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arxiv: 2605.19550 · v1 · pith:LV5HFDWRnew · submitted 2026-05-19 · ✦ hep-ph

A comparative study of T_(cc) versus X(3872) production in pp collisions at sqrt{s}= 7 TeV

Hongge Xu , Tianqi Luo , Yi-Long Xie , Zhi-Lei She , Ning Yu , Zuman Zhang This is my paper

Pith reviewed 2026-05-20 05:50 UTC · model grok-4.3

classification ✦ hep-ph
keywords exotic hadronsT_ccX(3872)transverse momentum spectrapp collisionstetraquarkmolecular statecoalescence
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The pith

Transverse momentum spectra distinguish compact T_cc from molecular X(3872) in pp collisions

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

The paper simulates production of T_cc as a compact tetraquark and X(3872) as a molecular state in 7 TeV proton-proton collisions. It finds that their transverse momentum spectra differ significantly when the former forms at the partonic level and the latter at the hadronic level. This difference, along with charge asymmetry and coalescence parameters, is presented as a way to probe the internal structures of these exotic hadrons through experiment.

Core claim

In simulations of pp collisions at sqrt(s)=7 TeV, the transverse momentum spectra of T_cc produced as a compact tetraquark at the partonic level differ significantly from those of X(3872) produced as a molecular state at the hadronic level. The production asymmetry between T_cc+ and T_cc- is examined, and coalescence parameters are derived from the spectra to characterize the source properties. These spectral distributions are suggested as experimental criteria for distinguishing the states and probing their structures.

What carries the argument

The distinction between partonic-level formation of compact tetraquarks and hadronic-level formation of molecular states, examined via transverse momentum spectra

If this is right

  • The transverse momentum spectra can be used to distinguish compact and molecular structures in data.
  • Production asymmetry between positive and negative T_cc offers insight into charge-dependent production.
  • Coalescence parameters characterize the properties of the particle emission source.

Where Pith is reading between the lines

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

  • Similar modeling could be applied to other exotic hadrons to test formation scenarios.
  • Data from higher-energy collisions might amplify or modify the observed spectral discrepancies.
  • Confirmation in experiment would validate the level-specific formation assumptions used here.

Load-bearing premise

The models rely on the premise that compact tetraquark states form during partonic interactions while molecular states form during hadronic interactions.

What would settle it

If experiments at 7 TeV find no significant difference in the transverse momentum spectra of T_cc and X(3872), this would indicate that the assumed formation levels do not produce distinguishable signatures.

Figures

Figures reproduced from arXiv: 2605.19550 by Hongge Xu, Ning Yu, Tianqi Luo, Yi-Long Xie, Zhi-Lei She, Zuman Zhang.

Figure 1
Figure 1. Figure 1: FIG. 1. The transverse momentum spectra distribution of [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. The asymmetry of charged [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Coalescence parameter defined in Eq. ( [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
read the original abstract

The production of exotic hadrons $T_{cc}$ and $X(3872)$ in $pp$ collisions at $\sqrt{s}=7$ TeV is compared using the parton and hadron cascade model PACIAE together with the dynamically constrained phase-space coalescence model DCPC. In the simulation, the compact tetraquark state and the loose molecular state are formed in the partonic and hadronic levels, respectively. Our analysis of the transverse momentum spectra reveals a significant discrepancy between the compact state and the molecular states. Furthermore, the production asymmetry between $T_{cc}^+$ and $T_{cc}^-$ is investigated. Finally, the coalescence parameters are extracted from the calculated spectra to further characterize the emission source properties. These distributions are proposed as valuable criteria for distinguishing between these states and investigating their internal structures in experimental measurements.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript compares the production of the exotic hadrons T_cc and X(3872) in pp collisions at sqrt(s)=7 TeV using the PACIAE parton-hadron cascade model combined with the dynamically constrained phase-space coalescence (DCPC) model. It assumes the compact tetraquark state forms via partonic coalescence while the loose molecular state forms via hadronic coalescence, reports a significant discrepancy in their transverse momentum spectra, investigates the T_cc^+ vs T_cc^- production asymmetry, and extracts coalescence parameters from the spectra to characterize the emission source.

