Pith. sign in

REVIEW 2 major objections 4 minor 21 references

Charm production and hadronisation in pp and p--Pb collisions at $\sqrt{s_{\rm NN}} = $ 5.02 TeV at the LHC with ALICE

T0 review · 2 major / 4 minor · reviewed 2026-08-10 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Charm fragmentation fractions measured in pp and p-Pb collisions at 5.02 TeV agree with each other, indicating that hadronisation is not modified between the two systems, while both differ from e+e- results, showing hadronisation depends…

desk verdict A clear proceedings summary of already-published ALICE charm results; the pp–pPb fragmentation-fraction comparison is asserted without a citable source. read the letter →

arxiv 2412.20939 v1 pith:7NCKM2M6 submitted 2024-12-30 hep-ex

Tiantian Cheng (on behalf of the ALICE Collaboration) This is my paper · ORCID
classification hep-ex
keywords charmproductionhadronisationfragmentationfractionsLambda_cbaryonDmesonp-Pbcollisionsheavyflavour
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 contribution presents measurements of D0, D+, Ds+, and Lambda_c+ production at midrapidity in pp and p-Pb collisions at sqrt(sNN) = 5.02 TeV. It reports the first Lambda_c+/D0 ratio in p-Pb down to pT = 0 and compares it with pp data and with model predictions. The central result is that the charm fragmentation fractions, the probabilities that a charm quark turns into each hadron species, agree between pp and p-Pb within uncertainties, suggesting that hadronisation is not modified from pp to p-Pb collisions. By contrast, these fractions differ from those measured in e+e- and ep collisions, indicating that charm hadronisation is not universal but depends on the collision system. The total charm production cross section per unit rapidity scaled by the Pb mass number is compatible between p-Pb and pp and lies on the upper edge of pQCD predictions.

What carries the argument

The central objects are the charm fragmentation fractions $f(c \to H_c)$, defined as the probability that a charm quark hadronises into a given charm-hadron species, extracted by summing the $p_{\rm T}$-integrated cross sections of the ground-state charm hadrons D0, D+, Ds+, Lambda_c+, $Xi_c^{0}$, Xi_c+ and Omega_c0 and normalising to the total charm cross section. The Lambda_c+/D0 yield ratio as a function of $p_{\rm T}$ is the diagnostic used to compare baryon and meson hadronisation; it is compared with predictions from PYTHIA 8 with colour reconnection, the Catania coalescence model, the Quark (re)-Combination Model, and the Statistical Hadronisation Model, including feed-down from excited charm baryons predicted by the Relativistic Quark Model. The feed-down correction from the yet-unmeasured excited states is the correction that carries the argument for the absolute values of the fragmentation fractions.

What would settle it

Measure the production of the excited charm baryon states that feed $\Lambda_c^+$ in both collision systems: if their feed-down contributions differ between pp and p-Pb in a way that moves the fragmentation fractions apart, the unmodified-hadronisation claim would be falsified. A sufficiently precise measurement of the $\Lambda_c^+/D^0$ ratio in p-Pb at low $p_{\rm T}$ could also reveal a genuine difference from pp, directly testing the same claim.

Watch

Extended reading notes

Core claim

The paper establishes that, within current experimental uncertainties, the charm-quark fragmentation fractions measured in p-Pb collisions at sqrt(sNN) = 5.02 TeV are consistent with those in pp collisions, so the hadronisation mechanisms are not modified from pp to p-Pb. It also establishes that the Lambda_c+/D0 ratio in p-Pb is measured for the first time down to pT = 0 and is described, within uncertainties, by the same models that describe pp data; the peak of the ratio shifts to somewhat higher pT in p-Pb, an effect the Quark (re)-Combination Model attributes to a hardening of the Lambda_c spectrum. The fragmentation fractions in both systems differ from those measured in e+e- and ep collisions, supporting the conclusion that charm hadronisation is not universal.

