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Gluon Fragmentation into Heavy Quarkonium

High Energy Physics - Phenomenology · Submitted 2 Mar 1993 · 9 references

Pith's verdict: The founding fragmentation paper: the η_c derivation is clean and checkable, the ψ result is quoted without intermediate steps, and the erratum note in the revised version is not itemized.

T0 · AI review

How this review was made: An AI referee (selfhosted/deepseek-v4.1-flash) read the paper on November 13, 2026 and answered a fixed list of questions about it. T0 is the starting level every paper gets. The levels describe how deeply Pith has checked the paper, never the authors.

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  4. T3 Formal statement The claims written out in a formal math language a computer can read.
  5. T4 Proof Those claims proved, and the proof checked by computer.

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arXiv IDhep-ph/9303205 (version 1)
Pith ID2FOYCPC3, Pith's permanent record of this paper and its review
CitationEric Braaten, Tzu Chiang Yuan. "Gluon Fragmentation into Heavy Quarkonium." arXiv:hep-ph/9303205 (1993). https://pith.science/paper/2FOYCPC3
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Referee report
The paper

The paper claims

Gluon fragmentation into S-wave heavy quarkonium is computed to leading order in QCD, yielding explicit fragmentation functions for the eta_c and J/psi that are then evolved with Altarelli-Parisi equations.

The reading

When a proton collider produces a J/psi or an eta_c at very high transverse momentum, the usual picture is that the charm quark and antiquark are created directly in the hard collision. This paper argues that at high enough energy a different route dominates. A fast gluon is produced first, and that gluon then splits into the quarkonium state plus one or more ordinary partons. Because the splitting happens over a long time and a long distance (of order the inverse heavy-quark mass), the rate is enhanced by a factor of roughly (energy/mass)^2 relative to the direct process, which more than compensates for the extra power of the strong coupling it costs. The authors compute the probability distribution, called a fragmentation function, for a gluon to split into an eta_c and into a J/psi, working to leading order in the strong coupling. The eta_c case reduces to a compact closed-form expression. The J/psi case is a double integral whose integrand they write out explicitly. They then use the standard Altarelli-Parisi evolution equations to run these functions from the mass scale up to collider scales, summing the large logarithms of the scale ratio. Finally they estimate the transverse momentum at which fragmentation overtakes direct production, and argue it is low enough to matter for existing measurements. The key external input is the wavefunction of the bound state at the origin, taken from the measured leptonic width of the J/psi.
Extended reading notes

Core claim

The fragmentation functions D(z, mu) describing a gluon splitting into a heavy quarkonium state can be computed in perturbative QCD, and at high energy this fragmentation mechanism dominates quarkonium production because it is enhanced by (E/m_Q)^2. Concretely, Eq. (8) gives D_{g to eta_c}(z, 2m_c) in closed form, and Eqs. (9)-(15) give D_{g to psi}(z, 2m_c) as an explicit double integral, with Altarelli-Parisi evolution summing the logarithms of mu/m_Q at larger scales.

Load-bearing premise

The whole calculation rests on the nonrelativistic color-singlet model: the quarkonium is treated as a collinear c-cbar pair in a definite color-singlet spin state, with production amplitude proportional to the wavefunction at the origin R(0), and all binding and relativistic effects absorbed into that single number. This enters at Eq. (5), where the amplitude is written with the standard quarkonium Feynman rules of Ref. [3], and again where |R(0)|^2 = (0.8 GeV)^3 is fixed from the psi electronic width. If color-octet or relativistic contributions are comparable for S-wave states, the numerical fragmentation probabilities and the crossover estimates shift.

Original abstract

The dominant production mechanism for heavy quark-antiquark bound states in very high energy processes is fragmentation, the splitting of a high energy parton into a quarkonium state and other partons. We show that the fragmentation functions $D(z,\mu)$ describing these processes can be calculated using perturbative QCD. We calculate the fragmentation functions for a gluon to split into S-wave quarkonium states to leading order in the QCD coupling constant. The leading logarithms of $\mu/m_Q$, where $\mu$ is the factorization scale and $m_Q$ is the heavy quark mass, are summed up using Altarelli-Parisi evolution equations.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 3,651 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.21 · human participants 0.01 · controlled comparison 0.01 · randomized assignment 0.01 · states quantitative result 0.07 · compares with prior results 0.05 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

The dominant production mechanism for heavy quark-antiquark bound states in very high energy processes is fragmentation, the splitting of a high energy parton into a quarkonium state and other partons. We show that the fragmentation functions $D(z,\mu)$ describing these processes can be calculated using perturbative QCD. We calculate the fragmentation functions for a gluon to split into S-wave quarkonium states to leading order in the QCD coupling constant. The leading logarithms of $\mu/m_Q$, where $\mu$ is the factorization scale and $m_Q$ is the heavy quark mass, are summed up using Altarelli-Parisi evolution equations.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 The dominant production mechanism for heavy quark-antiquark bound states in very high energy processes is fragmentation, the splitting of a high energy parton into a quarkonium state and other partons. background 1.00 0.06 0.07 asserted 1.00
s1 We show that the fragmentation functions $D(z,\mu)$ describing these processes can be calculated using perturbative QCD. contribution 0.66 0.86 0.38 asserted 1.00
s2 We calculate the fragmentation functions for a gluon to split into S-wave quarkonium states to leading order in the QCD coupling constant. contribution 0.92 0.96 0.28 asserted 1.00
s3 The leading logarithms of $\mu/m_Q$, where $\mu$ is the factorization scale and $m_Q$ is the heavy quark mass, are summed up using Altarelli-Parisi evolution equations. method 0.93 0.76 0.17 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 0.99.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References
How the literature uses it

38 arXiv papers cite this in 62 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 44 sentences without a confident label

Contests it 1 paper
Builds on it 1 paper
Uses its method or tool 2 papers
Uses its data or values 1 paper
  • Results presented in this manuscript rely on the ZCW19$^+$ vector-quarkonium collinear NLO FF set, built in [ref] on the basis of initial-scale NRQCD inputs for constituent heavy-quark [ref] and gluon [ref] channels.

    Stabilizing BFKL via heavy-flavor and NRQCD fragmentation · Acknowledgments · 0.89

Compares with it 3 papers
Cites it as support 1 paper
Cites it as background 9 papers

Discussion

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