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arxiv: 2604.23189 · v1 · submitted 2026-04-25 · ✦ hep-ph

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Baryon enhancement in jets

Antonio Ortiz , Robert Vertesi
Authors on Pith no claims yet

Pith reviewed 2026-05-08 07:55 UTC · model grok-4.3

classification ✦ hep-ph
keywords baryon enhancementjetsproton-proton collisionsquark gluon jetsmultiplicity dependencePYTHIA8hadronization
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0 comments X

The pith

Baryon enhancement in high-pT jets from proton collisions arises from a shift to more gluon-initiated jets at higher multiplicity.

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

The paper examines why baryon production is enhanced relative to mesons in small collision systems, a result previously linked to quark-gluon plasma formation in heavy-ion collisions. Using PYTHIA8 simulations of proton-proton collisions at 13 TeV, it finds that jets above 15 GeV/c in transverse momentum exhibit this baryon enhancement that grows with jet multiplicity. The authors trace the trend to the changing balance between quark-initiated jets, which dominate at low multiplicity, and gluon-initiated jets, which dominate at high multiplicity. A sympathetic reader would care because the finding supplies a partonic explanation that does not invoke collective expansion or recombination in a medium, thereby offering a simpler account of the multiplicity dependence seen in data.

Core claim

In proton-proton collisions at 13 TeV simulated with PYTHIA8, a baryon enhancement is reported for charged jets with transverse momentum above 15 GeV/c. The enhancement increases with jet multiplicity and is explained by the transition from quark-initiated jets at low multiplicities to gluon-initiated jets at high multiplicities. This result challenges the interpretation that the multiplicity dependence of baryon enhancement requires collective expansion of the medium and quark recombination.

What carries the argument

The transition from quark-initiated jets to gluon-initiated jets with rising jet multiplicity.

If this is right

  • The multiplicity dependence of baryon-to-meson ratios inside jets can be reproduced without medium effects or collective flow.
  • Baryon enhancement trends in small systems may be reinterpreted as arising from the parton content of jets rather than recombination in a dense medium.
  • Quark-initiated jets and gluon-initiated jets must differ in their hadronization output for baryons if the multiplicity trend is to hold.
  • Alternative models that rely solely on collective expansion would overpredict the effect once the jet-initiator transition is included.

Where Pith is reading between the lines

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

  • The same quark-to-gluon transition could be checked directly by flavor-tagging jets in experimental data.
  • If the mechanism is general, it may also affect baryon ratios in other jet observables such as fragmentation functions or angular distributions.
  • Re-analysis of existing multiplicity-binned jet data with explicit separation of quark and gluon contributions would provide a direct test.

Load-bearing premise

The PYTHIA8 hadronization and parton-shower modeling accurately reproduces baryon production in jets in the absence of any collective effects.

What would settle it

Observation in real pp collision data of a baryon enhancement in high-pT jets that cannot be matched by PYTHIA8 or similar event generators when the quark versus gluon jet composition is accounted for would falsify the proposed explanation.

Figures

Figures reproduced from arXiv: 2604.23189 by Antonio Ortiz, Robert Vertesi.

Figure 1
Figure 1. Figure 1: FIG. 1. Baryon-to-meson ratios as a function of view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Proton-to-pion ratios as a function of view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Ratios of view at source ↗
read the original abstract

The enhancement of the baryon production relative to mesons in small-collision systems is considered a breakthrough result of the Large Hadron Collider since a similar effect in heavy-ion collisions is understood by invoking the formation of the strongly-interacting quark--gluon plasma. In this letter, a baryon enhancement is reported for $p_{\rm T}^{\rm ch,\, jet}>15$\,GeV/$c$ jets produced in pp collisions at $\sqrt{s}=13$\,TeV simulated with PYTHIA8. The effect can be explained as a transition between quark-initiated jets (low jet multiplicities) to gluon-initiated jets (high jet multiplicities). The present result challenges the interpretation about the multiplicity dependence of the baryon enhancement in terms of collective expansion of the medium and quark recombination.

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 / 1 minor

Summary. The manuscript reports a baryon-to-meson enhancement in charged jets with p_T^{ch,jet} > 15 GeV/c produced in pp collisions at √s = 13 TeV, as simulated with the publicly available PYTHIA8 Monte Carlo generator. The enhancement increases with jet multiplicity and is attributed to a transition from predominantly quark-initiated jets at low multiplicity to gluon-initiated jets at high multiplicity. The authors conclude that this conventional mechanism challenges experimental interpretations of similar multiplicity-dependent baryon enhancement in small systems in terms of collective expansion or quark recombination.

