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REVIEW 4 major objections 5 minor 41 references

Gamow-Teller transition strengths for selected ${fp}$ shell nuclei

T0 review · 4 major / 5 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read The paper claims that shell-model calculations with KB3G and GXPF1A interactions in the fp model space reproduce the measured Gamow-Teller strength distributions for five transitions, matching individual peaks qualitatively and summed…

desk verdict A straightforward shell-model calculation with useful B(GT) distributions, but the abstract promises more agreement than the paper's own comparisons deliver. read the letter →

arxiv 1909.01609 v2 pith:T55MUKNG submitted 2019-09-04 nucl-th

Vikas Kumar , Praveen C. Srivastava , Anil Kumar This is my paper · ORCID
classification nucl-th PACS 21.60.Cs
keywords Gamow-TellerstrengthshellmodelfpeffectiveinteractionKB3GGXPF1Abetadecayquenchingfactor
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This paper aims to show that standard shell-model effective interactions can describe measured Gamow-Teller (GT) transition strengths in medium-mass nuclei. For five decays in the fp shell—44Sc→44Ca, 45Ti→45Sc, 48Ti→48V, 66Co→66Ni, and 66Fe→66Co—the authors compute B(GT) distributions using KB3G and GXPF1A interactions, and add a truncated fpg9/2 calculation with GXPF1Br+VMU for the two A=66 cases. They find that individual transition strengths match experiment qualitatively and that the summed B(GT) values closely reproduce the observed running sums. The calculated high-energy strengths, which experiments have not yet reached, are presented as predictions that future measurements could test. Because GT strengths feed electron-capture rate estimates in supernovae and neutron-star crusts, a reliable description of them matters for astrophysical modelling.

What carries the argument

The central object is the Gamow-Teller strength B(GT±), the squared, quenched matrix element of the one-body spin-isospin operator Σ_k σ^k τ^k_± between parent and daughter shell-model states. The machinery that carries the calculation is the shell-model effective Hamiltonian in the fp space, built from the KB3G and GXPF1A effective interactions, with GXPF1Br+VMU used for the fpg9/2 space (here with the d5/2 orbital removed and a fixed minimum occupation of f7/2 and a maximum of two g9/2 nucleons). These interactions supply the single-particle energies and two-body matrix elements whose diagonalization yields the initial and final state wave functions; summing the individual B(GT) values over final states up to a given excitation energy produces the running sums that the paper compares with experiment.

What would settle it

Repeat the 66Co→66Ni and 66Fe→66Co calculations in the full fpg9/2d5/2 space without the fixed occupation truncation; if the summed B(GT) strengths or the placement of the lowest 66Fe→66Co peak change materially, the truncation is not innocuous and the quoted agreement for A=66 is not robust.

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Extended reading notes

Core claim

The paper's central claim is that the measured Gamow-Teller strength distributions for these five fp-shell transitions are reproduced by shell-model calculations in the fp space, and that including the g9/2 orbital via a truncated fpg9/2 calculation does not overturn that agreement for the A=66 cases. The comparison is made through B(GT) = 1/(2Ji+1) $f_q^{2}$ |<f||Σ_k σ^k τ^k_±||i>|^2 with a quenching factor f_q = 0.66, applied to all results. For 44Sc→44Ca, 45Ti→45Sc, and 48Ti→48V the calculations use the full fp space; for 66Co→66Ni and 66Fe→66Co the fp-space results are supplemented by fpg9/2 results in which at most two neutrons and two protons occupy g9/2 and d5/2 is excluded. The paper states that qualitative agreement holds for the individual transitions and that the calculated summed strengths closely reproduce the observed ones, with GXPF1A typically matching the measured sums more closely than KB3G.

Load-bearing premise

The load-bearing premise is that the truncated model space for the A=66 nuclei—with six particles fixed in f7/2, at most two neutrons and two protons in g9/2, and d5/2 excluded—does not distort the computed Gamow-Teller strength distributions enough to change the conclusions; if it does, the claimed agreement for those transitions rests on an artifact.

