REVIEW 1 major objections 4 minor 2 cited by
Higher partial waves in femtoscopy
T0 review · 1 major / 4 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read One term, the backward scattering amplitude, captures all partial-wave corrections to the femtoscopic correlation function.
desk verdict Useful and mostly right; the compact backward-amplitude formula (Eq. 26) is the real new result, but Eq. (20) as printed has a sign/constant error that breaks the printed derivation of Eq. (22) — fix that and this is a solid contribution. 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 central object is the partial-wave expansion of the two-body scattering wave function, $\varphi_q(r,\theta)=\sum_l (2l+1)i^l R_l(r)P_l(\cos\theta)$, used inside the Koonin–Pratt integral. The argument proceeds by (i) decomposing the correlation function into per-partial-wave corrections $\Delta C_l(q) = (2l+1)\int dr\,4\pi r^2 S(r)(|R_l(r)|^2-|j_l(qr)|^2)$; (ii) replacing each $R_l$ by its $O(1/r)$ asymptotic form in the region where both potential and centrifugal terms are negligible; (iii) using probability conservation to eliminate the $|f_l|^2$ terms; and (iv) summing the phases $(-1)^l=P_l(-1)$ to recognize the backward scattering amplitude. The Fourier–Laplace transform $\hat{S}(-2iq)=\int_0^\infty dr\,S(r)e^{2iqr}$ carries the source-size dependence and is what makes the compact formula possible.
What would settle it
Calculate the spherical-source correlation function exactly for a potential with a known higher-partial-wave resonance, such as a square well tuned so a p- or d-wave resonance sits near the relevant $q$, and compare the result with Eq. (26); if the difference exceeds the expected $O(1/r^2)$ asymptotic corrections over the source's support, the compact formula is refuted.
Extended reading notes
Core claim
The paper's central claim is Eq. (26): under the Koonin–Pratt assumptions with a spherical source, the correlation function is $C(q) = 1 + \frac{4\pi}{q}\operatorname{Im}[f(q,\theta=\pi)\,\hat{S}(-2iq)]$, where $f(q,\theta=\pi)$ is the backward scattering amplitude and $\hat{S}(-2iq)$ is the Fourier–Laplace transform of the radial source function. This formula encodes the summed contribution of every partial wave to the correction of the correlation function: expanding $f$ in partial waves turns it into $\sum_l (2l+1)(-1)^l \operatorname{Im}[f_l(q)\hat{S}(-2iq)]$. The traditional Lednicky–Lyuboshitz formula for the s wave follows as the $l=0$ special case, with two of its three terms combined through the optical theorem. The paper also establishes that the asymptotic-wave-function approximation underlying this generalized LL formula is not reliable for $l\ge 1$: the replacement of the true wave function by its $O(1/r)$ asymptotic form misses the $r^l$ centrifugal suppression near the origin, producing even the wrong sign for odd partial waves.
Load-bearing premise
The entire analysis assumes the Koonin–Pratt formula with the smoothness approximation that the relative momentum at emission equals the final relative momentum; if that equality fails for momenta up to 400 MeV, the corrected correlation function will not describe the measured one.
Editorial extensions
If this is right
- Higher partial waves are not negligible in general: their corrections scale as $q^{2l}$ at small $q$ but can dominate the s-wave correction at larger $q$, particularly when a higher-partial-wave resonance sits near the real axis.
- Equation (26) gives an explicit, closed-form way to compute the full partial-wave correction whenever the asymptotic wave-function approximation is valid, reducing the problem to knowing the backward amplitude and the source transform.
- The failure of the generalized LL formula for $l\ge 1$ means that standard analyses that add a Breit–Wigner resonance on top of an s-wave LL baseline are not justified by the LL framework; the centrifugal barrier must be built into the reference wave function.
- The same asymptotic plane-wave structure that yields the optical theorem yields the correlation formula, so the backward amplitude plays the role for correlations that the forward amplitude plays for the total cross section.
Reading between the lines
- A natural testable extension is to invert Eq. (26): with a measured $C(q)$ and an independently known source, one could extract $f(q,\pi)$ at momenta beyond those accessible in scattering experiments.
- The per-partial-wave power counting $\Delta C_l \sim q^{2l}$ implies that at sufficiently small $q$ the s wave always dominates, so any reported deviation from the s-wave LL formula at very low $q$ would signal a breakdown of the KP assumptions rather than higher-wave physics.
