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arXiv · 2312.16861

Search for the 6$\alpha$ condensed state in $^{24}$Mg using the $^{12}\rm{C}+{}^{12}\rm{C}$ scattering

Y. Fujikawa·T. Kawabata·S. Adachi·S. Enyo·T. Furuno·Y. Hijikata·K. Himi·K. Hirose·Y. Honda·K. Inaba·H. Makii·K. Miyamoto·M. Murata·K. Nishio·S. Okamoto·R. Orlandi·K. Sakanashi·F. Suzaki·S. Tsuji·K. Yahiro·J. Zenihiro
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Abstract

We searched for the 6$\alpha$-condensed state in $^{24}$Mg by measuring the $^{12}\rm{C}+{}^{12}\rm{C}$ scattering with the SAKRA Si detector array at $E_\rm{cm}$ = 17.5-25.0 MeV. By using the invariant-mass method for the detected 3$\alpha$ particles, the inclusive cross sections for the $^{12}\rm{C}+{}^{12}\rm{C}\to{}^{12}\rm{C}(0^+_2)+X$ and $^{12}\rm{C}(3^-_1)+X$ reactions were determined. In addition, the missing-mass spectroscopy was successfully utilized to determine the excitation energy of the residual $^{12}\rm{C}$ nucleus and the exclusive cross sections for the $^{12}\rm{C}+{}^{12}\rm{C}\to{}^{12}\rm{C}(0^+_2)+{}^{12}\rm{C}(0^+_1)$, $^{12}\rm{C}(0^+_2)+{}^{12}\rm{C}(2^+_1)$, and $^{12}\rm{C}(0^+_2)+{}^{12}\rm{C}(0^+_2)$ reactions. In both the inclusive $^{12}\rm{C}(0^+_2)+X$ channel and the exclusive $^{12}\rm{C}(0^+_2)+{}^{12}\rm{C}(0^+_1)$ channel, the cross section peaked at $E_rm{cm}$ = 19.4 MeV, which correspond to the excitation energy of $E_x$ = 33.3 MeV in $^{24}\rm{Mg}$. This 19.4-MeV state is a candidate for the 6$\alpha$-condensed state because of the agreement of the excitation energy with the theoretical value and its decay property. In the exclusive $^{12}\rm{C}(0^+_2)+{}^{12}\rm{C}(0^+_2)$ channel, a broad state was observed at $E_\rm{cm}$ = 22.5 MeV, which correspond to the excitation energy of $E_x$ = 36.4 MeV in $^{24}\rm{Mg}$. From the angular distribution of the differential cross section, the spin and parity of this 22.5-MeV state was assigned to be $4^+$. In addition, a $2^+$ state was suggested at the low-energy side of the 22.5-MeV state. Because their excitation energies are higher than the theoretical value of the 6$\alpha$-condensed state, these states might be excited states of the 6$\alpha$-condensed state such as the $2^+_2$ and $4^+_1$ states in $^{12}\rm{C}$.

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Y. Fujikawa, T. Kawabata, S. Adachi, S. Enyo, T. Furuno, Y. Hijikata, K. Himi, K. Hirose, Y. Honda, K. Inaba, H. Makii, K. Miyamoto, M. Murata, K. Nishio, S. Okamoto, R. Orlandi, K. Sakanashi, F. Suzaki, S. Tsuji, K. Yahiro, J. Zenihiro. 2023-12-28. Search for the 6$\alpha$ condensed state in $^{24}$Mg using the $^{12}\rm{C}+{}^{12}\rm{C}$ scattering. https://doi.org/10.1016/j.physletb.2023.138384

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