A newly observed state in 12C – characterisation and consequences

D J Marín-Lámbarri,D J Parker,M Freer,C Wheldon,Tz Kokalova

doi:10.1088/1742-6596/569/1/012071

D J Marín-Lámbarri, D J Parker + Show 3 more

Open Access

https://doi.org/10.1088/1742-6596/569/1/012071

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Abstract

Measurements of the 12C(4He,4He)12C* reaction at 40 MeV were performed using a charged-particle detector array composed of four double-sided silicon strip detectors. Resonances in 12 C were reconstructed with the requirement that the a-decay proceeded first via the 8 Be ground state. Of primary significance was the population of the 13.3 and 22.4 MeV resonances, the latter, observed for the first time in this measurement. By using the angular correlation technique the spins of the resonances, have been established as Jπ 4+ and Jπ=5− respectively.

Highlights

Despite all the knowledge acquired over several decades, there are still important details that remain unexplained regarding the nature of the 12C nucleus
The doublesided silicon strip detectors (DSSSDs) do not have explicit particle identication so event selection was achieved through the full kinematic reconstruction allowing the energy and scattering angle of each particle to be determined and, the momentum
The projection of the Dalitz plot is shown in gure 4, in which excited states at 7.654 (0+), 9.641 (3−), 10.844 (1−), 14.083 (4+) MeV are observed

Summary

Introduction

Despite all the knowledge acquired over several decades, there are still important details that remain unexplained regarding the nature of the 12C nucleus. Its second excited state at 7.654 MeV (0+) was rst proposed 61 years ago by Fred Hoyle in order to explain the abundance of 12C in the universe [1]. The structure of the Hoyle state is a signicant open question. It is known to be composed of three α-particles, but the precise arrangement remains unclear. Ab initio calculations suggest the state is congured as a bent-arm [2], in which the three α-particles are located at the vertices of an open triangle. Recent investigations show the existence of a 2+ resonance, which could be a collective rotation or vibration of the Hoyle-state [5, 6]. Some results from the present study have been published in [7]

Experimental Details

Analysis and Results

Angular Correlations

Conclusions

Summary