Editorial extensions

If this is right

  • If the agreement holds, GXPF1A and KB3G in the fp space can serve as reliable inputs for electron-capture and beta-decay rate estimates in this mass region.
  • The predicted high-energy GT concentrations—around 10 MeV in 44Ca, 2–10 MeV in 45Sc, and 4–20 MeV in the A=66 nuclei—give concrete targets for future charge-exchange or decay experiments.
  • The 48Ti→48V results, where GXPF1A tracks the observed running sum better than KB3G, support using GXPF1A for nuclei near the upper end of the fp shell.
  • The A=66 fpg9/2 results, despite their truncation, provide a first estimate of how adding the g9/2 orbital shifts GT strength in these decays.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • A natural extension is to use the same calculated B(GT) distributions, not just their sums, as direct inputs for stellar electron-capture rate calculations on these nuclei; the paper stops at the strength comparison.
  • The uniform q=0.66 quenching across five transitions hints that a single quenching factor may suffice for fp-shell GT strengths, a hypothesis a broader survey across the shell could test.
  • If future measurements confirm the predicted high-energy strength, the truncated fpg9/2 results would motivate an untruncated fpg9/2d5/2 calculation to separate genuine g9/2 effects from truncation artifacts.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 5 minor

Summary. The paper reports shell-model calculations of Gamow-Teller transition strengths for five transitions in the fp shell: 44Sc→44Ca, 45Ti→45Sc, 48Ti→48V, 66Co→66Ni, and 66Fe→66Co. The authors use the KB3G and GXPF1A interactions in the full fp space, and for the two A=66 cases they additionally present results in the fpg9/2 space using the GXPF1Br+VMU interaction. The calculated B(GT) distributions and running sums are compared with beta-decay and charge-exchange data, with a global quenching factor q=0.66 applied. The paper's central claim, stated in the abstract and conclusion, is that qualitative agreement is obtained for the individual transitions while the calculated summed transition strengths closely reproduce the observed ones. The paper also emphasizes predictions of high-lying GT strength that could be tested by future experiments.

Significance. The study is useful as a systematic benchmark of standard shell-model interactions against newly measured or recently compiled GT strength distributions, and the high-energy predictions are potentially relevant for astrophysical electron-capture rates and future measurements. The paper uses published interactions and the widely used NuShellX@MSU code, and the comparison figures show visible similarities in the overall fragmentation patterns. However, the headline claim of qualitative agreement is substantially overstated relative to the paper's own account of missing and shifted transitions, and the fpg9/2 truncation for A=66 is not convergence tested. If the authors rework the central claim into a precise, per-transition statement, the shell-model results remain a useful addition to the literature; as written, the main conclusion is not adequately supported.

major comments (4)
  1. [Abstract, Sec. III C, Sec. IV] The central claim that 'qualitative agreement' holds for the individual transitions is not supported by the paper's own comparison for 48Ti→48V: Sec. III C states that the dominant observed GT strength at Ex=3.387 MeV is 'missing in both the calculations,' yet no energy tolerance, strength threshold, or treatment of experimental uncertainties is defined that would allow a reader to judge whether the remaining peaks constitute agreement. I request a transition-by-transition matching statistic (e.g., energy and strength residuals for matched peaks, missed-peak count) or a clearly qualified claim that explicitly reports the missing and shifted transitions.
  2. [Sec. III E, Sec. IV] For 66Fe→66Co, the text reports that the second dominant observed strength at 0.982 MeV is missing in all three calculations and that the GXPF1Br+VMU fpg9/2 calculation shifts the first strength to higher excitation energy. These failures are acknowledged in Sec. III E but are not reflected in the abstract/conclusion assertion that individual transitions are in qualitative agreement. The conclusion should be rewritten to state per-transition success/failure and to separate the fragmentation comparison from the peak-by-peak comparison.
  3. [Sec. II] The fpg9/2 calculations for A=66 use an ad hoc truncation: six particles are fixed in f7/2, at most two neutrons (and, by the text, the same for protons) occupy g9/2, and d5/2 is excluded even though GXPF1Br+VMU is designed for the fpg9/2d5/2 space. No convergence test with respect to these restrictions is presented. Since the conclusions about the importance of g9/2 and the A=66 agreement depend on this truncation, the authors should test at least one or two neighboring truncations (e.g., allowing more g9/2 particles or including d5/2) or justify the choice from the ground-state wave functions.
  4. [Eq. (2), Sec. II] The absolute scale of the calculated B(GT) is set by the globally fitted quenching factor q=0.66 taken from Ref. [29], the authors' own earlier work. This makes the 'closely reproduce the observed summed strengths' part of the claim partly inherited from the normalization rather than a free prediction; the summed-strength comparison should be presented both quenched and unquenched, or with a clear statement that only the fragmentation pattern is being tested by these data.
minor comments (5)
  1. [Abstract and Sec. I] 'Week interaction' should be 'weak interaction'.
  2. [Eq. (1)] There is a stray parenthesis in 'A† JT )' in the equation; this should be corrected.
  3. [Table I] The column headings are unclear: state explicitly that the listed numbers are the maximum excitation energies (in MeV) of the computed spectra and the experimental window, and define what 'Transitions (No.)' means.
  4. [References] Refs [13] and [35] refer to the same Ganioglu paper, and Refs [14] and [36] refer to the same Stryjczyk paper; duplicate entries should be consolidated.
  5. [Figs. 1–5] The comparison panels would be much easier to assess if experimental B(GT) uncertainties were displayed; no error bars are shown in any of the figures.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the shell-model calculation is an out-of-sample test; the global quenching factor q=0.66 is an external input from cited prior work, not a parameter fitted to the transitions whose strengths are being reported.

