SciPost Submission Page

A time-dependent Hartree-Fock study of triple-alpha dynamics

by P. D. Stevenson, J. L. Willerton

Submission summary

As Contributors: Paul Stevenson
Arxiv Link: https://arxiv.org/abs/1909.01924v2
Date submitted: 2019-10-07
Submitted by: Stevenson, Paul
Submitted to: SciPost Physics Proceedings
Proceedings issue: 24th European Few Body Conference (University of Surrey, U.K.)
Domain(s): Theor. & Comp.
Subject area: Nuclear Physics - Theory

Abstract

Time-dependent Hartree-Fock calculations have been performed for fusion reactions of He-4 + He-4 -> Be*-8, followed by He-4 + Be*-8 . Depending on the orientation of the initial state, a linear chain vibrational state or a triangular vibration is found in 12C, with transitions between these states observed. The vibrations of the linear chain state and the triangular state occur at ~9 and 4 MeV respectively.

Current status:
Editor-in-charge assigned

Author comments upon resubmission

We thank the referee for the comments.

Yes, the paper is an intermediate step, though we hope the results as
presented are interesting in themselves. They reflect what was
presetned at the conference for which the paper is intended as a
proceeding article (which also has a 6 page limit, as a poster
contribution). I agree with the stated weakness that more variation
of the input parameters is needed to give a clearer picture of the
validity of this approach

In answer to the particlar points in the report

1) We included a sentence about the calculated (17.67 MeV) vs
experimental (28.30) binding energy of He-4 at the beginning of the
"Results" section. This serious underbinding is commented on in the
same section - that it may be expected to have qualitative effects on
the results, but that we wish to start from a known interaction to
give a starting point for the study

2) 2 MeV was chosen as being just above the Coulomb barrier which is
between 1 and 2 MeV (since 1 MeV is too low to fuse, we found) and we
are interested in low-energy behaviour. For much higher energy
qualitatively different dynamics would be expected -
e.g. fusion-fission. I'd expect the resonances that we saw to be
governed more by the properties of the force; with the oscillations'
frequencies governed by a restoring force that does not depend too
much on entrance channel behaviour except to the extent of how many
cycles the oscillation can happen. This is of course speculation
until more calculations are performed and analysed, which await future
work. In section 3.2 I have expanded the second paragraph which
previously stopped at the sentence "The centre of mass collision
energy is fixed at E_cm=2.0 MeV" to give a motivation for this
energy. I note that the similar previous study by Umar et al. (our
[4]) used 2.0 MeV as the collision energy, by coincidence (our value
was not chosen because they used it, but for the motivation mentioned
above)

3) Agreed. Ultimately we see this work as a stepping stone to
something like a time-dependent generator coordinate method (with time
as the generator coordinate) from which a spectrum with good angular
momentum could be generated from projected and mixed Slater
Determinants. The referee's suggestion of using the approximate
relation between impact parameter and spin would be a computationally
cheap way of getting an idea of the spin, and we'll look at this
suggestion for the followup work. An extra paragraph has been added
to section 3.2 at the end of the section to discuss obtaining spins.

4) Sorry. Numerous typos changed, and run through a spell checker.

Other changes:
* changed the postcode in my affiliation which I had typed incorrectly

* in the conlcusions I have been more explicit about which parameters
deserve further study, in line with the referee's comments.

List of changes

changes all detailed in the "author comments" field

Submission & Refereeing History

Resubmission 1909.01924v2 on 7 October 2019
Submission 1909.01924v1 on 5 September 2019

Reports on this Submission

Anonymous Report 1 on 2019-10-14 Invited Report

Strengths

The article present novel aspects related to the formation of carbon from triple alpha process

Report

The authors have accounted for all the recommendations I asked for in my previous report. For this reason, I recommend the article for publication.

  • validity: good
  • significance: good
  • originality: good
  • clarity: ok
  • formatting: good
  • grammar: good

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