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REVIEW 2 major objections 3 minor 22 references

Recent results on heavy flavours and quarkonia from ALICE

T0 review · 2 major / 3 minor · reviewed 2026-08-12 · deepseek-v4-flash

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Pith's one-line read Heavy quarks fragment differently in hadronic collisions than in electron-positron collisions.

desk verdict A capable ALICE proceedings survey whose real value is the Run 3 preliminary data points; the headline non-universality claim is borrowed from the published analyses it cites, and the energy confound in the fragmentation-fraction comparison is not addressed here. read the letter →

arxiv 2411.11444 v1 pith:IFHTFGF7 submitted 2024-11-18 nucl-ex hep-ex

Fiorella Fionda (on behalf of the ALICE Collaboration) This is my paper · ORCID
classification nucl-exhep-ex
keywords heavy-flavourhadronisationcharmfragmentationfractionsbeautybaryonsuniversalityquark-gluonplasmaproton-protoncollisionsproton-leadquarkonia
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

These proceedings argue that the fraction of charm and beauty quarks ending up in a given hadron species is not the same in every collision environment. Measurements in proton-proton and proton-lead collisions show more charm baryons and fewer charm mesons than comparable yields from electron-positron and electron-proton collisions. If that is right, hadronisation models tuned only to lepton-collision data will systematically under-predict baryon production at hadron colliders, and hadronisation parameters will need to be constrained with hadronic collision data. The reported charm fragmentation fractions agree between pp and p-Pb collisions, so the effect appears to depend on the parton-rich hadronisation environment rather than on the size of the collision system.

What carries the argument

The load-bearing objects are the fragmentation fractions $f(c\to h)$, the fraction of all charm quarks that hadronise into a particular species $h$, obtained by combining measured $p_{\mathrm{T}}$-differential yields and comparing them across pp, p-Pb, $e^+e^-$, and $ep$ data. A second diagnostic is the excited-to-ground charm-baryon yield ratio $\Sigma_c^{0,++}(2520)/\Sigma_c^{0,++}(2455)$, which tests how much of the baryon enhancement comes from feed-down of excited states. The argument proceeds by showing that model calculations inheriting their fragmentation fractions from $e^+e^-$ data under-predict the measured baryon-to-meson ratios, while calculations that add colour reconnection beyond leading colour or coalescence come closer.

What would settle it

Measure the charm baryon-to-meson ratio in pp collisions as a function of charged-particle multiplicity over the full $p_{\mathrm{T}}$ range; if the ratio is flat with multiplicity, the parton-rich-environment explanation fails, and if re-extracting $f(c\to h)$ with different low- and high-$p_{\mathrm{T}}$ extrapolations removes the enhancement, the non-universality claim collapses.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that the fragmentation fractions of heavy quarks are not universal. The charm fragmentation fractions $f(c\to h)$ measured through the combined yields of $D^0$, $D^+$, $D_s^+$, $\Lambda_c^+$, $\Xi_c^0$, and $J/\psi$ in pp collisions at 5.02 TeV and in p-Pb collisions at 5.02 TeV agree with each other, showing no dependence on collision system size, while they differ systematically from the fractions extracted from $e^+e^-$ and $ep$ collisions at lower energies. The baryon fractions are enhanced and the meson fractions are diminished relative to the leptonic values. The paper reads this as confirmation that heavy-quark hadronisation in a parton-rich environment is different from vacuum-like fragmentation.

Load-bearing premise

The comparison assumes that the baryon/meson differences come from the hadronisation environment rather than from the very different centre-of-mass energies or initial-state quark content of the compared collision systems, and that the quoted fragmentation fractions survive the integration over unmeasured low- and high-$p_{\mathrm{T}}$ regions.

