Orateur
Prof.
Oleg O. I. Kartavtsev
(Dubna, Russia)
Description
During the recent years, there is a continuous interest to the experimental and theoretical
study of the 12 C nucleus [1, 2, 3, 4]. In this respect, of special importance is the description
of the Hoyle state, which was predicted more then 50 years ago merely from the abundance
of elements in the universe. Whereas the Hoyle state is fairly well studied experimentally,
e. g., its extremely small width Γ and Hoyle to ground-state transition density (in particular,
the monopole transition matrix element M12 and the transition radius Atr ) were measured, the
theoretical description of a comparable accuracy meets essential difficulties. For the astrophysical
applications, the challenging problems is a consistent description of the near-threshold 0+
2 (Hoyle)
state, whose properties are extremely sensitive to parameters in the α-cluster model. On the
other hand, the choice of the effective two-body and three-body potentials is of general interest
and their parameters have to be adjusted to fit the 12 C observables.
Previous calculations [5, 6] revealed that the α-cluster model, even with a simplest local
α-α potentials, provides a surprisingly good description of the ground and excited states of the
12
C nucleus. The aim of this reportis to present the calculations of the lowest 0+ states of 12 C
with the α-α potentials, which are chosen to describe the s-, d-, g-wave α-α elastic-scattering
phase shifts up to energy Ecm < 12 MeV and the experimental energy and width of the α-α
resonance (the ground state of 8 Be). The effective three-body potential of a Woods-Saxon form
is taken, which parameters are chosen to fix the ground and excited 0+ state energies and the
ground-state’s root-mean-square radius at their experimental values.
The main result is the amazing descriptive ability of the above-described α-cluster model.
The calculations reveal that for a number of the α-α potentials both the width of the Hoyle state
Γ and the structural parameters M12 and Atr are in excellent agreement with the experimental
data as shown in Fig. 1. There is enough room for further improvement of the model; it is
discussed that description of the electromagnetic and (α, α) reactions could be useful to impose
additional restrictions on the effective potentials.
Auteur principal
Prof.
Oleg O. I. Kartavtsev
(Dubna, Russia)
Co-auteurs
Dr
A.V. Makykh
(Dubna)
Prof.
Dmitri Fedorov
(Aarhus, DK)
