REVIEW 2 major objections 6 minor 1 cited by
Polarization observables in semileptonic $V\to P$ decays of quarkonia
T0 review · 2 major / 6 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read Quarkonium weak decays get first polarization predictions
desk verdict Solid helicity-amplitude formalism with first CCQM predictions for quarkonia weak decays, but the numerical results lean on model form factors with a known 3σ tension with lattice. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The carrying object is the helicity-amplitude decomposition of the $V\to P\ell\bar{\nu}_\ell$ amplitude. The paper evaluates the hadronic tensor in the parent-meson rest frame and the leptonic tensor in the $W^*$ rest frame, contracting them through a helicity basis; the nonzero amplitudes are $H_{t0}$, $H_{\pm\mp}$, and $H_{00}$. The resulting normalized angular distribution is a tilted parabola in $\cos\theta$, $\tilde W(\theta)=a+b\cos\theta+c\cos^2\theta$, whose linear and quadratic coefficients map directly onto $A_{FB}$ and $C_F^\ell$, while $P_L^\ell$ follows from the helicity-flip and non-flip parts of the total rate.
What would settle it
Measure the $q^2$-dependent forward-backward asymmetry in $J/\psi\to D_{(s)}\ell\bar{\nu}_\ell$ at a charm-tau factory and compare the $q^2$ average with Table 3; a deviation larger than the quoted uncertainties would disprove either Eq. (20)'s angular structure or the input form factors. Alternatively, a lattice QCD computation of the $J/\psi\to D_s$ form factors that moves them by more than the model's error bars would directly falsify the numerical predictions, since Eq. (20) would still hold but the helicity amplitudes would change.
Extended reading notes
Core claim
The central claim is that the Standard Model effective Hamiltonian, written in terms of the helicity amplitudes $H_{t0}$, $H_{+-}$, $H_{-+}$, and $H_{00}$ of Eq. (18), produces the exact twofold differential decay rate of Eq. (20). From its angular coefficients the paper defines three observables, $A_{FB}$, $C_F^\ell$, and $P_L^\ell$, and, with the covariant confined quark model form factors, predicts their $q^2$ dependence and $q^2$ averages in Table 3. The paper presents these as the first predictions for the charmonium channels and as a model-dependent Standard Model baseline for the bottomonium ones; the tension with lattice QCD in one channel is reported but not resolved here.
Load-bearing premise
The numbers rest on quark-model hadronic transition form factors taken from the authors' earlier papers without being re-derived here; if those form factors are off—and the paper itself records roughly a $3\sigma$ disagreement with lattice QCD for $J/\psi\to D_s$—the predicted asymmetries and polarizations will move.
Editorial extensions
If this is right
- The $q^2$-differential and $q^2$-averaged values in Table 3 become testable Standard Model predictions once a charm-tau factory measures $J/\psi\to D_{(s)}\ell\bar{\nu}_\ell$ decays.
- The near $-1$ lepton polarization for the electron and muon modes, and its sizable deviation for the tau modes, gives a lepton-universality-style check within a single decay.
- Because Eq. (20) is form-factor independent in shape, any other hadronic model can insert its own form factors and produce competing angular predictions without rederiving the distribution.
- The reported difference in $\langle A_{FB}\rangle$ between this work and the earlier quark-model calculation means a precise measurement can discriminate between the competing transition form factors.
Reading between the lines
- The angular-distribution coefficients themselves, not just the three named observables, could be extracted as moments from future data and compared directly with the model's $\tilde W(\theta)$.
- If lattice QCD form factors for $J/\psi\to D_s$ become available and shift the covariant confined quark model ones by the suggested $3\sigma$, the forward-backward asymmetry is the observable most likely to move, since it depends on the interference term $H_{t0}H_{00}$.
- The same helicity machinery transfers to any vector-to-pseudoscalar semileptonic transition, such as $D^*\to D\ell\bar{\nu}_\ell$, for which no angular predictions exist yet.
- The lepton-mass effects enter through the helicity-flip factor $\delta_\ell$, so the $\tau$ modes of $\Upsilon(1S)\to B_{(c)}\ell\bar{\nu}_\ell$ are the most sensitive channels for testing that structure.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper derives a twofold angular decay distribution for semileptonic vector-to-pseudoscalar decays V → P ℓ ν̄ using the helicity amplitude method, and uses it to define and predict the forward-backward asymmetry, lepton-side convexity parameter, and final-lepton longitudinal polarization. The formalism is applied to J/ψ → D_(s) ℓ ν̄ and Υ(1S) → B_(c) ℓ ν̄, with hadronic form factors taken from earlier Covariant Confined Quark Model studies. The general distribution in Eq. (20) is form-factor independent; the numerical predictions in Table 3 are model-dependent and are compared with BSW and NRQCD results where available. The paper validates its helicity formalism by recovering the branching fractions obtained from the standard integration in Eq. (9).