Editorial extensions

If this is right

  • If $f(c\to h)$ is system dependent, fragmentation fits based only on $e^+e^-$ or $ep$ data will mis-predict charm and beauty baryon yields at hadron colliders; hadronisation parameters must be fitted to pp and p-Pb data.
  • Because the pp and p-Pb fractions agree, cold nuclear matter effects cannot be the origin of the baryon enhancement; the driver is common to hadronic collisions, plausibly the parton-rich environment.
  • The default PYTHIA 8 Monash tune under-predicts the measured $D_s^+/D^+$ ratio, while the coalescence-plus-fragmentation calculation describes it better, so production models need coalescence or an equivalent mechanism.
  • The elevated $\Lambda_c^+/D^0$ and $\Xi_c^0/D^0$ ratios imply sizeable feed-down from excited charm baryons, and the $\Sigma_c(2520)/\Sigma_c(2455)$ ratio provides a direct constraint on how much of the enhancement is resonance decay rather than direct baryon production.

Reading between the lines

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

  • A natural extension the paper does not make: if the parton-rich environment drives the baryon enhancement, the enhancement should grow with final-state multiplicity inside pp collisions, so $\Lambda_c^+/D^0$ should rise with charged-particle multiplicity; Run 3 data could test this directly.
  • The quoted comparison bundles collision species with collision energy, since pp and p-Pb at several TeV are compared with $e^+e^-$ and $ep$ at much lower energies; extracting $f(c\to h)$ from $e^+e^-$ at LHC-scale energies, or from pp data over a wide energy range, would separate the two.
  • If the pattern is universal for heavy quarks, the same shift should appear in beauty hadrons; a forward-rapidity beauty-baryon measurement already hints at it, and precise beauty fragmentation fractions would confirm or refute the extension.
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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

2 major / 3 minor

Summary. This proceedings contribution from the ALICE Collaboration reviews recent heavy-flavour and quarkonium measurements in pp, p-Pb, and Pb-Pb collisions, with emphasis on Run 3 preliminary results. It presents inclusive J/psi production in pp at 13.6 TeV, the D_s^+/D^+ ratio in pp at 13.6 TeV, the excited-to-ground Sigma_c baryon ratio, and fragmentation fractions of charm hadrons in p-Pb collisions compared with pp and leptonic collisions. The central claim is that charm fragmentation fractions are not universal: baryon fractions are enhanced and meson fractions suppressed in hadronic collisions relative to e+e- and ep collisions, and the paper attributes this to hadronisation in a parton-rich environment rather than in-vacuum fragmentation. The paper also reports a model-tuning exercise for the Sigma_c ratio and comparisons of prompt J/psi nuclear modification factors with theoretical models.

Significance. If the non-universality of charm fragmentation fractions is established, it is an important result for heavy-flavour hadronisation: Monte Carlo generators and coalescence models would need to be constrained by hadronic-collision data rather than leptonic data alone. The paper honestly reports large uncertainties in several comparisons and explicitly states where models cannot be discriminated and where no enhancement is observed. It also shows new high-granularity Run 3 measurements that extend to lower pT and will serve as useful inputs for model tuning. The claim is significant for the field, but its strength currently exceeds what the controlled comparisons in this document support.

