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arxiv: 2605.21218 · v1 · pith:K2GHADBGnew · submitted 2026-05-20 · ⚛️ nucl-th

The quenching of the axial-vector coupling constant g_A in β-decay: joint effects from chiral two-body currents and many-body correlations

Bin-Lei Wang , Wan-Li Lv , Li-Gang Cao , Yi-Fei Niu , Gianluca Colo , Hiroyuki Sagawa , Feng-Shou Zhang This is my paper

Pith reviewed 2026-05-21 01:29 UTC · model grok-4.3

classification ⚛️ nucl-th
keywords beta decayGamow-Teller transitionsaxial-vector couplingquenching factorchiral effective field theorytwo-body currentsparticle-vibration couplingrandom phase approximation
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The pith

Combining particle-vibration coupling with chiral two-body currents quenches the Gamow-Teller strength in beta decay to match experiment without extra parameters.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines why the axial-vector coupling constant g_A must usually be reduced by about 25 percent in nuclear beta-decay calculations to match observed Gamow-Teller strengths. It develops a microscopic method that adds many-body correlations through particle-vibration coupling on top of random phase approximation calculations and then folds in contributions from two-body currents taken from chiral effective field theory. When both pieces are evaluated together in three closed-shell nuclei using Skyrme functionals, the resulting Gamow-Teller matrix elements agree with data and produce quenching factors between roughly 0.73 and 0.80. This range sits close to the long-used empirical value of 0.75 and emerges without any manual adjustment of parameters.

Core claim

Self-consistent RPA plus particle-vibration coupling calculations performed with several Skyrme energy density functionals in 56Ni, 100Sn and 132Sn, followed by evaluation of chiral two-body current matrix elements on the obtained wave functions, produce a joint quenching of Gamow-Teller strength that reproduces experimental values quantitatively. The extracted quenching factors q lie in the interval approximately 0.73 to 0.80.

What carries the argument

Joint action of particle-vibration coupling correlations and matrix elements of chiral two-body currents evaluated on RPA wave functions.

If this is right

  • Gamow-Teller strengths in the three closed-shell nuclei match experiment once both particle-vibration coupling and two-body currents are included.
  • The derived quenching factors remain between 0.73 and 0.80 across different Skyrme functionals and lie near the standard phenomenological value 0.75.
  • Neither particle-vibration coupling nor two-body currents alone suffices for quantitative agreement with data.
  • The same framework can be applied to other doubly magic nuclei without introducing new adjustable parameters.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The approach may supply quenching factors for beta-decay rate calculations in nuclei away from closed shells once open-shell extensions become available.
  • Similar joint treatment of correlations and two-body currents could improve theoretical inputs for beta-decay processes that set the timescale of stellar nucleosynthesis.
  • Direct comparison of the same wave functions against other electroweak observables would test whether the extracted quenching is universal or transition-specific.

Load-bearing premise

The many-body wave functions obtained from self-consistent RPA plus particle-vibration coupling with Skyrme functionals are accurate enough to compute the matrix elements of the chiral two-body currents.

What would settle it

A side-by-side calculation of Gamow-Teller strengths in one of the three nuclei with and without the chiral two-body current terms, checking whether only the combined result falls inside the observed experimental range.

Figures

Figures reproduced from arXiv: 2605.21218 by Bin-Lei Wang, Feng-Shou Zhang, Gianluca Colo, Hiroyuki Sagawa, Li-Gang Cao, Wan-Li Lv, Yi-Fei Niu.

Figure 1
Figure 1. Figure 1: FIG. 1: (Color online). Theoretical and experimental B(GT) distributions in the daughter nuclei of [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: (Color online). Ratios of theoretical to experimental B(GT) [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: (Color online). Comparison of the calculated B(GT) in [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4: (Color online). Evolution of the B(GT) in [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 1
Figure 1. Figure 1: FIG. 1: (Color online). The convergence of the calculated B(GT) for [PITH_FULL_IMAGE:figures/full_fig_p011_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: (Color online). B(GT) values in [PITH_FULL_IMAGE:figures/full_fig_p011_2.png] view at source ↗
read the original abstract

In nuclear $\beta$-decay calculations, the axial-vector coupling constant $g_A \approx 1.27$ usually needs to be quenched phenomenologically by a factor $q~\approx$ 0.75 to reproduce {the Gamow-Teller (GT) transition strengths}. We propose a novel approach to quench the GT {strength} of $\beta$-decay within the microscopic random phase approximation (RPA) plus particle-vibration coupling (PVC) approach, incorporating the contributions of two-body currents (TBC) derived from chiral effective field theory ($\chi$EFT). Self-consistent RPA+PVC calculations are performed in three doubly magic nuclei, $^{56}$Ni, $^{100}$Sn, and $^{132}$Sn, with various Skyrme energy density functionals, and the effect of TBC is evaluated by using the obtained many-body wavefunctions. A combined effects of the many-body correlations introduced by PVC and chiral TBC quench the GT strength and reproduce quantitatively experimental data without any additional adjustments. The extracted quenching factors $q$ by the present microscopic model lie in the range $\approx$ 0.73--0.80, which is quite close to the commonly adopted empirical value of $q \approx 0.75$.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper claims that a microscopic RPA+PVC approach with Skyrme energy density functionals, when combined with chiral EFT two-body currents evaluated on the resulting many-body wavefunctions, quenches Gamow-Teller strengths in three doubly magic nuclei (56Ni, 100Sn, 132Sn) to reproduce experimental data quantitatively. No additional phenomenological adjustments are made, and the extracted quenching factors lie in the range q ≈ 0.73–0.80, close to the empirical value of 0.75.

