Missing monopole strength of the Hoyle state in the inelastic $\alpha$+${}^{12}$C scattering

Abstract

Analyses of the inelastic $\alpha$+${}^{12}$C scattering at medium energies have indicated that the strength of the Hoyle state (the isoscalar 0${}_2^{+}$ excitation at 7.65 MeV in ${}^{12}$C) seems to exhaust only 7 to 9% of the monopole energy weighted sum rule (EWSR), compared to about 15% of the EWSR extracted from inelastic electron scattering data. The full monopole transition strength predicted by realistic microscopic $\alpha$-cluster models of the Hoyle state can be shown to exhaust up to 22% of the EWSR. To explore the missing monopole strength in the inelastic $\alpha$+${}^{12}$C scattering, we have performed a fully microscopic folding model analysis of the inelastic $\alpha$+${}^{12}$C scattering at $E_{\mathrm{lab}}=104$ to 240 MeV using the 3-$\alpha$ resonating group wave function of the Hoyle state obtained by Kamimura, and a complex density-dependent M3Y interaction newly parametrized based on the Brueckner Hartree Fock results for nuclear matter. Our folding model analysis has shown consistently that the missing monopole strength of the Hoyle state is not associated with the uncertainties in the analysis of the $\alpha$+${}^{12}$C scattering, but is most likely due to the short lifetime and weakly bound structure of this state which significantly enhances absorption in the exit $\alpha$+${}^{12}$C${}^{\ast }(0_2^{+})$ channel.

arXiv commentAccepted for publication in Physics Letters B

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Cited by in corpus (14)

• Coupled-channels calculations for nuclear reactions: from exotic nuclei to superheavy elements
• Microscopic optical potentials for ${}^4$He scattering
• Alpha-cluster Condensations in Nuclei and Experimental Approaches for their Studies
• Hindrance of the excitation of the Hoyle state and the ghost of the $2_2^{+}$ state in ${}^{12}$C
• Consistency between the monopole strength of the Hoyle state determined by structural calculation and that extracted from reaction observables
• $\alpha$ scattering cross sections on ${}^{12}$C with microscopic coupled-channel calculation
• Folding model analysis of the inelastic $\alpha {+}^{12}$C scattering at medium energies, and the isoscalar transition strengths of the cluster states of ${}^{12}$C
• Direct and indirect $\alpha$ transfer in the elastic ${}^{16}$O+${}^{12}$C scattering
• Microscopic coupled-channel calculations of nucleus-nucleus scattering including chiral three-nucleon-force effects
• A microscopic approach to ${}^3$He scattering
• Microscopic study of the isoscalar giant resonances in 208Pb induced by inelastic alpha scattering
• First microscopic coupled-channel calculation of $\alpha$ inelastic cross sections on ${}^{16}$O
• Probing the isoscalar excitations of 12C with inelastic alpha scattering
• Low-energy ${}^{12}$C continuum states in three-$\alpha$ model