Significance. If the numerical predictions are accepted, the paper provides a useful Standard Model baseline for rare semileptonic quarkonia decays that could be tested at BESIII and a future Super Charm-Tau factory. The central derivation is internally consistent: Eq. (21) follows from integrating Eq. (20), and Eqs. (25)-(27) agree with the coefficients of the normalized angular distribution in Eq. (24). The reproduction of the previously known branching fractions is a strong consistency check. The main weakness is the model dependence of Table 3: the CCQM form factors used for J/ψ → D_s are in about 3σ tension with the recent LQCD calculation in Ref. [18], and the paper does not quantify how this tension propagates into the predicted polarization observables.
major comments (2)
- [§3, Table 3 and Eq. (29)] The central numerical predictions in Table 3 inherit the CCQM form factors from Refs. [19,20] and are not cross-checked against an independent form-factor input for the J/ψ channels. Table 1 shows that the CCQM branching fraction for J/ψ → D_s e ν̄, 3.30(50)×10⁻¹⁰, is about 3σ above the LQCD result 1.90(8)×10⁻¹⁰ from Ref. [18]; the agreement is better for J/ψ → D but still not at the 1σ level. Because ⟨A_FB⟩, ⟨C_F^ℓ⟩, and ⟨P_L^ℓ⟩ are q²-weighted ratios of helicity amplitudes, this discrepancy can shift the observables beyond the quoted uncertainties, which reflect only CCQM parameter errors. I request that the authors either recompute the observables using the LQCD form factors of Ref. [18] (or another independent set), or quantify the sensitivity of Table 3 to the form-factor input, and state clearly in the abstract and summary that the numerical predictions are CCQM-model predictions rather than model-independent SM predictions.
- [§2, Eq. (3) and Refs. [19,20]] The form factors A0, A+, A−, and V are taken from previous work without providing their explicit q² parametrization or the fitted model parameters. This makes Table 3 and Figures 2–9 not independently reproducible; a reader cannot assess the propagation of uncertainties or test the sensitivity to the model. Please include the explicit form-factor functions (or a supplemental file) used in the numerical evaluation, together with the relevant CCQM parameter values.
minor comments (6)
- [General] There are typos throughout: 'seperate' and 'hierachies' in Section 1, 'upcomming' in Section 1, and 'devided' near Eq. (22).
- [Eq. (4)] Eq. (4) contains a duplicated trace identity; one of the two identical tr(γ5γμγνγαγβ) lines should be removed or corrected.
- [Eq. (20)] The first line of Eq. (20) has a prefactor 1/96 while the second line has 1/36; the relation W(θ) = (3/8){…} should be stated explicitly to avoid an apparent inconsistency.
- [Table 3] In the Table 3 caption, 'Res ults form Ref. [16]' should read 'Results from Ref. [16]'.
- [References] Reference [19] lists PRD 92 074030 (2015) with arXiv:1701.07377; please verify the arXiv number, as it appears to correspond to a 2017 submission, and correct it if needed.
- [Eq. (28)] Eq. (28) uses the notation '−−−→' instead of a proper arrow; please typeset it as a standard arrow.
Circularity Check
No significant circularity: the angular-distribution derivation is self-contained, and the numerical predictions use prior CCQM form factors as model input rather than as fits to the predicted observables.
full rationale
The central derivation of Eq. (20) is self-contained: the helicity amplitudes in Eq. (18) follow from the Lorentz decomposition in Eq. (3), the polarization vectors in Eq. (16), and the standard W*-frame leptonic tensor. The leptonic tensor in Eq. (19) is quoted from the authors' earlier Ref. [29], but it is a standard perturbative result, and the paper provides an internal cross-check: integrating Eq. (20) over cos(theta) gives Eq. (21), which reproduces the same branching fractions as Eq. (9) in Tables 1 and 2. The numerical predictions in Table 3 are functions of the CCQM form factors A0, A+, A-, and V taken from Refs. [19,20]; those form factors were fixed by other hadronic inputs in earlier work and are not fitted to the forward-backward asymmetry, convexity, or lepton polarization reported here. The paper itself notes the ~3-sigma tension with LQCD for J/psi -> D_s and ~2-sigma agreement for J/psi -> D, which indicates model uncertainty rather than circularity. Self-citations appear, but they are not used as a uniqueness theorem or as a substitute for an independent derivation of the central result, so the derivation chain is not circular.