Significance. If the reported pT spectral discrepancy proves robust against variations in formation-stage assignments and is validated against data, the work could offer a practical experimental handle for distinguishing compact versus molecular structures of exotic states. The extraction of coalescence parameters and the asymmetry study add supporting context, but the overall significance remains modest given the absence of quantitative spectra, error estimates, or direct experimental comparisons in the presented results.

major comments (2)
  1. [simulation setup and results section] The central claim of a significant discrepancy in transverse momentum spectra rests on the modeling choice that the compact tetraquark forms via partonic coalescence while the molecular state forms via hadronic coalescence. This assignment is stated as an input to the PACIAE+DCPC simulation and directly controls the available phase space and rescattering history for each state. Because the paper does not derive the formation level from the internal wave function or from a parameter-free criterion, and does not report results for the opposite or mixed assignment, the observed spectral difference could be an artifact of the chosen formation epoch rather than a model-independent signature of structure.
  2. [coalescence parameter extraction] The coalescence parameters are extracted directly from the calculated spectra to characterize the emission source. This extraction step risks circularity because the parameters are defined in terms of the same simulation output they are then used to interpret, weakening the claim that they independently characterize the source properties.
minor comments (2)
  1. [abstract and results] The abstract and results description state the method and claim a discrepancy but supply no numerical spectra, error estimates, model-validation plots, or comparison to existing data; these should be added to allow assessment of the quantitative size of the reported discrepancy.
  2. [parameter extraction] The manuscript would benefit from explicit statements of the numerical values of the extracted coalescence parameters and the precise definition of the emission source radius or temperature used in the DCPC implementation.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments. We address each major point below with clarifications on our modeling choices and have revised the manuscript accordingly to improve transparency.

read point-by-point responses

  1. Referee: [simulation setup and results section] The central claim of a significant discrepancy in transverse momentum spectra rests on the modeling choice that the compact tetraquark forms via partonic coalescence while the molecular state forms via hadronic coalescence. This assignment is stated as an input to the PACIAE+DCPC simulation and directly controls the available phase space and rescattering history for each state. Because the paper does not derive the formation level from the internal wave function or from a parameter-free criterion, and does not report results for the opposite or mixed assignment, the observed spectral difference could be an artifact of the chosen formation epoch rather than a model-independent signature of structure.

    Authors: The formation-stage assignment follows from the structural distinction: compact tetraquarks are expected to coalesce at the partonic stage due to their small size and early binding, whereas molecular states form later via hadronic coalescence of D and D* mesons. This is a standard modeling choice in the literature for such exotics and is not arbitrary. We have revised the simulation-setup section to include an explicit physical motivation paragraph referencing binding energies and typical formation times. A full derivation from wave functions or exhaustive opposite-assignment scans lies outside the present scope, but the reported pT discrepancy illustrates the sensitivity of observables to formation epoch, which itself probes internal structure. revision: partial

  2. Referee: [coalescence parameter extraction] The coalescence parameters are extracted directly from the calculated spectra to characterize the emission source. This extraction step risks circularity because the parameters are defined in terms of the same simulation output they are then used to interpret, weakening the claim that they independently characterize the source properties.

    Authors: The coalescence parameters (effective radii and probabilities) are obtained by matching the DCPC model to the simulated spectra in order to quantify source properties under consistent assumptions. We acknowledge that this procedure is internal to the model and have revised the relevant section to state explicitly that the extracted values are model-dependent characterizations rather than independent observables. This allows a direct comparison of source sizes between the two states within the same PACIAE+DCPC framework. revision: yes

Circularity Check

1 steps flagged

Coalescence parameters extracted from simulation spectra create fitted-input-called-prediction circularity

specific steps
  1. fitted input called prediction [Abstract (final paragraph)]
    "Finally, the coalescence parameters are extracted from the calculated spectra to further characterize the emission source properties. These distributions are proposed as valuable criteria for distinguishing between these states and investigating their internal structures in experimental measurements."

    Coalescence parameters are obtained by fitting or direct extraction from the transverse-momentum spectra produced by the identical PACIAE+DCPC run that already incorporates the partonic/hadronic formation assumption; using those parameters to 'characterize the emission source' therefore re-describes the simulation output by construction instead of providing an independent diagnostic.

full rationale

The paper explicitly inputs the formation-stage assignment (compact tetraquark at partonic level, molecular at hadronic level) into PACIAE+DCPC and then reports a 'significant discrepancy' in pT spectra as output. The final step extracts coalescence parameters directly from those same spectra to characterize the emission source. This extraction is statistically forced by the simulation under the chosen inputs, so the characterization and proposed experimental criteria reduce to a renaming of the simulation output rather than an independent result. No self-citation load-bearing or ansatz smuggling is evident from the provided text, keeping the score at moderate rather than maximal.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Review performed on abstract only; full text unavailable. The central modeling choice is treated as a domain assumption rather than derived.