- The same asymptotic-plane-wave derivation could be repeated for non-spherical sources; the paper notes that then different partial waves interfere, so the simple sum over $l$ would be replaced by a sum over $l,l'$ and the backward-amplitude formula would acquire angular structure.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper extends the Koonin–Pratt and Lednický–Lyuboshitz femtoscopy formulae to higher partial waves. With a spherical source, the authors expand the relative wave function in partial waves and express the correlation function as a sum over l of Delta C_l involving |R_l|^2 - |j_l|^2 (Eqs. 15 and 16). They then approximate the radial functions by their O(1/r) asymptotic forms and obtain a generalized LL formula, Eq. (22), whose l-sum is resummed into the compact backward-amplitude formula Eq. (26). For a square-well potential, they show that higher-partial-wave contributions can dominate near resonances and that the generalized LL formula reproduces the s-wave LL result but fails quantitatively for l >= 1. The paper also clarifies the formal connection between the LL formula and the optical theorem via the forward/backward delta-function structure of the plane wave.
Significance. The exact partial-wave decomposition of the spherical-source KP formula is a simple and useful result for the femtoscopy community, which is increasingly encountering p- and d-wave resonances in data. The compact form Eq. (26) is elegant, and the reduction to the original s-wave LL formula is a valuable check. The explicit numerical comparison showing that the naive all-wave LL generalization fails for l >= 1 is an important caution for analyses. The paper is self-contained and the main derivations are explicit. However, the derivation of Eq. (22) in Sec. 3.2 contains a substantive algebraic error that makes the printed argument invalid, even though the final formula is correct and independently supported by Sec. 3.3.
major comments (1)
- [Sec. 3.2, Eq. (20)] The printed Eq. (20) is inconsistent with Eq. (19). Substituting Eq. (19) into Eq. (13) gives |R_l^III(r)|^2 = (1/(q^2 r^2)) [1/2 + (-1)^{l+1} Re{ (1/2 + i q f_l) e^{2iqr} }], so the integrand bracket in Eq. (20) should be 1/2 + (-1)^{l+1} Re[...], not 1 - (-1)^{l+1} Re[...]. The text's statement that the plane-wave case of Eq. (20) 'becomes unity' is false: with the printed bracket the l-sum diverges, and with the corrected bracket the asymptotic plane-wave partial-wave sum is still divergent. Consequently, the derivation of Eq. (22) by subtracting the plane-wave case of Eq. (20) is not valid as written. The final Eq. (22) is nevertheless correct: a direct recomputation yields it, and Sec. 3.3 gives an independent derivation of Eq. (26). The derivation in Sec. 3.2 must be corrected or replaced.
minor comments (4)
- [Sec. 2, after Eq. (6)] The phrase 's-save' should read 's-wave'.
- [Sec. 3.2] The word 'plain-wave' appears twice and should be 'plane-wave'.
- [Fig. 2 caption] The caption says 'The same as Fig. 2 but with deeper potentials'; it should refer to Fig. 1.
- [Sec. 3.3, Eq. (32)] The replacement of |B|^2 + |C|^2 by 2|C|^2 is justified only after integrating over angles and using probability conservation; this should be stated explicitly, since the equality is not pointwise.
Circularity Check
No circularity: the central results are derived from the externally stated Koonin–Pratt formula, with no fitted parameters and no load-bearing self-citation.
full rationale
The paper's starting point is the Koonin–Pratt formula, Eq. (2), which is presented as an external input from the literature (refs. [22,23]), not as a consequence of the paper's own results. The partial-wave generalization in Eqs. (15)–(16) follows directly by substituting the partial-wave expansion (11) into Eq. (2) and using Legendre orthogonality; this is a self-contained algebraic derivation. The generalized Lednický–Lyuboshitz formula, Eq. (22), is obtained from the asymptotic form R_III_l in Eq. (19), combined with probability conservation expressed in Eq. (21); neither of these inputs is derived from the target correlation formula. The compact backward-amplitude representation, Eq. (26), is obtained by explicitly summing the partial-wave series using the Legendre-polynomial identity (-1)^l = P_l(-1), which is again a self-contained step, and Sec. 3.3 independently re-derives both the optical theorem and the generalized LL formula from a common asymptotic plane-wave decomposition. The reproduction of the original s-wave LL formula in Sec. 3.2 is presented as a check against an external benchmark, not as an input: the coefficient matching in Eq. (25) verifies the generalized formula by comparing with the known Gaussian-source Fourier–Laplace transform. No parameter is fitted to any data; the square-well depths are illustrative model inputs. The paper also explicitly reports that the generalized LL formula fails for l >= 1, which is a self-correcting finding, not a circular vindication. Even if the printed Eq. (20) contains an algebraic sign-typo of the kind noted in the skeptical review, that is a correctness/proof defect rather than circularity, because the final compact formula is independently derived in Sec. 3.3. No step reduces a predicted quantity to an input by construction, and no load-bearing claim rests on a self-citation chain.