Load-bearing premise

The conclusion that hadronisation is unmodified from pp to p-Pb collisions assumes the feed-down correction to $\Lambda_c^+$ from unmeasured excited charm baryon states, computed with the Relativistic Quark Model, is accurate; if this correction is wrong, the reported fragmentation fractions would shift.

Editorial extensions

If this is right

  • If the central claim is correct, charm hadronisation is not universal: fragmentation functions tuned to e+e- and ep collisions underpredict charm-baryon production in hadronic collisions, so models must include recombination or colour-reconnection effects to describe pp and p-Pb data.
  • Cold nuclear matter effects and any collective phenomena present in p-Pb collisions do not change the overall pattern of charm hadronisation relative to pp at 5.02 TeV, within current uncertainties.
  • The shift of the Lambda_c+/D0 peak towards higher $p_{\rm T}$ in p-Pb, if driven by radial flow, means the baryon-to-meson ratio is sensitive to collective expansion and can be used to study it.
  • The total charm production cross section per unit rapidity in p-Pb scaled by the Pb mass number being compatible with pp supports the factorisation of charm production and provides a baseline for heavier-ion collisions.
  • Run 3 and Run 4 data with lower uncertainties will be able to test whether small differences currently hidden by uncertainties become visible.

Reading between the lines

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

  • Beyond the paper, the pp/p-Pb agreement gives a clean cold-matter baseline: any enhancement of charm-baryon production observed in Pb-Pb collisions relative to this baseline could be attributed to quark-gluon plasma effects rather than to the nuclear environment.
  • If the Relativistic Quark Model feed-down assumption is replaced by measured excited-state yields in the future, the absolute values of the fragmentation fractions may shift, but the pp versus p-Pb comparison would remain the cleanest probe of hadronisation modification.
  • A testable extension is to measure the Lambda_c+/D0 ratio in p-Pb in different centrality classes and correlate the position of the peak with the mean transverse momentum of light-flavour hadrons; a mass-dependent shift would confirm radial flow as the cause.
  • The system dependence of fragmentation fractions suggests that global event properties, such as final-state multiplicity, may be a better variable than collision system for organising charm-hadronisation measurements.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

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

Referee Report

2 major / 4 minor

Summary. This paper is a conference proceedings contribution on behalf of the ALICE Collaboration. It summarizes measurements of prompt D0, D+, D+s mesons and Lambda_c+ baryons at midrapidity in pp and p-Pb collisions at sqrt(s_NN) = 5.02 TeV, comparing the measured pT-differential ratios with several hadronisation models (PYTHIA 8 tunes, Catania, QCM, SHM with RQM feed-down). It then presents charm fragmentation fractions and the total charm production cross section per unit rapidity at midrapidity. The central claim is that the fragmentation fractions measured in pp and p-Pb collisions agree with each other, which the authors interpret as evidence that charm hadronisation is not modified from pp to p-Pb collisions. The paper also reports an apparent shift in the peak of the Lambda_c+/D0 ratio between the two systems.

Significance. If the central claim is correct, the result provides an important experimental constraint on models of charm hadronisation in nuclear collisions, particularly regarding whether cold nuclear matter effects or collective phenomena modify baryon-to-meson ratios. The paper's strength is that it rests on peer-reviewed ALICE measurements (refs. [1,2,15]); it gives a concise overview of a substantial body of data and model comparisons, including the first Lambda_c+/D0 measurement down to pT = 0 in p-Pb collisions. However, as a standalone article it does not contain the data tables or derivation steps needed to verify the central comparison, and one key comparison is not traceable to a cited source. The significance of the conclusion is therefore somewhat weakened by the missing documentation of the p-Pb fragmentation fractions.