major comments (2)
  1. [Section 3, Fig. 4 (right)] The central claim that fragmentation fractions are non-universal and that the difference arises from a parton-rich hadronisation environment is not controlled for collision energy or initial-state parton content. The comparison in Fig. 4 (right) places pp at sqrt(s)=5.02 TeV and p-Pb at sqrt(s_NN)=5.02 TeV against e+e- at 10.5 GeV and at the Z pole and ep at HERA energies, which spans roughly two orders of magnitude in centre-of-mass energy and different initial-state flavours. The observed baryon enhancement and meson suppression could therefore be an energy-dependent fragmentation or feed-down effect rather than an environment effect. The only direct energy-dependence evidence presented is the D_s^+/D^+ ratio in pp at 5-13.6 TeV (Fig. 2), which concerns a single meson ratio rather than the full set of fragmentation fractions. Please either provide explicit evidence that f(c -> h) is energy-independent within hadronic collisions or temper the wording so that the conclusion is stated as a comparison to lower-energy leptonic collisions, not as an unambiguous proof of a parton-rich-environment effect.
  2. [Section 3, Fig. 4 (right)] The quoted fragmentation fractions f(c -> h) require integrating or extrapolating measured pT-differential yields over the full pT range, but the manuscript does not describe the integration limits, the extrapolation procedure, or the associated systematic uncertainties. If the unmeasured low- and high-pT regions contribute substantially to the total yields, the displayed differences between hadronic and leptonic collisions could be affected. Please add at least a sentence specifying how the fragmentation fractions are obtained and what uncertainty is assigned to the extrapolation, or refer explicitly to the analysis in Ref. [20] where this is documented.
minor comments (3)
  1. [Section 2, Fig. 3 (right)] The sentence stating that the Sigma_c(2520)/Sigma_c(2455) ratio 'can be reproduced' by PYTHIA 8 CR-BLC after tuning one parameter on the measured Lambda_c (from Sigma_c)/Lambda_c ratio describes a fit rather than an independent prediction. The wording should be adjusted to make clear that the agreement is obtained after tuning, for example by saying 'can be described after tuning...' or 'is consistent with the calculation once the parameter is fitted to the Lambda_c ratio.'
  2. [Abstract] The phrase 'unforeseen features' is vague; specifying the actual pattern, such as 'an enhanced baryon-to-meson ratio for charm hadrons', would make the abstract more informative for a reader who does not continue to the body.
  3. [Section 1, Ref. [18]] Reference [18] is given only as an arXiv identifier without a version or a journal reference; adding a more complete citation would help readers locate the tuned-parameter details.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: data-summary proceedings with disclosed model tuning; central claims are empirical comparisons.

full rationale

The paper is a proceedings summary of ALICE measurements. The central claim that charm fragmentation fractions are non-universal (Section 3, Fig. 4 right) is an empirical comparison of measured f(c->h) values in pp/p-Pb versus e+e-/ep; it is not derived from a fitted parameter or from a self-citation. The only model-tuning episode (Section 2, Fig. 3 right) is explicitly disclosed: a PYTHIA 8 CR-BLC parameter is tuned on the measured Lambda_c(from Sigma_c)/Lambda_c ratio and then used to reproduce the distinct Sigma_c(2520)/Sigma_c(2455) ratio, with details deferred to Ref. [18]. Because the tuning target and the reproduced observable are different quantities, this is a calibration/postdiction rather than a circular reduction. The many ALICE self-references are to the collaboration's own independent measurements and to published model papers; they are not load-bearing assumptions that smuggle in the conclusion. The energy/initial-state difference between hadronic and leptonic collisions noted by a skeptic is a potential confound for the non-universality interpretation, but it is not circularity under the definitions used here.

Assumptions & free parameters 1 free parameters · 4 assumptions · 0 invented entities

The paper is a measurement summary, so it introduces few free parameters, axioms, or entities of its own. The central physics claim (non-universal fragmentation) rests on standard QCD factorisation and on the assumption that cross-system and cross-energy comparisons are meaningful. The one parameter tuned within this text is the PYTHIA 8 CR-BLC diquark spin-suppression parameter. No new entities are postulated. The heavier theoretical machinery (NRQCD, CEM, statistical hadronisation, coalescence models) is inherited from cited works, not derived here.