full rationale

The paper's derivation chain is a standard shell-model calculation: it diagonalizes the effective Hamiltonian (Eq. 1) with published interactions (KB3G, GXPF1A, GXPF1Br+VMU) and evaluates B(GT) via Eq. (2). The excitation-energy distributions and transition-by-transition fragmentation in Figs. 1-5 are outputs of the diagonalization and are not fitted to the experimental B(GT) data shown in those figures. The only potentially self-referential input is the quenching factor q=0.66, cited to the authors' own Ref. [29]. This is a global multiplicative renormalization of the GT operator: it sets the overall scale of the summed strengths, but it does not determine which states carry strength, their excitation energies, or the relative pattern among transitions. The central empirical claim of the abstract, 'qualitative agreement for the individual transitions,' rests on the unquenched fragmentation pattern rather than on q, and the summed-strength claim is explicitly qualified in Sec. IV: 'In the case of 48Ti -> 48V, 45Ti -> 45Sc, 66Co -> 66Ni and 66Fe -> 66Co transitions, theoretical strengths are larger than the experimental value.' No equation in the paper defines the input in terms of the output, and no fitted parameter is relabeled as a prediction here. There is a separate correctness concern, not a circularity one: Sec. III C reports that the observed dominated 48Ti strength at Ex = 3.387 MeV is 'missing in both the calculations,' and Sec. III E reports that the second observed 66Fe strength at 0.982 MeV is missing and that the GXPF1Br+VMU result shifts the first peak; no matching tolerance or criterion is defined. Those issues concern whether the qualitative-agreement claim is overstated, not whether the calculation reduces to its inputs. The shell-model Hamiltonians and the quenching factor are independent of the target data, so the derivation is self-contained for circularity purposes.

Assumptions & free parameters 3 free parameters · 5 assumptions · 0 invented entities

The central claim depends on one global quenching factor fitted by the same authors, three hand-chosen truncation parameters for the A=66 fpg9/2 calculations, and several standard shell-model assumptions about the validity of the effective interactions and the model spaces. No new physical entities are introduced.

free parameters (3)
  • Global quenching factor q = 0.66
    Applied to all B(GT) values via Eq. (2). Taken from the authors' earlier fit (Ref. [29]) to GT and M1 data in the fp shell, so the total strength normalization is inherited from a fit rather than derived.
  • Minimum f7/2 occupancy for A=66 fpg9/2 calculations = 6 particles
    Chosen by hand in Section II for 66Co and 66Fe; this truncation defines the model space for the g9/2 study and affects the resulting strength distributions.
  • Maximum g9/2 occupancy for A=66 fpg9/2 calculations = 2 neutrons, also applied to protons
    Chosen by hand in Section II; limits the model space for the fpg9/2 results and is not justified by convergence checks.
assumptions (5)
  • domain assumption The effective interactions KB3G, GXPF1A and GXPF1Br+VMU provide a valid description of fp and fpg9/2 shell nuclei.
    The paper adopts these published interactions without re-deriving them (Section II).
  • domain assumption The Gamow-Teller operator can be represented as in Eq. (2) with a universal spin-isospin operator and a single global quenching factor.
    Standard shell-model approximation; the quenching factor q=0.66 absorbs omitted many-body effects.
  • ad hoc to paper Excluding the d5/2 orbital from the fpg9/2d5/2 interaction space does not materially change the A=66 results.
    Section II states GXPF1Br+VMU is for fpg9/2d5/2 but protons and neutrons are not allowed to occupy d5/2; no comparison is made to validate this exclusion.
  • ad hoc to paper The chosen fpg9/2 truncation (minimum 6 particles in f7/2, maximum 2 neutrons in g9/2) is adequate for 66Co and 66Fe ground states and GT transitions.
    The truncation is imposed in Section II without convergence checks, and the number of eigenstates (300) is a computational cutoff.
  • domain assumption Experimental B(GT) values from Refs. [27], [28], [13], and [36] can be directly compared with shell-model values computed to much higher excitation energies.
    The comparison window in Figures 1-5 is limited by the experimental excitation range, while theory extends much higher; the paper assumes the low-energy part is representative.