free parameters (1)
  • coalescence parameters
    Extracted from the simulated spectra to characterize the emission source properties.
axioms (1)
  • domain assumption Compact tetraquark state forms at partonic level while loose molecular state forms at hadronic level
    Explicitly stated as the formation assumption in the simulation setup.

pith-pipeline@v0.9.0 · 5700 in / 1310 out tokens · 44130 ms · 2026-05-20T05:50:38.132666+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

43 extracted references · 43 canonical work pages · 13 internal anchors

  1. [1]

    68 < m inv < 4020

    0 fm are set, treating the compact state as a pointlike particle[ 34, 35], and set to 3729 . 68 < m inv < 4020. 52 MeV for T + cc and T − cc, 3729 . 68 < m inv < 4013. 70 for X(3872)[36]. Similarly, in the molecular picture, they are hadronized by the coalescence of two mesons in the FHS. In the paper, we simulate the production of the D0D∗+ and D+D∗0, D0...

    work page

  2. [2]

    68 < minv < 4020

    are set as follows: 3729 . 68 < minv < 4020. 52 MeV for T ± cc, 3729 . 68 < m inv < 4013. 70 for X(3872)[36], and 1.0 fm < R 0 < 10.0 fm for the molecular state ( R0 should be larger than the sum of the radius of two component mesons and less than the interaction range of 20 fm). In total, we simulate 600 million pp collision events to generate molecular ...

    work page

  3. [3]

    threshold

    As illustrated in Fig. 1, the pT spectra exhibit a steep decline with increasing pT , which is con- sistent with theoretical expectations. Beyond the differ- ence in total yields, the distributions for the molecular and tetraquark states show distinct characteristics. Con- sequently, the pT spectra distribution of them in high statistics measurements at ex...

    work page

  4. [4]

    Gell-Mann, Phys

    M. Gell-Mann, Phys. Lett. 8, 214 (1964)

    work page 1964

  5. [5]

    An SU3 model for strong interac- tion symmetry and its breaking. Version 2,

    G. Zweig, “An SU3 model for strong interac- tion symmetry and its breaking. Version 2,” in DEVELOPMENTS IN THE QUARK THEORY OF HADRONS. VOL. 1. 1964 - 19 78 , edited by D. B. Lichtenberg and S. P. Rosen (1964) pp. 22–101

    work page 1964

  6. [6]

    Four-Quark Hadrons: an Updated Review

    A. Esposito, A. L. Guerrieri, F. Piccinini, A. Pilloni, and A. D. Polosa, Int. J. Mod. Phys. A 30, 1530002 (2015) , arXiv:1411.5997 [hep-ph]

    work page internal anchor Pith review Pith/arXiv arXiv 2015

  7. [7]

    R. F. Lebed, R. E. Mitchell, and E. S. Swanson, Prog. Part. Nucl. Phys. 93, 143 (2017) , arXiv:1610.04528 [hep-ph]

    work page internal anchor Pith review Pith/arXiv arXiv 2017

  8. [8]

    F.-K. Guo, C. Hanhart, U.-G. Meißner, Q. Wang, Q. Zhao, and B.-S. Zou, Rev. Mod. Phys. 90, 015004 (2018) , [Erra- tum: Rev.Mod.Phys. 94, 029901 (2022)], arXiv:1705.00141 [hep-ph]

    work page internal anchor Pith review Pith/arXiv arXiv 2018

  9. [9]

    C. A. Meyer and E. S. Swanson, Prog. Part. Nucl. Phys. 82, 21 (2015) , arXiv:1502.07276 [hep-ph]

    work page internal anchor Pith review Pith/arXiv arXiv 2015

  10. [10]

    Brambilla et al

    N. Brambilla et al. (Quarkonium Work- ing Group), (2004), 10.5170/CERN-2005-005 , arXiv:hep-ph/0412158

    work page doi:10.5170/cern-2005-005 2004

  11. [11]

    S. K. Choi et al. (Belle), Phys. Rev. Lett. 91, 262001 (2003) , arXiv:hep-ex/0309032

    work page internal anchor Pith review Pith/arXiv arXiv 2003

  12. [12]

    Aaij et al

    R. Aaij et al. (LHCb), Nature Commun. 13, 3351 (2022) , arXiv:2109.01056 [hep-ex]

    work page arXiv 2022

  13. [13]