Assumptions & free parameters
free parameters (4)
- V0 (square well depth) =
50, 100, 300, 600 MeV
- b (square well width) =
1 fm
- mu (reduced mass) =
600 MeV
- R (Gaussian source size) =
2, 3, 4 fm
assumptions (5)
- domain assumption The Koonin-Pratt formula (Eq. 2) with pair isolation and the smoothness approximation q_emit approximately q (footnote 1, Sec. 2)
- domain assumption The two-body interaction is described by a short-range, local, central potential V(r) (Eq. 3, Sec. 2)
- standard math Total probability (flux) conservation for the asymptotic wave function (Eq. 21, Sec. 3.2)
- domain assumption The relative source function is spherical and q-independent (S(r) = S(|r|), Sec. 2 and 3.1)
- standard math The plane wave admits the delta-function asymptotic representation (Eq. 28) with the stated convention for delta(z)
Cite this review
Pith. "Pith review of Higher partial waves in femtoscopy." pith.science (2026). https://pith.science/paper/QCTSJCVW
@misc{pith2026241108541,
author = {Pith},
title = {Pith review of: Higher partial waves in femtoscopy},
year = {2026},
howpublished = {\url{https://pith.science/paper/QCTSJCVW}},
note = {Machine review of arXiv:2411.08541}
}
abstract
Femtoscopy is recently gaining more attention as a new approach complementary to scattering experiments for constraining hadron-hadron interactions. We discuss the effect of higher partial waves on the two-particle correlation function, which has been neglected in traditional formulae used in the femtoscopy analyses. We consider the partial-wave expansion of the wave function in the Koonin-Pratt formula to give the correction to the correlation function by a sum of the contributions from each partial wave. We also generalize the Lednicky-Lyuboshitz formula, which was originally derived for the s-wave interaction, for higher partial waves. We find a compact representation of the generalized Lednicky-Lyuboshitz formula given by the backward scattering amplitude $f(\theta = \pi)$ and the Fourier-Laplace transform of the relative source function, which gives an insight into the structure of the Lednicky-Lyuboshitz formula and its relation to the optical theorem. We numerically demonstrate the significance of higher partial waves with resonances using the square potential well. Also, the generalized Lednicky-Lyuboshitz formula turned out to be broken for higher partial waves, which suggests the importance of the centrifugal force for the higher partial waves.
Figures
Forward citations
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Corrections to the Smoothness and On-Shell Approximations in Femtoscopy and Coalescence
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Reference graph
Works this paper leans on
-
[1]
Can We Extract Lambda-Lambda Interaction from Two-Particle Momentum Correlation ?
A. Ohnishi, Y. Hirata, Y. Nara, S. Shinmura, Y. Akaishi, Can we extract Lambda-Lambda interaction from two particle momentum correlation?, Nucl. Phys. A 670 (2000) 297–300. arXiv:nucl-th/9903021, doi:10. 1016/S0375-9474(00)00117-2
work page Pith review arXiv 2000
-
[2]
K. Morita, T. Furumoto, A. Ohnishi, ΛΛ interaction from relativistic heavy-ion collisions, Phys. Rev. C 91 (2) (2015) 024916. arXiv:1408. 6682, doi:10.1103/PhysRevC.91.024916
-
[3]
S. Cho, T. Hyodo, D. Jido, C. M. Ko, S. H. Lee, S. Maeda, K. Miyahara, K. Morita, M. Nielsen, A. Ohnishi, T. Sekihara, T. Song, S. Yasui, K. Yazaki, Exotic hadrons from heavy ion collisions, Progress in Particle and Nuclear Physics 95 (2017) 279–322. arXiv:1702.00486, doi:https://doi.org/10.1016/j.ppnp.2017.02.002. 16 URL https://www.sciencedirect.com/sci...