Assumptions & free parameters
free parameters (1)
- CCQM parameters (constituent quark masses and infrared confinement cutoff) =
not quoted here; set in Refs [19,20]
assumptions (5)
- domain assumption The weak decay is governed by the Standard Model effective Hamiltonian of Eq. (1) with left-handed currents.
- standard math The V to P hadronic matrix element has the four-form-factor decomposition of Eq. (3).
- domain assumption The CCQM form factors from Refs [19,20] correctly describe the hadronic dynamics.
- standard math The helicity basis and completeness relations in Eqs. (12)-(13) hold.
- domain assumption Parent vector mesons are treated as narrow resonances when converting differential rates to branching fractions using total widths.
Cite this review
Pith. "Pith review of Polarization observables in semileptonic $V\to P$ decays of quarkonia." pith.science (2026). https://pith.science/paper/7EW6FUPE
@misc{pith2026250621902,
author = {Pith},
title = {Pith review of: Polarization observables in semileptonic $V\to P$ decays of quarkonia},
year = {2026},
howpublished = {\url{https://pith.science/paper/7EW6FUPE}},
note = {Machine review of arXiv:2506.21902}
}
abstract
We investigate the weak semileptonic decays of the charmonium $J/\psi$ and bottomonium $\Upsilon(1S)$ into a pseudoscalar meson, namely, the $J/\psi\to D_{(s)}\ell\bar{\nu}_\ell$ and $\Upsilon(1S)\to B_{(c)}\ell\bar{\nu}_\ell$ decays. We focus on the polarization observables including the forward-backward asymmetry, final lepton polarization, and lepton-side convexity parameter. In order to define these quantities, we apply the helicity amplitude method and obtain a twofold angular decay distribution for a general $V\to P\ell\bar{\nu}_\ell$ case. The hadronic form factors are taken from our previous work, where they were calculated in the Covariant Confined Quark Model. We provide theoretical predictions for the polarization observables and compare them with the literature.
Figures
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Forward citations
Cited by 1 Pith paper
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Reference graph
Works this paper leans on
-
[18]
First lattice QCD calculation of $J/\psi$ semileptonic decay containing $D$ and $D_s$ particles
Meng Y, Dang J L, Liu C et al. , First lattice QCD calculation of J/ψ semileptonic decay containing D and Ds particles, Phys. Rev. D 110 074510 (2024) [arXiv:2407.13568]
work page Pith review arXiv 2024
-
[1]
(Particle Data Group), Review of particle physics, Phys
Navas S et al. (Particle Data Group), Review of particle physics, Phys. Rev. D 110 030001 (2024)
work page 2024
-
[2]
(E598), Experimental Observation of a Heavy Particle J, Phys
Aubert J J et al. (E598), Experimental Observation of a Heavy Particle J, Phys. Rev. Lett. 33 1404 (1974)
work page 1974
-
[3]
(SLAC-SP-017), Discovery of a Narrow Resonance in e+e− Annihilation, Phys
Augustin J E et al. (SLAC-SP-017), Discovery of a Narrow Resonance in e+e− Annihilation, Phys. Rev. Lett. 33 1406 (1974)
work page 1974
-
[4]
Bodwin G T, Braaten E and Lepage G P, Rigorous QCD analysis of inclu sive annihilation and production of heavy quarkonium, Phys. Rev. D 51 1125 (1995) [arXiv:hep-ph/9407339]
arXiv 1995
-
[5]
Brambilla N, Pineda A, Soto J and Vairo A, Effective Field Theories for Heavy Quarkonium, Rev. Mod. Phys. 77 1423 (2005) [arXiv:hep-ph/0410047]
arXiv 2005
-
[6]
Besson D et al. (CLEO), Measurement of the direct photon momentum spectrum in Υ(1S), Υ(2S), and Υ(3S) decays, Phys. Rev. D 74 012003 (2006) [arXiv:hep-ex/0512061]
work page Pith review arXiv 2006
-
[7]
Ablikim M et al. (BESIII), Search for the rare semileptonic decay J/ψ →D−e+νe +c.c., JHEP 06 157 (2021) [arXiv:2104.06628]
Show all 29 references
-
[8]
(BESIII), Search for the semi-muonic charmonium decay J/ψ → D−µ+νµ +c.c., JHEP 01 126 (2024) [arXiv:2307.02165]