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Pith. "Pith review of Gamow-Teller transition strengths for selected ${fp}$ shell nuclei." pith.science (2026). https://pith.science/paper/T55MUKNG

@misc{pith2026190901609,
  author       = {Pith},
  title        = {Pith review of: Gamow-Teller transition strengths for selected $fp$ shell nuclei},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/T55MUKNG}},
  note         = {Machine review of arXiv:1909.01609}
}
abstract

We have reported a systematic shell model description of the experimental Gamow-Teller transition strength for $^{44}$Sc $\rightarrow$ $^{44}$Ca, $^{45}$Ti $\rightarrow$ $^{45}$Sc, $^{48}$Ti $\rightarrow$ $^{48}$V, $^{66}$Co $\rightarrow$ $^{66}$Ni, and $^{66}$Fe $\rightarrow$ $^{66}$Co transitions using KB3G and GXPF1A interactions for $fp$ model space. In order to see the importance of higher orbital for $^{66}$Co $\rightarrow$ $^{66}$Ni and $^{66}$Fe $\rightarrow$ $^{66}$Co transitions, we have reported the shell model results with $fpg_{9/2}$ space using GXPF1Br+$V_{MU}$ interaction. We have obtained the qualitative agreement for the individual transitions, while the calculated summed transition strengths closely reproduce the observed ones.

Figures

Figures reproduced from arXiv: 1909.01609 by the authors.

Figure 1
Figure 1. FIG. 1: Comparison of experimental and theoretical [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. FIG. 2: Comparison of experimental and theoretical [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 4
Figure 4. FIG. 4: Comparison of experimental and theoretical [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figures from the paper (1 more)
Figure 5
Figure 5. Figure 5: FIG. 5: Comparison of experimental and theoretical [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]

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Reference graph

Works this paper leans on

41 extracted references · 38 canonical work pages

  1. [29]

    Caurier et al ., Nucl

    E. Caurier et al ., Nucl. Phys. A 653, 439 (1999). 8

    work page 1999

  2. [1]

    44Sc(2+) 44Ca(1+,2+,3+) 50 3.301 19.204 16.883 - [ 27]

    work page

  3. [2]

    45Ti( 7 2 − ) 45Sc( 5 2 − , 7 2 − , 9 2 − ) 50 1.662 10.022 9.384 - [ 28]

    work page

  4. [3]

    48Ti(0+) 48V(1+) 350 12.646 13.048 12.983 - [ 13]

    work page

  5. [4]

    66Co(1+) 66Ni(0+,1+,2+) 100 a 3.752 15.506 19.540 18.730 [ 14]

    work page

  6. [5]

    bFor GXPF1Br+ VM U interaction we have calculated 300 eigen values

    66Fe(0+) 66Co(1+) 100 b 2.236 13.546 17.880 13.638 [ 14] aFor GXPF1Br+ VM U interaction we have calculated 300 eigen values. bFor GXPF1Br+ VM U interaction we have calculated 300 eigen values. maximum 2 neutrons in the g9/ 2 orbital. Thus we put same truncations for both protons and neutrons. The shell model calculations are performed using the code NuShe...

    work page

  7. [6]

    It is possible to improve further GT strengths results by adding the effect of two-body currents (2BCs) in the quenching factor [ 30–33]

    66 [ 29]. It is possible to improve further GT strengths results by adding the effect of two-body currents (2BCs) in the quenching factor [ 30–33]. Recently for the ab initio cal- culations it was suggested that if we use evolve operator then there is no need to use quenching factor [ 34]. III. COMP ARISON OF THEORETICAL AND EXPERIMENTAL B(GT ) STRENGTH DI...

    work page 2019

  8. [7]

    Bohr and B

    A. Bohr and B. R. Mottelson, Nuclear Structure (Ben- jamin, New York, 1969), Vol. 1

    work page 1969

Show all 41 references
  1. [8]

    Suhonen, From Nucleons to Nucleus: Concepts of Mi- croscopic Nuclear Theory (Springer, Berlin, 2007)

    J. Suhonen, From Nucleons to Nucleus: Concepts of Mi- croscopic Nuclear Theory (Springer, Berlin, 2007)

    2007

  2. [9]

    Osterfeld, Rev

    F. Osterfeld, Rev. Mod. Phys. 64, 491 (1992)

    1992

  3. [10]

    Rubio and W

    B. Rubio and W. Gelletly, Lect. Notes Phys. 764, 99 (2009)

    2009

  4. [11]

    Fujita, B

    Y. Fujita, B. Rubio, and W. Gelletly, Prog. Part. Nucl. Phys. 66, 549 (2011)

    2011

  5. [12]