arXiv 2017
-
[4]
L. Fabbietti, V. Mantovani Sarti, O. Vazquez Doce, Study of the Strong Interaction Among Hadrons with Correlations at the LHC, Ann. Rev. Nucl. Part. Sci. 71 (2021) 377–402. arXiv:2012.09806, doi:10.1146/ annurev-nucl-102419-034438
arXiv 2021
-
[5]
Adamczyk, et al., ΛΛ Correlation Function in Au+Au collisions at√sN N = 200 GeV, Phys
L. Adamczyk, et al., ΛΛ Correlation Function in Au+Au collisions at√sN N = 200 GeV, Phys. Rev. Lett. 114 (2) (2015) 022301. arXiv: 1408.4360, doi:10.1103/PhysRevLett.114.022301
arXiv 2015
-
[6]
Adamczyk, et al., Measurement of Interaction between Antipro- tons, Nature 527 (2015) 345–348
L. Adamczyk, et al., Measurement of Interaction between Antipro- tons, Nature 527 (2015) 345–348. arXiv:1507.07158, doi:10.1038/ nature15724
arXiv 2015
-
[7]
S. Acharya, et al., p-p, p-Λ and Λ-Λ correlations studied via femtoscopy in pp reactions at √s = 7 TeV, Phys. Rev. C 99 (2) (2019) 024001. arXiv:1805.12455, doi:10.1103/PhysRevC.99.024001
arXiv 2019
-
[8]
S. Acharya, et al., First Observation of an Attractive Interaction be- tween a Proton and a Cascade Baryon, Phys. Rev. Lett. 123 (11) (2019) 112002. arXiv:1904.12198, doi:10.1103/PhysRevLett.123.112002
arXiv 2019
Show all 29 references
-
[9]
Acharya, et al., Investigation of the p–Σ0 interaction via femtoscopy in pp collisions, Phys
S. Acharya, et al., Investigation of the p–Σ0 interaction via femtoscopy in pp collisions, Phys. Lett. B 805 (2020) 135419. arXiv:1910.14407, doi:10.1016/j.physletb.2020.135419
2020 arXiv
-
[10]
Acharya, et al., Scattering studies with low-energy kaon-proton fem- toscopy in proton-proton collisions at the LHC, Phys
S. Acharya, et al., Scattering studies with low-energy kaon-proton fem- toscopy in proton-proton collisions at the LHC, Phys. Rev. Lett. 124 (9) (2020) 092301. arXiv:1905.13470, doi:10.1103/PhysRevLett.124. 092301
2020 arXiv
-
[11]
Acharya, et al., Study of the Λ-Λ interaction with femtoscopy corre- lations in pp and p-Pb collisions at the LHC, Phys
S. Acharya, et al., Study of the Λ-Λ interaction with femtoscopy corre- lations in pp and p-Pb collisions at the LHC, Phys. Lett. B 797 (2019) 134822. arXiv:1905.07209, doi:10.1016/j.physletb.2019.134822
2019 arXiv
-
[12]
Collaboration, et al., Unveiling the strong interaction among hadrons at the LHC, Nature 588 (2020) 232–238, [Erratum: Nature 590, E13 (2021)]
A. Collaboration, et al., Unveiling the strong interaction among hadrons at the LHC, Nature 588 (2020) 232–238, [Erratum: Nature 590, E13 (2021)]. arXiv:2005.11495, doi:10.1038/s41586-020-3001-6 . 17
2020 arXiv
-
[13]
Acharya, et al., Exploring the NΛ–NΣ coupled system with high precision correlation techniques at the LHC, Phys
S. Acharya, et al., Exploring the NΛ–NΣ coupled system with high precision correlation techniques at the LHC, Phys. Lett. B 833 (2022) 137272. arXiv:2104.04427, doi:10.1016/j.physletb.2022.137272
2022 arXiv
-
[14]
Acharya, et al., Investigating the role of strangeness in baryon–antibaryon annihilation at the LHC, Phys
S. Acharya, et al., Investigating the role of strangeness in baryon–antibaryon annihilation at the LHC, Phys. Lett. B 829 (2022) 137060. arXiv:2105.05190, doi:10.1016/j.physletb.2022.137060
2022 arXiv
-
[15]
Acharya, et al., Experimental Evidence for an Attractive p- ϕ Inter- action, Phys
S. Acharya, et al., Experimental Evidence for an Attractive p- ϕ Inter- action, Phys. Rev. Lett. 127 (17) (2021) 172301. arXiv:2105.05578, doi:10.1103/PhysRevLett.127.172301
2021 arXiv
-
[16]
Acharya, et al., Kaon–proton strong interaction at low relative mo- mentum via femtoscopy in Pb–Pb collisions at the LHC, Phys