major comments (2)
  1. [Section 3, left panel of Fig. 3] The central claim that "the charm fragmentation fractions measured in pp and p-Pb collisions agree with each other" is not supported by any cited source for the p-Pb fragmentation fractions. Unlike the other measurements, which cite refs. [1], [2], and [15], no reference or description is given for how the f(c -> H_c) values in p-Pb collisions were obtained. If the p-Pb sum in the right panel of Fig. 3 is normalized using pp values for species not measured in p-Pb (for example, Xi_c or Omega_c), the agreement is at least partly by construction. Please provide the reference for the p-Pb fragmentation fractions and state explicitly which charm-hadron species are measured in p-Pb at 5.02 TeV and how any unmeasured species are treated.
  2. [Section 3 and Fig. 3 right panel] Reference [17] is cited as the source of the NNLO predictions for the total charm production cross section, but ref. [17] (d'Enterria and Snigirev, "Triple parton scatterings in high-energy proton-proton collisions", Phys. Rev. Lett. 118, 122001 (2017)) does not contain NNLO predictions for charm production. The citation is mismatched, so the comparison with "NNLO [17]" in the text and figure cannot be checked. The authors should either cite the correct NNLO calculation for charm production at the LHC or reword the text to describe what ref. [17] actually provides.
minor comments (4)
  1. [Title and metadata] The manuscript contains repeated placeholder metadata such as "Journal Not Specified", "2023, 1, 0", and "Version December 31, 2024 submitted to Journal Not Specified"; these should be removed or replaced before submission.
  2. [References] References [15] and [19] are identical; they should be merged or renumbered.
  3. [Section 2, Fig. 2] The sentence "Within uncertainties, the Lambda_c+/D0 ratios agree between the two collision systems" would benefit from a quantitative compatibility statement (for example, a chi-square or p-value), because the qualitative wording does not convey the size of the uncertainties or the degree of agreement.
  4. [Section 2, Fig. 2 left panel] The caption of the left panel of Fig. 2 states the Lambda_c+/D0 ratio in pp collisions is compared with theoretical calculations, but the text does not identify which curves correspond to which model; please make the legend or caption self-contained.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the proceedings summarizes independent ALICE measurements with no in-paper derivation or fitted-parameter loop.

full rationale

This is a conference proceedings summary presenting previously published ALICE measurements, not a paper that derives a new result from fitted inputs. No parameter is fitted in the text, and no quantity is obtained from another quantity by construction. The central statement that the charm fragmentation fractions in pp and p–Pb collisions agree refers to measurements in references [1], [2], and [15], which are external data publications from the same collaboration but are independent experimental results rather than assumptions imported into this text. The Relativistic Quark Model feed-down appears only as one of several model predictions compared with the measured Λ_c+/D0 ratio, not as a data correction whose assumed value determines the reported fractions. The absence of a specific citation for the p–Pb fragmentation fractions is a referencing completeness concern, not a demonstrated circular reduction, because the paper describes those fractions as obtained by summing measured ground-state charm-hadron cross sections. Under the hard rule requiring an exhibited quotation showing that a result reduces to its own input, no such circular step can be identified. The paper’s reliance on earlier ALICE publications is normal self-citation that is not load-bearing for an in-paper derivation, since those cited papers contain the underlying measurements and not the conclusion being asserted here.

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

The contribution introduces no new parameters or entities. Its load-bearing premises are the factorization framework, the RQM-based feed-down model, and the completeness of the measured charm-hadron sum.

assumptions (3)
  • domain assumption Charm hadron production can be factorized into PDFs, partonic hard-scattering, and fragmentation functions that are universal across collision systems.
    The paper's comparison of fragmentation fractions assumes this standard QCD factorization framework (Section 1), while testing the universality part.
  • domain assumption The feed-down correction to Lambda_c+ from unmeasured excited charm baryon states follows the Relativistic Quark Model predictions.
    In Section 2, the model list states that SHM includes feed-down from RQM-predicted resonances; the measured Lambda_c+/D0 ratio therefore depends on this external model.
  • domain assumption Summing the measured ground-state charm hadron cross sections yields the total charm production cross section per unit rapidity.
    Section 3 computes dsigma_ccbar/dy from D0, D+, Ds+, Lambda_c+, and Xi_c plus charge conjugates; this requires that unmeasured species and excited states are negligible or corrected.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Charm production and hadronisation in pp and p--Pb collisions at $\sqrt{s_{\rm NN}} = $ 5.02 TeV at the LHC with ALICE." pith.science (2026). https://pith.science/paper/7NCKM2M6