    M. N. Harakeh and A. van der Woude, Giant Resonances, Oxford Studies in Nuclear Physics (Oxford University Press, Oxford, 2001), Vol. 24, and references therein

    2001

  6. [13]

    R. A. Broglia and V. Zelevinsky (eds.), Fifty Years of Nuclear BCS, Pairing in Finite Systems (World Scientific, Singapore, 2013)

    2013

  7. [14]

    Fujita et al ., Phys

    Y. Fujita et al ., Phys. Rev. Lett. 112, 112502 (2014)

    2014

  8. [15]

    C. L. Bai et al ., Phys. Rev. C 90, 054335 (2014)

    2014

  9. [16]

    Sarriguren, A

    P. Sarriguren, A. Algora, and G. Kiss, Phys. Rev. C 98, 024311 (2018)

    2018

  10. [17]

    Saxena, P.C

    A. Saxena, P.C. Srivastava and T. Suzuki, Phys. Rev. C 97, 024310 (2018)

    2018

  11. [18]

    Kumar and P.C

    V. Kumar and P.C. Srivastava, Eur. Phys. J. A 52 , 181 (2016)

    2016

  12. [20]

    Stryjczyk et al ., Phys

    M. Stryjczyk et al ., Phys. Rev. C 98, 064326 (2018)

    2018

  13. [21]

    Harper and L

    M. Harper and L. Zamick, Phys. Rev. C 91, 014304 (2015)

    2015

  14. [22]

    Harper and L

    M. Harper and L. Zamick, Phys. Rev. C 91, 054310 (2015)

    2015

  15. [23]

    Talmi, Adv

    I. Talmi, Adv. Nucl. Phys. 27, 1 (2003)

    2003

  16. [24]

    Caurier, G

    E. Caurier, G. Mart ´ ınez-Pinedo, F. Nowacki, A. Poves, and A.P. Zuker, Rev. Mod. Phys. 77, 427 (2005)

    2005

  17. [25]

    Richtler, Nucl

    A. Richtler, Nucl. Phys. A 507, 99 (1990)

    1990

  18. [26]

    V.K.B. Kota, R. Sahu, K. Kar, J. M. G. G´ omez, and J. Retamosa, Phys. Rev. C 60, 051306(R) (1999)

    1999

  19. [27]

    Caurier, A

    E. Caurier, A. Poves, and A. P. Zuker, Phys. Rev. Lett. 74, 1517 (1995)

    1995

  20. [28]

    Marketin, G

    T. Marketin, G. Mart ´ ınez-Pinedo, N. Paar, and D. Vrete- nar, Phys. Rev. C 85, 054313 (2012)

    2012

  21. [30]

    Honma et al ., Eur

    M. Honma et al ., Eur. Phys. J. A 25, 499 (2005)

    2005

  22. [31]

    Togashi et al ., Phys

    T. Togashi et al ., Phys. Rev. C 91, 024320 (2015)

    2015

  23. [32]

    Brown, and W.D.M

    B.A. Brown, and W.D.M. Rae, The Shell-Model Code NuShellX@MSU, Nucl. Data Sheets 120, 115 (2014)

    2014

  24. [33]

    Singh, J

    Jun Chen, B. Singh, J. A. Cameron, Nuclear Data Sheets 112, 2357 (2011)

    2011

  25. [34]

    T. W. Burrows, Nuclear Data Sheets 109, 171 (2008)

    2008

  26. [35]

    Kumar, P.C

    V. Kumar, P.C. Srivastava and H. Li, J. Phys. G: Nucl. Part. Phys. 43, 105104 (2016)

    2016

  27. [36]

    Bender et al ., Phys

    M. Bender et al ., Phys. Rev. C 65, 054322 (2002)

    2002

  28. [37]

    T. R. Rodr ´ ıguez et al ., Phys. Rev. Lett. 105, 252503 (2010)

    2010

  29. [38]

    Men´ endezet al ., Phys

    J. Men´ endezet al ., Phys. Rev. Lett. 107, 062501 (2011)

    2011

  30. [39]

    Ekstrom et al ., Phys

    A. Ekstrom et al ., Phys. Rev. Lett. 113, 262504 (2014)

    2014

  31. [40]

    Gysbers et al ., Nat

    P. Gysbers et al ., Nat. Phys. 428, 428 (2019)

    2019

  32. [41]

    Ganioglu et al ., Phys

    E. Ganioglu et al ., Phys. Rev. C 93, 064326 (2016)

    2016

  33. [42]

    Stryjczyk, Y

    M. Stryjczyk, Y. Tsunoda, et al ., Phys. Rev. C 98, 064326 (2018)

    2018

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