S. Acharya, et al., Kaon–proton strong interaction at low relative mo- mentum via femtoscopy in Pb–Pb collisions at the LHC, Phys. Lett. B 822 (2021) 136708. arXiv:2105.05683, doi:10.1016/j.physletb. 2021.136708
2021 arXiv
-
[17]
Acharya, et al., First measurement of the Λ–Ξ interaction in pro- ton–proton collisions at the LHC, Phys
S. Acharya, et al., First measurement of the Λ–Ξ interaction in pro- ton–proton collisions at the LHC, Phys. Lett. B 844 (2023) 137223. arXiv:2204.10258, doi:10.1016/j.physletb.2022.137223
2023 arXiv
-
[18]
Acharya, et al., First study of the two-body scattering involving charm hadrons, Phys
S. Acharya, et al., First study of the two-body scattering involving charm hadrons, Phys. Rev. D 106 (5) (2022) 052010. arXiv:2201.05352, doi: 10.1103/PhysRevD.106.052010
2022 arXiv
-
[19]
Acharya, et al., Constraining the KN coupled channel dynamics using femtoscopic correlations at the LHC, Eur
S. Acharya, et al., Constraining the KN coupled channel dynamics using femtoscopic correlations at the LHC, Eur. Phys. J. C 83 (4) (2023) 340. arXiv:2205.15176, doi:10.1140/epjc/s10052-023-11476-0
2023 arXiv
-
[20]
Acharya, et al., Accessing the strong interaction between Λ baryons and charged kaons with the femtoscopy technique at the LHC, Phys
S. Acharya, et al., Accessing the strong interaction between Λ baryons and charged kaons with the femtoscopy technique at the LHC, Phys. Lett. B 845 (2023) 138145. arXiv:2305.19093, doi:10.1016/j. physletb.2023.138145
2023 arXiv
-
[21]
Acharya, et al., Studying the interaction between charm and light- flavor mesons, Phys
S. Acharya, et al., Studying the interaction between charm and light- flavor mesons, Phys. Rev. D 110 (3) (2024) 032004. arXiv:2401.13541, doi:10.1103/PhysRevD.110.032004
2024 arXiv
-
[22]
S. E. Koonin, Proton Pictures of High-Energy Nuclear Collisions, Phys. Lett. B 70 (1977) 43–47. doi:10.1016/0370-2693(77)90340-9 . 18
1977 doi
-
[23]
Pratt, Pion Interferometry for Exploding Sources, Phys
S. Pratt, Pion Interferometry for Exploding Sources, Phys. Rev. Lett. 53 (1984) 1219–1221. doi:10.1103/PhysRevLett.53.1219
1984 doi
-
[24]
Bauer, C
W. Bauer, C. K. Gelbke, S. Pratt, Hadronic interferometry in heavy ion collisions, Ann. Rev. Nucl. Part. Sci. 42 (1992) 77–100. doi:10.1146/ annurev.ns.42.120192.000453
1992
-
[25]
Lednicky, V
R. Lednicky, V. L. Lyuboshits, Final State Interaction Effect on Pairing Correlations Between Particles with Small Relative Momenta, Yad. Fiz. 35 (1981) 1316–1330
1981
-
[26]
Kamiya, T
Y. Kamiya, T. Hyodo, K. Morita, A. Ohnishi, W. Weise, K −p Corre- lation Function from High-Energy Nuclear Collisions and Chiral SU(3) Dynamics, Phys. Rev. Lett. 124 (13) (2020) 132501.arXiv:1911.01041, doi:10.1103/PhysRevLett.124.132501
2020 arXiv
-
[27]
Viviani, S
M. Viviani, S. K¨ onig, A. Kievsky, L. E. Marcucci, B. Singh, O. V´ azquez Doce, Role of three-body dynamics in nucleon-deuteron correlation functions, Phys. Rev. C 108 (6) (2023) 064002. arXiv: 2306.02478, doi:10.1103/PhysRevC.108.064002
2023 arXiv
-
[28]
Rzesa, M
W. Rzesa, M. Stefaniak, S. Pratt, Theoretical description of proton- deuteron interactions using exact two-body dynamic of femtoscopic cor- relation method (10 2024). arXiv:2410.13983
2024 arXiv
-
[29]
J. M. Torres-Rincon, A. Ramos, J. Ruf ´ ı, A two-body femtoscopy ap- proach to the proton-deuteron correlation function (10 2024). arXiv: 2410.23853. 19 1×10−10 1×10−8 1×10−6 0.0001 0.01 1 0 50 100 150 200 250 300 350 400 (a) |ΔCl(q)| q (MeV) l = 0 l = 1 l = 2 l = 3 1×10−35 1×...
2024 arXiv
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