Significance. If the central result holds, the work provides a notable microscopic explanation for g_A quenching by demonstrating a joint cancellation between PVC-induced many-body correlations and chiral TBC contributions. This is a strength: the model avoids ad-hoc quenching parameters and uses only Skyrme EDFs plus chiral currents, offering a path toward more predictive beta-decay calculations in exotic nuclei.

major comments (2)
  1. The load-bearing assumption that self-consistent RPA+PVC wavefunctions generated with phenomenological Skyrme EDFs are sufficiently accurate for evaluating chiral TBC matrix elements is not cross-validated. The manuscript reports no stability tests against alternate Skyrme parametrizations, variations in the PVC phonon space, or comparisons to ab-initio wavefunctions for the same nuclei; if this premise fails, the reported quantitative agreement (q ≈ 0.73–0.80) could reflect an inconsistent many-body basis rather than genuine microscopic cancellation.
  2. The abstract states quantitative agreement with data and gives the q range, yet the provided information contains no explicit comparison tables, convergence studies, or error estimates for the GT strengths. This absence prevents full verification of the central claim that the combined PVC+TBC effects reproduce experiment without adjustments.
minor comments (2)
  1. Clarify the precise implementation of the chiral TBC operators within the RPA+PVC framework and how the matrix elements are computed on the correlated wavefunctions.
  2. Specify which Skyrme functionals were employed and whether results are shown for more than one parametrization.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major point below, indicating where revisions have been made to strengthen the presentation and validation of our results.

read point-by-point responses

  1. Referee: The load-bearing assumption that self-consistent RPA+PVC wavefunctions generated with phenomenological Skyrme EDFs are sufficiently accurate for evaluating chiral TBC matrix elements is not cross-validated. The manuscript reports no stability tests against alternate Skyrme parametrizations, variations in the PVC phonon space, or comparisons to ab-initio wavefunctions for the same nuclei; if this premise fails, the reported quantitative agreement (q ≈ 0.73–0.80) could reflect an inconsistent many-body basis rather than genuine microscopic cancellation.

    Authors: We acknowledge the importance of demonstrating robustness of the many-body wavefunctions used to evaluate the chiral TBC matrix elements. The manuscript already performs calculations with various Skyrme EDFs, producing quenching factors consistently in the 0.73–0.80 range. To address the concern, we have added explicit tests with two additional parametrizations and variations in the PVC phonon energy cutoff; the resulting GT strengths vary by at most 8% and the extracted q values remain within the quoted interval. Systematic comparisons to ab-initio wavefunctions for 100Sn and 132Sn are not included, as such calculations with sufficient accuracy for GT transitions are not currently available. revision: partial

  2. Referee: The abstract states quantitative agreement with data and gives the q range, yet the provided information contains no explicit comparison tables, convergence studies, or error estimates for the GT strengths. This absence prevents full verification of the central claim that the combined PVC+TBC effects reproduce experiment without adjustments.

    Authors: We agree that explicit tables, convergence checks, and error estimates would improve verifiability. In the revised manuscript we have inserted a new table that directly compares the calculated GT strengths (with and without PVC and TBC) to experimental data for all three nuclei. We have also added a dedicated subsection discussing convergence with respect to the RPA model space and the number of included phonons, together with uncertainty estimates obtained from these variations. revision: yes

standing simulated objections not resolved
  • Direct comparisons to ab-initio wavefunctions for 100Sn and 132Sn

Circularity Check

0 steps flagged

No significant circularity; derivation is self-contained numerical evaluation

full rationale

The paper computes GT quenching as the output of RPA+PVC wavefunctions (generated from standard Skyrme EDFs) combined with chiral TBC matrix elements evaluated on those wavefunctions. The extracted q range (0.73-0.80) is presented as a derived result that matches experiment without further parameter adjustment. No step reduces by construction to the target data, no fitted input is relabeled as prediction, and no self-citation or ansatz chain is invoked to force the central claim. The approach stands or falls on the physical accuracy of the inputs and approximations rather than tautological redefinition.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The calculation rests on standard nuclear many-body assumptions and chiral EFT inputs; the only free parameters are those already present in the chosen Skyrme functionals from earlier work.

free parameters (1)
  • Skyrme EDF parameters
    Various Skyrme energy density functionals are employed; their parameters were fitted to nuclear ground-state data in prior literature.
axioms (2)
  • domain assumption Chiral effective field theory supplies reliable two-body current operators for use inside correlated nuclear wave functions
    TBC contributions are evaluated using the RPA+PVC wave functions obtained with Skyrme functionals.
  • domain assumption RPA+PVC provides a sufficient description of many-body correlations in the chosen doubly magic nuclei
    Self-consistent calculations are performed in 56Ni, 100Sn, and 132Sn.

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