free parameters (1)
  • PYTHIA 8 CR-BLC diquark spin-suppression parameter = Not quoted in the paper
    Tuned on the measured Lambda_c (from Sigma_c) / Lambda_c production yield ratio so that the model matches the Sigma_c(2520)/Sigma_c(2455) ratio in Fig. 3 (right); the procedure is referenced to Altmann et al., arXiv:2405.19137v2. The paper does not give the fitted value.
assumptions (4)
  • standard math QCD factorisation: heavy-flavour hadron production is the convolution of PDFs, the partonic cross-section, and fragmentation (Collins et al., Adv. Ser. Direct. High Energy Phys. 5 (1989) 1).
    Invoked in Section 1 as the framework for interpreting all cross sections discussed; the fragmentation step is the object being tested.
  • domain assumption Universality of fragmentation fractions was the prior baseline: the same hadronisation in e+e-, ep and hadronic collisions.
    This is the assumption the paper argues is false; it is inherited from the factorisation programme and is the null hypothesis for the claimed non-universality.
  • domain assumption No significant centre-of-mass-energy dependence in heavy-quark fragmentation fractions across 10.5 GeV (e+e-) to 13.6 TeV (pp).
    The cross-system comparison in Fig. 4 (right) and the abstract's claim of non-universality assume the observed baryon/meson differences are due to the collision environment rather than the energy difference; the paper does not test this directly.
  • domain assumption The measured pT-differential yields can be integrated or extrapolated to obtain total fragmentation fractions f(c -> h).
    The fragmentation-fraction comparison in Fig. 4 (right) requires full-pT coverage or extrapolation; the paper does not quantify the extrapolation uncertainty in the displayed fractions.

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Cite this review

Pith. "Pith review of Recent results on heavy flavours and quarkonia from ALICE." pith.science (2026). https://pith.science/paper/IFHTFGF7

@misc{pith2026241111444,
  author       = {Pith},
  title        = {Pith review of: Recent results on heavy flavours and quarkonia from ALICE},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/IFHTFGF7}},
  note         = {Machine review of arXiv:2411.11444}
}
abstract

Heavy-flavour hadrons, containing at least one charm or beauty quark, are excellent probes of the deconfined medium created in ultra-relativistic heavy-ion collisions, known as quark-gluon plasma. Results in smaller collision systems, such as proton-proton and p-Pb collisions, besides representing an important baseline for interpreting heavy-ion measurements, are crucial to test perturbative QCD calculations and hadronisation mechanisms in the absence of hot medium effects, as well as to search for commonalities with heavy-ion systems. Recently, measurements in proton-proton and p-Pb collisions have revealed unforeseen features with respect to the expectations based on previous results from ${\rm e}^{+}{\rm e}^{-}$ and ep collisions, showing that fragmentation fractions of heavy quarks are not universal. In this contribution, an overview of the most recent ALICE heavy-flavour measurements, along with the comparison to available calculations, will be discussed.

Figures

Figures reproduced from arXiv: 2411.11444 by the authors.

Figure 1
Figure 1. Inclusive J/ψ cross section measured at midrapidity in pp collisions at √ s = 13.6 TeV com￾pared to similar measurements from ALICE and ATLAS at √ s = 13 TeV in the left panel (see references on the plot) and with several charmonium production models [12–15] coupled to FONLL [16] in the right panel. 0 5 10 15 20 25 30 35 /V (Ge c) T p 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 + 1 /D + s D ALICE Preliminary pp collisions… view at source ↗
Figure 2
Figure 2. Prompt D+ s /D + production yield ratio measured at midrapidity in pp collisions at √ s = 13.6 TeV compared to similar measurements at lower centre-of-mass energies from Run 2 in the left panel (see references on the plot) and with model calculations [6–9] in the right panel. panel of [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Relative production of the Σ 0,++ c (2520) baryon to the ground state Σ 0,++ c (2455) measured at midrapidity in pp collisions at √ s = 13.6 TeV. In the left panel, it is compared with model calcula￾tions [6, 7, 10, 17] and to lower energy results from Belle Collaboration (see reference on the plot). In the right panel, the ratio is compared with PYTHIA 8 CR-BLC calculations [7] after tuning one param￾eter of the mo… view at source ↗
Figures from the paper (2 more)
Figure 4
Figure 4. Figure 4: Left panel: prompt Ξ 0 c pT-differential cross section in p–Pb collisions at √ sNN = 5.02 TeV compared with POWHEG+PYTHIA 6 simulations coupled to the EPPS16 nPDF parametrisation and to QCM (see [19] and references therein). Right panel: fragmentation fractions for cha…
Figure 5
Figure 5. Figure 5: Left panel: pT-differential prompt J/ψ RAA measured at midrapidity in Pb–Pb collisions (0– 10% centrality class) at √ sNN = 5.02 TeV compared to similar measurements from other experiments and with theoretical models (see [21] and references therein). Right panel: prom…