Significance. If the simulated trend were shown to quantitatively reproduce the experimental multiplicity dependence, the result would establish a viable baseline explanation rooted in standard parton-shower and hadronization modeling, reducing the necessity to invoke medium-like effects in pp collisions. The use of an unmodified, independent public generator is a strength, as it avoids circular parameter tuning to the target observable and allows direct reproducibility.

major comments (2)
  1. [Abstract] Abstract: The assertion that the result 'challenges the interpretation about the multiplicity dependence of the baryon enhancement in terms of collective expansion of the medium and quark recombination' is not supported by evidence. No quantitative comparison is presented between the simulated baryon-to-meson ratios (or their slopes versus multiplicity) and the corresponding ALICE or CMS measurements in pp collisions at 13 TeV for jets in the same p_T range.
  2. [Results] Results section: The explanation relies on the increasing gluon-jet fraction with multiplicity, yet the manuscript provides neither the separate multiplicity distributions for quark- versus gluon-initiated jets nor the baryon enhancement decomposed by jet origin. Without these, it is not demonstrated that the q/g transition fully accounts for the simulated enhancement.
minor comments (1)
  1. [Abstract] The abstract and conclusion would benefit from explicit statements of the jet reconstruction algorithm, charged-particle selection criteria, and multiplicity definition to allow direct replication.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment below and indicate the revisions we will make.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The assertion that the result 'challenges the interpretation about the multiplicity dependence of the baryon enhancement in terms of collective expansion of the medium and quark recombination' is not supported by evidence. No quantitative comparison is presented between the simulated baryon-to-meson ratios (or their slopes versus multiplicity) and the corresponding ALICE or CMS measurements in pp collisions at 13 TeV for jets in the same p_T range.

    Authors: We agree that no quantitative comparison to experimental data is presented and that this limits the strength of the claim as currently worded. The manuscript's core result is that a standard PYTHIA8 simulation without medium or recombination produces multiplicity-dependent baryon enhancement via the q-to-g jet transition. This establishes a viable conventional baseline that must be accounted for in data interpretations. To address the concern, we will revise the abstract to state that the result 'provides a conventional baseline explanation that challenges the necessity of invoking collective expansion or quark recombination' and will add a brief discussion of the lack of direct comparison as a limitation. revision: yes

  2. Referee: [Results] Results section: The explanation relies on the increasing gluon-jet fraction with multiplicity, yet the manuscript provides neither the separate multiplicity distributions for quark- versus gluon-initiated jets nor the baryon enhancement decomposed by jet origin. Without these, it is not demonstrated that the q/g transition fully accounts for the simulated enhancement.

    Authors: We agree that explicitly showing the multiplicity distributions separated by quark- versus gluon-initiated jets and the baryon-to-meson ratio decomposed by jet origin would strengthen the demonstration that the q/g transition accounts for the enhancement. We will add these as additional panels in an existing figure or a new figure in the revised Results section. revision: yes

Circularity Check

0 steps flagged

No circularity: direct output from independent PYTHIA8 simulation with no fitted parameters or self-referential derivation

full rationale

The paper reports a baryon-to-meson enhancement in high-multiplicity jets from running the publicly available PYTHIA8 Monte Carlo generator on pp collisions at 13 TeV. The claimed explanation (transition from quark-initiated jets at low multiplicity to gluon-initiated jets at high multiplicity) follows directly from tagging the initiating parton in the simulation truth record and binning the hadron ratios accordingly. No parameters are adjusted to match the target observable, no equations reduce the output to the input by construction, and the abstract contains no load-bearing self-citations or imported uniqueness theorems. The derivation chain is therefore a standard model exploration that remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of PYTHIA8's parton-shower and hadronization models plus the assumption that jet multiplicity serves as a reliable proxy for quark versus gluon initiation.

axioms (2)
  • domain assumption PYTHIA8 hadronization model accurately describes baryon production in jets
    The transition explanation depends on the generator's built-in fragmentation functions and string breaking parameters.
  • domain assumption Jet multiplicity directly indicates the initiating parton type without significant contamination from other processes
    Invoked when mapping low-multiplicity jets to quarks and high-multiplicity jets to gluons.

pith-pipeline@v0.9.0 · 5419 in / 1532 out tokens · 52493 ms · 2026-05-08T07:55:22.750071+00:00 · methodology

discussion (0)

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Reference graph

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