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REVIEW 2 major objections 4 minor 14 references

New Pb-Pb data: psi(2S)-to-J/psi ratio is flat, half of pp

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2026-08-04 22:02 UTC pith:W7U3PFXW

load-bearing objection New preliminary Run 3 psi(2S)/J/psi ratio is real, but the factor-2 suppression magnitude hinges on an undocumented pp reference. the 2 major comments →

arxiv 2509.07513 v1 pith:W7U3PFXW submitted 2025-09-09 nucl-ex hep-ex

Proceedngs of Charmonium production in heavy-ion collisions, Quark Matter 2025

Ingrid McKibben Lofnes (for the ALICE Collaboration) This is my paper
classification nucl-ex hep-ex PACS 25.75.-q
keywords charmoniumquark-gluon plasmaJ/psi suppressionpsi(2S)nuclear modification factorheavy-ion collisionsregenerationbeauty quark energy loss
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

These proceedings present the ALICE Collaboration's latest charmonium measurements in lead-lead collisions and argue that the relative yield of the excited state psi(2S) to the ground state J/psi is a sharp probe of how the quark-gluon plasma melts bound charm pairs. The new preliminary Run 3 result at sqrt(s_NN)=5.36 TeV shows that this ratio is flat as collisions go from peripheral to central, and about a factor of two lower than in proton-proton collisions. The paper also reports the published Run 2 nuclear modification factors for prompt and non-prompt J/psi at 5.02 TeV: prompt J/psi is strongly suppressed at high momentum but rises above unity at low momentum, a signature that recombined charm pairs partially replace melted ones, while non-prompt J/psi suppression matches models with both collisional and radiative energy loss. The point of the comparison is to distinguish transport models that suppress charmonium sequentially from statistical hadronization models that reconstitute them at the phase boundary.

Core claim

The central result is a first preliminary measurement of the psi(2S)-to-J/psi production ratio in Pb-Pb collisions at sqrt(s_NN)=5.36 TeV at forward rapidity. The ratio, shown as a function of the mean number of participating nucleons, is flat within uncertainties across centrality and is suppressed by roughly a factor of two relative to the extrapolated pp reference at the same energy, consistent with the earlier Run 2 measurement but with better precision. The authors conclude that the measured psi(2S) is clearly suppressed relative to the pp-scaled distribution, and interpret the flat trend as a constraint on recombination of psi(2S) in the medium. The paper also presents the published Ru

What carries the argument

The load-bearing observable is the psi(2S)-to-J/psi ratio, formed from charmonium yields in the dimuon channel at forward rapidity. Because psi(2S) is less tightly bound than J/psi, the ratio is a direct measure of sequential suppression: if the quark-gluon plasma melts excited states more easily, the ratio drops; if recombination recreates them, the ratio should rise toward pp values in central collisions. The prompt and non-prompt separation at midrapidity uses vertex displacement from the inner tracking system, and the nuclear modification factor R_AA (yield in Pb-Pb divided by binary-scaled pp cross section) is the normalization used to compare to models.

Load-bearing premise

The magnitude of the factor-of-two suppression rests on an extrapolated pp reference ratio at sqrt(s_NN)=5.36 TeV whose systematic uncertainty is not documented in these proceedings.

What would settle it

Measure the psi(2S)-to-J/psi ratio in pp collisions at sqrt(s_NN)=5.36 TeV in the same forward-rapidity acceptance; a direct reference that differs from the extrapolation would shift the reported suppression factor and could change the flatness interpretation if the centrality trend is also re-derived.

Watch this falsifier. Get emailed when new claim-graph text bears on it.

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If this is right

  • A flat psi(2S)-to-J/psi ratio across centrality implies the suppression of the excited state is nearly saturated even in peripheral Pb-Pb collisions, so any model that predicts a strong centrality rise in the ratio is disfavored.
  • The low-p_T rise of prompt J/psi R_AA above unity supports a two-step picture: color screening and dissociation at high p_T, and regeneration of charm pairs at low p_T.
  • The non-prompt J/psi suppression, reproduced only by models with both collisional and radiative energy loss, indicates beauty quarks feel the medium through both mechanisms.
  • The higher precision of the Run 3 ratio sharpens the existing tension between transport calculations (TAMU) and statistical hadronization (SHMc), which differ in whether recombination happens continuously or only at the phase boundary.
  • With the newly installed muon forward tracker, prompt and non-prompt charmonium will become separable at forward rapidity, extending beauty-energy-loss studies to a region with few data.

Where Pith is reading between the lines

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

  • The reported factor-of-two suppression is anchored to an extrapolated pp reference ratio at 5.36 TeV that is not documented in depth in these proceedings; a direct pp measurement at the same energy is the cleanest check on the absolute magnitude.
  • If the flatness persists with higher Run 3 statistics, it would strengthen the sequential-suppression picture and place a bound on psi(2S) regeneration, because substantial recombination in central collisions should push the ratio upward.
  • The same ground/excited-state logic applied to bottomonium predicts a Upsilon(2S)-to-Upsilon(1S) ratio with a similar flat-and-suppressed shape in Pb-Pb, which can be tested with the existing dimuon data.
  • The centrality-flat ratio could serve as a baseline for cold-nuclear-matter effects once same-energy p-Pb measurements become available, helping separate initial-state and final-state suppression.

Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

2 major / 4 minor

Summary. These proceedings, by I. M. Lofnes on behalf of the ALICE Collaboration, summarize charmonium measurements in heavy-ion collisions. The paper reviews the published Run 2 ALICE results on prompt and non-prompt J/psi nuclear modification factors in Pb--Pb collisions at sqrt(s_NN)=5.02 TeV, comparing them to transport, statistical hadronization, and energy-loss models. It then presents a new preliminary Run 3 measurement of the psi(2S)-to-J/psi ratio at forward rapidity in Pb--Pb collisions at sqrt(s_NN)=5.36 TeV. The conclusions state that this ratio is suppressed by about a factor of two relative to pp collisions and is flat as a function of centrality within uncertainties. The model comparisons are qualitative, with TAMU and SHMc calculations shown alongside the Run 3 data.

Significance. If the new Run 3 measurement is established, it would provide the first psi(2S)-to-J/psi ratio at sqrt(s_NN)=5.36 TeV in Pb--Pb collisions and could sharpen discrimination between regeneration-based transport models and statistical hadronization scenarios. The paper correctly builds on peer-reviewed Run 2 measurements [2,13] and makes comparisons only to already published models, so there is no parameter fitting or circularity in the model comparison. The main value is the preliminary Run 3 data point and its potential for improved precision. However, the quantitative claim of 'factor 2 suppression' is not independently supported within the paper itself, because it relies on an undocumented extrapolated pp reference. The qualitative interpretation of the Run 2 results is sound, but the central new quantitative conclusion needs additional support.

major comments (2)
  1. [Section 2, Fig. 2, Conclusions] The central new quantitative claim is the 'factor 2 suppression with respect to pp collisions' stated in the Conclusions and Section 2. This factor is not directly measured: it is obtained by dividing the Pb-Pb psi(2S)-to-J/psi ratio by a pp reference that is described only as 'an extrapolation of the pp ratio at the Pb-Pb collision energy' (Section 2, left panel of Fig. 2). No functional form, input data, or systematic uncertainty for this extrapolation is given, and the overlaid pp curve in the left panel has no uncertainty band. If the pp reference has an uncertainty of 15-20%, the quoted factor 2 could shift to ~1.6-2.4, which would change the model comparison. This is a load-bearing point because the 'factor 2' wording is a headline result. The paper should either provide a quantitative account of the pp extrapolation, including its systematic uncertainty, or restrict the claim to t
  2. [Section 2, Fig. 2 right] The right panel of Fig. 2 shows the new Run 3 ratio, and the text states that the improved precision 'may help in discriminating between different theoretical approaches.' As presented, however, the comparison to TAMU and SHMc is purely visual. There are no numerical values for the measured ratio, no uncertainty decomposition, and no quantitative measure of agreement with the model curves. Since the data are preliminary and appear only as plots, it is not possible to reproduce the stated factor of two or to assess the claimed precision increase over Run 2. At minimum, the paper should reference an ALICE preliminary data source or provide a table of the central values and total uncertainties for the points in Fig. 2 right.
minor comments (4)
  1. [Title and Abstract] The title contains a typo: 'Proceedngs' should be 'Proceedings.' The Abstract also says 'forseen,' likely intended as 'foreseen.'
  2. [Section 2, Fig. 2 caption] The caption of Fig. 2 left is garbled: 'c > 0.7 GeV/µ Tp , c < 20 GeV/Tp' should read something like 'pT > 0.7 GeV/c, pT < 20 GeV/c.' The render should be corrected.
  3. [Section 2, Fig. 2 left] The text refers to 'an extrapolation of the pp ratio at the Pb-Pb collision energy' to rescale the psi(2S), while the caption describes 'expectations without the QGP.' These are not obviously identical: the latter could include cold-nuclear-matter effects, whereas the former is a pp baseline. The distinction should be clarified.
  4. [Section 2] The statement that the Run 3 measurement is 'compatible to previous Run 2 results [13], but with higher precision' would be more informative if the improvement in precision were quantified (for example, uncertainty on the ratio in a common centrality bin).