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Reference graph

Works this paper leans on

22 extracted references · 19 canonical work pages

  1. [20]

    et al., ALICE Collaboration, arXiv:2405.14571

    Acharya, S. et al., ALICE Collaboration, arXiv:2405.14571

    arXiv

  2. [1]

    Collins, J. C. et al., Adv. Ser. Direct. High Energy Phys. 5, 1–91 (1989)

    work page 1989

  3. [2]

    et al., Eur

    Andronic, A. et al., Eur. Phys. J. C 76, 3 (2016)

    work page 2016

  4. [3]

    et al., ALICE Collaboration, Phys

    Acharya, S. et al., ALICE Collaboration, Phys. Rev. C 107 064901 (2023)

    work page 2023

  5. [4]

    et al., ALICE Collaboration, JHEP 10 159 (2021)

    Acharya, S. et al., ALICE Collaboration, JHEP 10 159 (2021)

    work page 2021

  6. [5]

    et al., LHCb Collaboration, Phys

    Aaij, R. et al., LHCb Collaboration, Phys. Rev. D 100, 031102 (2019)

    work page 2019

  7. [6]

    et al., Eur

    Skands, P. et al., Eur. Phys. J. C 74 3024 (2014)

    work page 2014

  8. [7]

    Christiansen J. R. and Skands P., JHEP 08 003 (2015)

    work page 2015

Show all 22 references
  1. [8]

    et al., Phys

    Greco, V . et al., Phys. Lett. B 821 136622 (2021)

    2021

  2. [9]

    et al., arXiv:2306.02152

    Beraudo, A. et al., arXiv:2306.02152

    arXiv

  3. [10]

    and Rapp R., Phys

    He M. and Rapp R., Phys. Lett. B 795 117 (2019)

    2019

  4. [11]

    et al., ALICE Collaboration, JINST 19 P05062 (2024)

    Acharya, S. et al., ALICE Collaboration, JINST 19 P05062 (2024)

    2024

  5. [12]

    and Kniehl B

    Butenschön M. and Kniehl B. A., Phys. Rev. Lett. 106 022003 (2011)

    2011

  6. [13]

    et al., Phys

    Ma, Y .-Q. et al., Phys. Rev. Lett. 106 042002 (2011)

    2011

  7. [14]

    and Venugopalan R., Phys

    Ma Y .-Q. and Venugopalan R., Phys. Rev. Lett.113 192301 (2014)

    2014

  8. [15]

    and V ogt R., Phys

    Cheung V . and V ogt R., Phys. Rev. D98 114029 (2018)

    2018

  9. [16]

    et al., JHEP 05 007 (1998)

    Cacciari, M. et al., JHEP 05 007 (1998)

    1998

  10. [17]

    et al., Phys

    Andronic, A. et al., Phys. Lett. B 797 134836 (2019)

    2019

  11. [18]

    et al., arXiv:2405.19137v2

    Altmann J. et al., arXiv:2405.19137v2

    arXiv

  12. [19]

    et al., ALICE Collaboration, arXiv:2405.14538

    Acharya, S. et al., ALICE Collaboration, arXiv:2405.14538

    arXiv

  13. [21]

    et al., ALICE Collaboration, JHEP 02 066 (2024)

    Acharya, S. et al., ALICE Collaboration, JHEP 02 066 (2024)

    2024

  14. [22]

    et al., ALICE Collaboration, CERN-LHCC-2024-003 (2024)

    Acharya, S. et al., ALICE Collaboration, CERN-LHCC-2024-003 (2024)

    2024

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