Ablikim M et al. (BESIII), Search for the semi-muonic charmonium decay J/ψ → D−µ+νµ +c.c., JHEP 01 126 (2024) [arXiv:2307.02165]
2024
-
[9]
, Experiments at the Super Charm-Tau factory, Phys
Achasov M N et al. , Experiments at the Super Charm-Tau factory, Phys. Usp. 67 55 (2024)
2024
-
[10]
Sanchis-Lozano M A, On the search for weak decays of heavy q uarkonium in dedicated heavy quark factories, Z. Phys. C 62 271 (1994)
1994
-
[11]
Kurdadze L M and Silagadze Z K, On some rare weak decays of vec tor mesons, Phys. Atom. Nucl. 63 882 (2000) [arXiv:hep-ph/9712430]
2000 arXiv
-
[12]
High Energy Phys
Dhir R, Verma R C and Sharma A, Effects of Flavor Dependence on Weak Decays of J/ψ and Υ, Adv. High Energy Phys. 706543 (2013) [arXiv:0903.1201]
2013 arXiv
-
[13]
Shen Y L and Wang Y M, J/ψ weak decays in the covariant light-front quark model, Phys. Rev. D 78 074012 (2008)
2008
-
[14]
Chang Q, Wang L T and Li X N, Form factors of V ′ →V ′′ transition within the light-front quark models, JHEP 12 102 (2019) [arXiv:1908.04677]
2019 arXiv
-
[15]
Wang T, Jiang Y, Yuan H, Chai K and Wang G L, Weak decays of J/ψ and Υ(1S), J. Phys. G 44 045004 (2017) [arXiv:1604.03298]
2017 arXiv
-
[16]
Chang Q, Zhu J, Wang X L, Sun J F and Yang Y L, Study of semilepto nic Υ(nS) → Bcℓ¯νℓ weak decays, J. Phys. G 44 015001 (2017)
2017
-
[17]
Wang Y M, Zou H, Wei Z T, Li X Q and L¨ u C D, The Transition form fa ctors for semileptonic weak decays of J/ψ in QCD sum rules, Eur. Phys. J. C 54 107 (2008) [arXiv:0707.1138]
2008 arXiv
-
[19]
Ivanov M A and Tran C T, Exclusive decays J/ψ → D(∗)− (s) ℓ+νℓ in a covariant constituent quark model with infrared confinement, Phys. Rev. D 92 074030 (2015) [arXiv:1701.07377]
2015 arXiv
-
[20]
Tran C T, Ivanov M A, Santorelli P and Tran H C, Study of the sem ileptonic decays Υ(1S) →B(c)ℓ¯νℓ, Chin. Phys. C 49 013111 (2025) [arXiv:2408.13776]
2025 arXiv
-
[21]
Sheng J H, Zhou F Z, Li Y Y and Xu Y G Investigating the role of new physics in semileptonic Υ(nS) →Bcl−¯νl weak decays, Eur. Phys. J. C 85, 345 (2025)
2025
-
[22]
Branz T, Faessler A, Gutsche T Ivanov M A, K¨ orner J G and Lyu bovitskij V E, Relativistic con- stituent quark model with infrared confinement, Phys. Rev. D 81, 034010 (2010) [arXiv:0912.3710]
2010 arXiv
-
[23]
Ivanov M A, K¨ orner J G, Kovalenko S G, Santorelli P and Saidullae va G G, Form factors for semilep- tonic, nonleptonic and rare B (Bs) meson decays, Phys. Rev. D 85 034004 (2012) [arXiv:1112.3536]
2012 arXiv
-
[24]
Tran C T, Ivanov M A, Santorelli P and Vo Q C, Radiative decays D∗ (s) → D(s)γ in covariant confined quark model, Chin. Phys. C 48 023103 (2024) [arXiv:2311.15248]
2024 arXiv
-
[25]
, Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays, Phys
Groote S, Ivanov M A, K¨ orner J G et al. , Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays, Phys. Rev. D 103 093001 (2021) [arXiv:2102.12818]
2021 arXiv
-
[26]
Ivanov M A, K¨ orner J G, Santorelli P and Tran C T, D∗ Polarization as an Additional Constraint on New Physics in the b →cτ ¯ντ Transition, Particles 3 (1) 193 (2020) [arXiv:2009.00306]
2020 arXiv
-
[27]
K¨ orner J G and Schuler G A, Lepton Mass Effects in Semileptonic B Meson Decays, Phys. Lett. B 231 306 (1989)
1989
-
[28]
Faessler A, Gutsche T, Ivanov M A, K¨ orner J G and Lyubovitsk ij V E, The Exclusive rare decays B → K(K ∗)¯ℓℓ and Bc → D(D∗)¯ℓℓ in a relativistic quark model, Eur. Phys. J. direct 4 18 (2002) [arXiv:hep-ph/0205287]
2002 arXiv
-
[29]
, Exclusive semileptonic decays of D and Ds mesons in the covariant confining quark model, Front
Ivanov M A, K¨ orner JG, Pandya J N et al. , Exclusive semileptonic decays of D and Ds mesons in the covariant confining quark model, Front. Phys. (Beijing) 14 64401 (2019) [arXiv:1904.07740]
2019 arXiv
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