Circularity Check

0 steps flagged

No circularity identified: the proceedings report direct measurements and compare them with published external models; the pp-reference extrapolation is an undocumented limitation, not a circular construction.

full rationale

This paper is an experimental measurement report, not a derivation. The central new result is the preliminary Run 3 psi(2S)-to-J/psi ratio in Pb-Pb collisions at sqrt(s_NN)=5.36 TeV (Fig. 2, right), which is directly measured from the invariant-mass distribution. No parameter is fitted in the paper, and no theoretical prediction is generated from the data. Comparisons are made to pre-existing published models (Zhou et al., SHMc, TAMU, etc.), and the data are not defined in terms of those models. The only possible concern raised by the text is the 'factor 2 suppression with respect to pp' claim, which rests on an extrapolated pp reference at sqrt(s_NN)=5.36 TeV (Section 2, Fig. 2 caption). That extrapolation is not documented with a functional form or systematic uncertainty, which is a legitimate limitation of the reported suppression magnitude. However, it is not circular: the Pb-Pb measured ratio is not constructed from that pp reference, and the pp reference is not fitted to the Pb-Pb data it is used to compare against. The ALICE self-citations are prior published measurements (Run 2 results) used for compatibility checks, not load-bearing justifications of the new result. No uniqueness theorem, no ansatz smuggled via citation, and no renaming of a known result appear. The derivation chain is therefore self-contained for what it claims: reporting a measurement and comparing it to external calculations.

Axiom & Free-Parameter Ledger

0 free parameters · 3 axioms · 0 invented entities

No parameters are fitted in this paper; the measurement rests on standard heavy-ion assumptions (initial hard-scattering production, detector corrections applied correctly) and on the validity of the pp reference extrapolation used for the psi(2S) suppression overlay.

axioms (3)
  • domain assumption Charmonia are produced in initial hard scatterings and experience the full QGP evolution.
    Standard assumption in heavy-ion physics, stated in the Introduction, used to motivate the probe interpretation.
  • domain assumption The ALICE detector corrections (acceptance, efficiency, centrality determination, background subtraction) are applied correctly in the preliminary Run 3 analysis.
    Required for the measured ratio and R_AA values; details are not in this proceedings.
  • domain assumption The pp reference ratio used for the psi(2S) suppression overlay is a valid extrapolation to sqrt(s_NN)=5.36 TeV.
    The overlay illustrating the factor 2 suppression uses a pp ratio extrapolated to the Pb-Pb energy; its validity and systematic uncertainty are not quantified in the paper.

pith-pipeline@v1.3.0-alltime-deepseek · 4105 in / 8784 out tokens · 87742 ms · 2026-08-04T22:02:28.538742+00:00 · methodology

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Cite this review

Pith. "Pith review of Proceedngs of Charmonium production in heavy-ion collisions, Quark Matter 2025." pith.science (2026). https://pith.science/paper/W7U3PFXW

@misc{pith2026250907513,
  author       = {Pith},
  title        = {Pith review of: Proceedngs of Charmonium production in heavy-ion collisions, Quark Matter 2025},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/W7U3PFXW}},
  note         = {Machine review of arXiv:2509.07513}
}
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read the original abstract

The early production of heavy quarks ($c\bar{c}$ and $b\bar{b}$) makes charmonia an ideal probe to study the evolution of the hot and dense medium produced in ultra-relativistic heavy-ion collisions, known as the quark--gluon plasma (QGP). At LHC energies, the well established suppression of charmonium yield from color screening in the QGP is counterbalanced by the recombination of uncorrelated charm-quark pairs, either throughout the QGP phase or solely at the phase boundary. Systematic measurements of charmonium ground and excited states are important to discriminate between the scenarios forseen by various theoretical models. In addition, studies of non-prompt charmonia, i.e., charmonia originating from the decay of beauty hadrons, give access to study the energy loss of beauty quarks in the QGP. In these proceedings we present recently published Run 2 results by the ALICE Collaboration of prompt and non-prompt J/$\psi$ measured at midrapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. In addition, the first preliminary Run 3 measurement of the $\psi$(2S)-to-J/$\psi$ ratio, measured at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$= 5.36 TeV, is shown. The results are compared to available theoretical model calculations.

Figures

Figures reproduced from arXiv: 2509.07513 by Ingrid McKibben Lofnes (for the ALICE Collaboration).

Figure 1
Figure 1. Figure 1: RAA as a function of pT for prompt (left) and non-prompt (right) J/ψ measured at midrapidity in Pb–Pb collisions at √ sNN = 5.02 TeV [2]. Theoretical model predictions for prompt [3–5] and non￾prompt [6–12] J/ψ are also shown. The non-prompt J/ψ RAA shows a strong suppression at high pT. In this region, models which include both collisional and radiative energy-loss processes describe the data within [PIT… view at source ↗
Figure 2
Figure 2. Figure 2: Left: Invariant mass distribution of µ +µ − pairs in Pb–Pb collisions at √ sNN = 5.36 TeV. The signal (blue and green) and background (gray) fit components are shown separately. In addition, the ψ(2S) component rescaled according to expectations without the QGP is shown (dashed blue). Right: ψ(2S)-to-J/ψ ratio as a function of ⟨Npart⟩ measured by ALICE at forward rapidity in Pb–Pb collisions at √ sNN = 5.0… view at source ↗

discussion (0)

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Reference graph

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