$ in six photon energy windows.

Figure 5

Same as Fig. 4 but for the opening angular distribution between the emitted neutron and proton.

Figure 6

Hyperangular distribution $\left({\alpha }_3\right)$ of the residual nucleus ${}^{10}\mathrm{B}$ relative to the c.m. of neutron and proton from three-body decay of ${}^{12}\mathrm{C}$ for three configurations. Inserts display the schematic plots for the cases of chain $3\text{−}\alpha$ structure (black) and triangle $3\text{−}\alpha$ structure (red), respectively.

Figure 7

Same as Fig. 6 but for hyper-radius distribution.