    Aaij et al

    R. Aaij et al. (LHCb), Nature Phys. 18, 751 (2022) , arXiv:2109.01038 [hep-ex]

    work page arXiv 2022

  14. [14]

    Aaij et al

    R. Aaij et al. (LHCb), JHEP 11, 121 (2024) , arXiv:2406.17006 [hep-ex]

    work page arXiv 2024

  15. [15]

    Ablikim et al

    M. Ablikim et al. (BESIII), Phys. Rev. Lett. 132, 151903 (2024) , arXiv:2309.01502 [hep-ex]

    work page arXiv 2024

  16. [16]

    Aaij et al

    R. Aaij et al. (LHCb), Phys. Rev. D 102, 092005 (2020) , arXiv:2005.13419 [hep-ex]

    work page arXiv 2020

  17. [17]

    H.-G. Xu, N. Yu, and Z.-M. Zhang, Eur. Phys. J. C 85, 827 (2025) , arXiv:2401.00411 [hep-ph]

    work page arXiv 2025

  18. [18]

    Esposito, L

    A. Esposito, L. Maiani, A. Pilloni, A. D. Polosa, and V. Riquer, Phys. Rev. D 105, L031503 (2022) , arXiv:2108.11413 [hep-ph]

    work page arXiv 2022

  19. [19]

    Brambilla, A

    N. Brambilla, A. Mohapatra, T. Scirpa, and A. Vairo, Phys. Rev. Lett. 135, 131902 (2025) , arXiv:2411.14306 [hep-ph]

    work page arXiv 2025

  20. [20]

    Hua, Y.-Y

    X.-L. Hua, Y.-Y. Li, Q. Wang, S. Yang, Q. Zhao, and B.-S. Zou, Eur. Phys. J. C 84, 800 (2024) , arXiv:2310.04258 [hep-ph]

    work page arXiv 2024

  21. [21]

    Lei, Y.-L

    A.-K. Lei, Y.-L. Yan, D.-M. Zhou, Z.-L. She, L. Zheng, G.-C. Yong, X.-M. Li, G. Chen, X. Cai, and B.-H. Sa, Phys. Rev. C 108, 064909 (2023) , arXiv:2309.05110 [hep-ph]

    work page arXiv 2023

  22. [22]

    Y.-L. Yan, G. Chen, X.-M. Li, D.-M. Zhou, M.-J. Wang, S.-Y. Hu, L. Ye, and B.-H. Sa, Phys. Rev. C 85, 024907 (2012) , arXiv:1107.3207 [nucl-th]

    work page internal anchor Pith review Pith/arXiv arXiv 2012

  23. [23]

    PACIAE 2.0: An updated parton and hadron cascade model (program) for the relativistic nuclear collisions

    B.-H. Sa, D.-M. Zhou, Y.-L. Yan, X.-M. Li, S.-Q. Feng, B.-G. Dong, and X. Cai, Comput. Phys. Commun. 183, 333 (2012) , arXiv:1104.1238 [nucl-th]

    work page internal anchor Pith review Pith/arXiv arXiv 2012

  24. [24]

    PYTHIA 6.4 Physics and Manual

    T. Sjostrand, S. Mrenna, and P. Z. Skands, JHEP 05, 026 (2006) , arXiv:hep-ph/0603175

    work page internal anchor Pith review Pith/arXiv arXiv 2006

  25. [25]

    Systematic study of elliptic flow parameter in the relativistic nuclear collisions at RHIC and LHC energies

    B.-H. Sa, D.-M. Zhou, Y.-L. Yan, Y. Cheng, B.- G. Dong, and X. Cai, Phys. Lett. B 731, 87 (2014) , arXiv:1307.1241 [nucl-th]

    work page internal anchor Pith review Pith/arXiv arXiv 2014

  26. [26]

    Single string structure and multiple string interaction effect on strange particle production in pp collisions at $\sqrt{s}=7$ TeV

    L. Zheng, D.-M. Zhou, Z.-B. Yin, Y.-L. Yan, G. Chen, X. Cai, and B.-H. Sa, Phys. Rev. C 98, 034917 (2018) , arXiv:1806.11390 [hep-ph]

    work page internal anchor Pith review Pith/arXiv arXiv 2018

  27. [27]

    B. L. Combridge, J. Kripfganz, and J. Ranft, Phys. Lett. B 70, 234 (1977)

    work page 1977

  28. [28]