@misc{pith2026241220939,
  author       = {Pith},
  title        = {Pith review of: Charm production and hadronisation in pp and p--Pb collisions at $\sqrts_\rm NN = $ 5.02 TeV at the LHC with ALICE},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/7NCKM2M6}},
  note         = {Machine review of arXiv:2412.20939}
}
abstract

Production measurements of charm hadrons, particularly the yield ratios of different hadron species as a function of the transverse momentum, are important to study the charm hadronisation mechanism. In this contribution, measurements of $\rm D^{0}$, $\rm D^{+}$, and $\rm D^{+}_{\rm s}$ meson production, as well as $\Lambda^{+}_{\rm c}$-baryon production at midrapidity in pp and p--Pb collisions at $\sqrt{s_{\rm NN}} = $ 5.02 TeV with ALICE will be discussed. The measurements will be compared with predictions from Monte Carlo event generators and theoretical calculations. In addition, the first baryon-to-meson yield ratio measurements for $\Lambda^{+}_{\rm c}/\rm D^{0}$ down to $p_{\rm T}$ = 0 in p--Pb collisions will be discussed. In such collisions, a modification of the hadronisation mechanisms could be present due to cold nuclear matter effects and possible collective phenomena. Finally, measurements of charm fragmentation fractions and the total charm production cross section per unit of rapidity at midrapidity, in pp and p--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at the LHC, will be presented.

Figures

Figures reproduced from arXiv: 2412.20939 by the authors.

Figure 1
Figure 1. Left: ratios between the pT-differential production cross section of D+ and D0 mesons [1]. Right: ratios between the D+ s -meson and the sum of the D0 - and D+-meson production cross sections. The ratios are compared with prediction obtained with FONLL calculations [7,8] using PYTHIA 8 [13,14] for the Hb → D + X decay kinematics. For the non-prompt D+ s /(D0 + D+) ratio, the predictions for the D+ s from B 0 s and f… view at source ↗
Figure 2
Figure 2. Left: the Λ+ c /D0 ratio as a function of pT measured in pp collisions at √ s = 5.02 TeV compared with theoretical calculations (see text for details). Right: prompt Λ+ c /D0 yield ratio in pp and p–Pb collisions as a function of pT, compared with QCM expectations [2]. between the D+ s mesons and the sum of the D+ and D0 can be calculated, as shown in the left and right panels of [PITH_FULL_IMAGE:figures/full_fig_p… view at source ↗
Figure 3
Figure 3. Left: charm-quark fragmentation fractions measured in pp and p–Pb collisions at √ sNN = 5.02 TeV compared with experimental measurements performed in e +e − collisions at LEP and B factories, and in e ±p at HERA [15,18]. Right: total charm production cross section at midrapidity per unit of rapidity as a function of the collision energy at the LHC [19,20] and RHIC [21] compared with FONLL [16] and NNLO calculations … view at source ↗

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

21 extracted references · 6 canonical work pages

  1. [17]

    Triple parton scatterings in high-energy proton-proton collisions

    d’Enterria, D.; Snigirev, A.M. Triple parton scatterings in high-energy proton-proton collisions. Phys. Rev. Lett. 2017, 118, 122001, [arXiv:hep-ph/1612.05582]. https://doi.org/10.1103/PhysRevLett.118.122001

    arXiv 2017

  2. [1]

    Measurement of beauty and charm production in pp collisions at √s = 5.02 TeV via non-prompt and prompt D mesons

    Acharya, S.; et al. Measurement of beauty and charm production in pp collisions at √s = 5.02 TeV via non-prompt and prompt D mesons. JHEP 2021, 05, 220, [arXiv:nucl-ex/2102.13601]. https://doi.org/10.1007/JHEP05(2021)220

    arXiv 2021

  3. [2]

    First measurement of Λc+ production down to pT=0 in pp and p-Pb collisions at sNN=5.02 TeV

