A stringent upper limit on the direct 3$\alpha$ decay of the Hoyle State in ${}^{12}$C

Abstract

We investigate an implication of the most recent observation of a second $J^{\pi }=2^{+}$ state in ${}^{12}$C, which was measured using the ${}^{12}$C($\gamma$,$\alpha$)${}^8$Be${}_{\text{(g.s.)}}$ reaction. In addition to the dissociation of ${}^{12}$C to an $\alpha$-particle and ${}^8$Be in its ground state, a small fraction of events (2%) were identified as direct decays and decays to excited states in ${}^8$Be. This allowed a limit on the direct 3$\alpha$ partial decay width to be determined as ${\Gamma }_{3\alpha }<32(4)$ keV. Since this 2${}^{+}$ state is predicted by all theoretical models to be a collective excitation of the Hoyle state, the 3$\alpha$ partial width of the Hoyle state is calculable from the ratio of 3$\alpha$ decay penetrabilities of the Hoyle and 2${}^{+}$ states. This was calculated using the semi-classical WKB approach and we deduce a stringent upper limit for the direct decay branching ratio of the Hoyle state of $\frac{{\Gamma }_{3\alpha }}{\Gamma }<5.7\times 10^{-6}$, over an order of magnitude lower than previously reported. This result places the direct measurement of this rare decay mode beyond current experimental capabilities.

arXiv commentAccepted for publication in Physical Review C (Rapid) on 01/16/2020

References in corpus (16)

• Alpha cluster condensation in 12C and 16O
• Ab initio calculation of the Hoyle state
• Microscopic Clustering in Light Nuclei
• Structure of ground and excited states of ${}^{12}$C
• Evidence for Triangular D_3h Symmetry in 12C
• Unambiguous Identification of the Second 2+ State in 12C and the Structure of the Hoyle State
• Concepts of alpha-particle condensation
• The algebraic cluster model. Three-body clusters
• Viability of carbon-based life as a function of the light quark mass
• High precision probe of the fully sequential decay width of the Hoyle state in ${}^{12}$C
• Decay and structure of the Hoyle state
• An Optical Readout TPC (O-TPC) for Studies in Nuclear Astrophysics With Gamma-Ray Beams at HIgS
• Decay Modes of the Hoyle State in ${}^{12}C$
• Anatomy of three-body decay I. Schematic models
• Three-body effects in the Hoyle-state decay
• Dark Matter Bound States: A Window into the Early Universe

Cited by in corpus (10)

• Emergent geometry and duality in the carbon nucleus
• Expanding Nuclear Physics Horizons with the Gamma Factory
• The radiative width of the Hoyle state from $\gamma$-ray spectroscopy
• Almost medium-free measurement of the Hoyle state direct-decay component with a TPC
• Wigner SU(4) symmetry, clustering, and the spectrum of ${}^{12}$C
• Investigating the predicted breathing-mode excitation of the Hoyle state
• Correlation in formation of ${}^8$Be nuclei and $\alpha$-particles in fragmentation of relativistic nuclei
• Machine learning method for ${}^{12}$C event classification and reconstruction in the active target time-projection chamber
• Three-$\alpha$ configurations of the second $J^{\pi }=2^{+}$ state in ${}^{12}$C
• Multi-probe study of excited states in ${}^{12}\mathrm{C}$: disentangling the sources of monopole strength between the Hoyle state and $E_x=13$ MeV