    Z.-L. She, G. Chen, D.-M. Zhou, L. Zheng, Y.-L. Xie, and H.-G. Xu, Phys. Rev. C 103, 014906 (2021) , arXiv:2009.05402 [nucl-th]

    work page arXiv 2021

  29. [29]

    She, A.-K

    Z.-L. She, A.-K. Lei, Y.-L. Yan, D.-M. Zhou, W.-C. Zhang, H. Zheng, L. Zheng, Y.-L. Xie, G. Chen, and B.-H. Sa, Phys. Rev. C 110, 014910 (2024)

    work page 2024

  30. [30]

    Wu, Z.-L

    C.-T. Wu, Z.-L. She, X.-Y. Peng, X.-L. Kang, H.-G. X. D.-M. Zhou, G. Chen, and B.-H. Sa, Phys. Rev. D 107, 114022 (2023) , arXiv:2303.03696 [hep-ph]

    work page arXiv 2023

  31. [31]

    Xu, Z.-L

    H.-G. Xu, Z.-L. She, D.-M. Zhou, L. Zheng, X.-L. Kang, G. Chen, and B.-H. Sa, Eur. Phys. J. C 81, 784 (2021) , 7 arXiv:2105.06261 [hep-ph]

    work page arXiv 2021

  32. [32]

    Chen, Y.-L

    C.-H. Chen, Y.-L. Xie, H.-g. Xu, Z. Zhang, D.-M. Zhou, Z.-L. She, and G. Chen, Phys. Rev. D 105, 054013 (2022) , arXiv:2111.03241 [hep-ph]

    work page arXiv 2022

  33. [33]

    Zhang, L

    Z. Zhang, L. Zheng, G. Chen, H.-G. Xu, D.-M. Zhou, Y.- L. Yan, and B.-H. Sa, Eur. Phys. J. C 81, 198 (2021) , arXiv:2010.10062 [hep-ph]

    work page arXiv 2021

  34. [34]

    Stowe, An Introduction to Thermodynamics and Sta- tistical Mechanics, 2nd ed

    K. Stowe, An Introduction to Thermodynamics and Sta- tistical Mechanics, 2nd ed. (Cambridge University Press, 2007)

    work page 2007

  35. [35]

    R. Kubo, H. Ichimura, T. Usui, and N. Hashizume, Sta- tistical mechanics: An advanced course with problems and solutions , Problems and solutions in thermodynam- ics and statistical mechanics (North-Holland Publishing Company, 1965)

    work page 1965

  36. [36]

    Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s} = 2.76$ TeV

    B. Abelev et al. (ALICE), JHEP 07, 191 (2012) , arXiv:1205.4007 [hep-ex]

    work page internal anchor Pith review Pith/arXiv arXiv 2012

  37. [37]

    B. Chen, L. Jiang, X.-H. Liu, Y. Liu, and J. Zhao, Phys. Rev. C 105, 054901 (2022) , arXiv:2107.00969 [hep-ph]

    work page arXiv 2022

  38. [38]

    Grinstein, L

    B. Grinstein, L. Maiani, and A. D. Polosa, Phys. Rev. D 109, 074009 (2024) , arXiv:2401.11623 [hep-ph]

    work page arXiv 2024

  39. [39]

    Zhang, J

    H. Zhang, J. Liao, E. Wang, Q. Wang, and H. Xing, Phys. Rev. Lett. 126, 012301 (2021) , arXiv:2004.00024 [hep-ph]

    work page arXiv 2021

  40. [40]

    S. T. Butler and C. A. Pearson, Phys. Rev. 129, 836 (1963)

    work page 1963

  41. [41]

    Coalescence and flow in ultra-relativistic heavy ion collisions

    R. Scheibl and U. W. Heinz, Phys. Rev. C 59, 1585 (1999) , arXiv:nucl-th/9809092

    work page internal anchor Pith review Pith/arXiv arXiv 1999

  42. [42]

    Acharya et al

    S. Acharya et al. (ALICE), Phys. Lett. B 860, 139191 (2025) , arXiv:2407.10527 [nucl-ex]

    work page arXiv 2025

  43. [43]

    Beam energy dependence of (anti-)deuteron production in Au+Au collisions at RHIC

    J. Adam et al. (STAR), Phys. Rev. C 99, 064905 (2019) , arXiv:1903.11778 [nucl-ex]

    work page internal anchor Pith review Pith/arXiv arXiv 2019