    Acharya, S.; et al. First measurement of Λc+ production down to pT=0 in pp and p-Pb collisions at sNN=5.02 TeV. Phys. Rev. C 2023, 107, 064901, [arXiv:nucl-ex/2211.14032]. https://doi.org/10.1103/PhysRevC.107.064901

    arXiv 2023

  4. [3]

    Measurement of Prompt D 0, Λ+c , and Σ0,++ c (2455) Production in Proton–Proton Collisions at √s = 13 TeV

    Acharya, S.; et al. Measurement of Prompt D 0, Λ+c , and Σ0,++ c (2455) Production in Proton–Proton Collisions at √s = 13 TeV. Phys. Rev. Lett. 2022, 128, 012001, [arXiv:hep-ex/2106.08278]. https://doi.org/10.1103/PhysRevLett.128.012001

    arXiv 2022

  5. [4]

    Measurement of the cross sections of $\Xi^0_{\rm c}$ and $\Xi^+_{\rm c}$ baryons and branching-fraction ratio BR($\Xi^0_{\rm c} \rightarrow \Xi^-{\rm e}^+\nu_{\rm e}$)/BR($\Xi^0_{\rm c} \rightarrow \Xi^-\pi^+$) in pp collisions at 13 TeV

    Acharya, S.; et al. Measurement of the Cross Sections of Ξ0c and Ξ+c Baryons and of the Branching-Fraction Ratio BR( Ξ0c → Ξ−e+νe)/BR(Ξ0c → Ξ−π+) in pp collisions at 13 TeV. Phys. Rev. Lett. 2021, 127, 272001, [arXiv:nucl-ex/2105.05187]. https: //doi.org/10.1103/PhysRevLett.127.272001

    work page Pith review arXiv 2021

  6. [5]

    Measurement of the production cross section of prompt Ξ0c baryons at midrapidity in pp collisions at √s = 5.02 TeV

    Acharya, S.; et al. Measurement of the production cross section of prompt Ξ0c baryons at midrapidity in pp collisions at √s = 5.02 TeV. JHEP 2021, 10, 159, [arXiv:nucl-ex/2105.05616]. https://doi.org/10.1007/JHEP10(2021)159

    arXiv 2021

  7. [6]

    First measurement of $\rm \Omega_c^0$ production in pp collisions at $\sqrt{s}=13$ TeV

    Acharya, S.; et al. First measurement of Ωc0 production in pp collisions at s=13 TeV. Phys. Lett. B 2023, 846, 137625, [arXiv:nucl- ex/2205.13993]. https://doi.org/10.1016/j.physletb.2022.137625

    work page Pith review arXiv 2023

  8. [7]

    ThepT spectrum in heavy-flavour hadroproduction

    Cacciari, M.; Greco, M.; Nason, P . ThepT spectrum in heavy-flavour hadroproduction. JHEP 1998, 05, 007, [hep-ph/9803400]. https://doi.org/10.1088/1126-6708/1998/05/007

    arXiv 1998

Show all 21 references
  1. [8]

    The p(T) spectrum in heavy flavor photoproduction.JHEP 2001, 03, 006, [hep-ph/0102134]

    Cacciari, M.; Frixione, S.; Nason, P . The p(T) spectrum in heavy flavor photoproduction.JHEP 2001, 03, 006, [hep-ph/0102134]. https://doi.org/10.1088/1126-6708/2001/03/006

    2001 arXiv

  2. [9]

    Inclusive Charmed-Meson Production at the CERN LHC

    Kniehl, B.A.; Kramer, G.; Schienbein, I.; Spiesberger, H. Inclusive Charmed-Meson Production at the CERN LHC. Eur. Phys. J. C 2012, 72, 2082, [arXiv:hep-ph/1202.0439]. https://doi.org/10.1140/epjc/s10052-012-2082-2

    2012 arXiv

  3. [10]

    Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme

    Benzke, M.; Garzelli, M.V .; Kniehl, B.; Kramer, G.; Moch, S.; Sigl, G. Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme. JHEP 2017, 12, 021, [arXiv:hep-ph/1705.10386]. https://doi.org/10.1007/JHEP12(2017)021

    2017 arXiv

  4. [11]

    Study of heavy meson production in p–Pb collisions at √ S= 5.02 TeV in the general-mass variable- flavour-number scheme

    Kramer, G.; Spiesberger, H. Study of heavy meson production in p–Pb collisions at √ S= 5.02 TeV in the general-mass variable- flavour-number scheme. Nucl. Phys. B 2017, 925, 415–430, [arXiv:hep-ph/1703.04754]. https://doi.org/10.1016/j.nuclphysb.2017 .10.016

    2017 arXiv

  5. [12]

    Inclusive charmed-meson production from bottom hadron decays at the LHC.J

    Bolzoni, P .; Kramer, G. Inclusive charmed-meson production from bottom hadron decays at the LHC.J. Phys. G 2014, 41, 075006, [arXiv:hep-ph/1310.2924]. https://doi.org/10.1088/0954-3899/41/7/075006

    2014 arXiv

  6. [13]

    PYTHIA 6.4 Physics and Manual

    Sjostrand, T.; Mrenna, S.; Skands, P .Z. PYTHIA 6.4 Physics and Manual. JHEP 2006, 05, 026, [hep-ph/0603175]. https: //doi.org/10.1088/1126-6708/2006/05/026

    2006 arXiv

  7. [14]

    An introduction to PYTHIA 8.2

    Sjöstrand, T.; Ask, S.; Christiansen, J.R.; Corke, R.; Desai, N.; Ilten, P .; Mrenna, S.; Prestel, S.; Rasmussen, C.O.; Skands, P .Z. An introduction to PYTHIA 8.2. Comput. Phys. Commun. 2015, 191, 159–177, [arXiv:hep-ph/1410.3012]. https://doi.org/10.1016/j. cpc.2015.01.024

    2015 arXiv

  8. [16]

    Theoretical predictions for charm and bottom production at the LHC

    Cacciari, M.; Frixione, S.; Houdeau, N.; Mangano, M.L.; Nason, P .; Ridolfi, G. Theoretical predictions for charm and bottom production at the LHC. JHEP 2012, 10, 137, [arXiv:hep-ph/1205.6344]. https://doi.org/10.1007/JHEP10(2012)137

    2012 arXiv

  9. [18]

    Combined analysis of charm-quark fragmentation-fraction measurements

    Lisovyi, M.; Verbytskyi, A.; Zenaiev, O. Combined analysis of charm-quark fragmentation-fraction measurements. Eur. Phys. J. C 2016, 76, 397, [arXiv:hep-ex/1509.01061]. https://doi.org/10.1140/epjc/s10052-016-4246-y

    2016 arXiv

  10. [19]

    Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC

    Acharya, S.; et al. Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC. Phys. Rev. D 2022, 105, L011103, [arXiv:nucl-ex/2105.06335]. https://doi.org/10.1103/PhysRevD.105.L011103

    2022 arXiv

  11. [20]

    Measurement of charm production at central rapidity in proton-proton collisions at √s = 2.76 TeV

    Abelev, B.; et al. Measurement of charm production at central rapidity in proton-proton collisions at √s = 2.76 TeV. JHEP 2012, 07, 191, [arXiv:hep-ex/1205.4007]. https://doi.org/10.1007/JHEP07(2012)191

    2012 arXiv

  12. [21]

    Measurements of D0 and D∗ Production in p + p Collisions at √s = 200 GeV

    Adamczyk, L.; et al. Measurements of D0 and D∗ Production in p + p Collisions at √s = 200 GeV. Phys. Rev. D 2012, 86, 072013, [arXiv:nucl-ex/1204.4244]. https://doi.org/10.1103/PhysRevD.86.072013

    2012 arXiv

  13. [22]

    Upgrade of the ALICE Experiment: Letter Of Intent

    Abelev, B.; et al. Upgrade of the ALICE Experiment: Letter Of Intent. J. Phys. G 2014, 41, 087001. https://doi.org/10.1088/0954-3 899/41/8/087001

    2014 doi

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.