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REVIEW 2 major objections 5 minor 19 references

Jet Quenching in Heavy-Ion Collisions at RHIC and the LHC experiments

T0 review · 2 major / 5 minor · reviewed 2026-08-15 · deepseek-v4-flash

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Pith's one-line read Recent RHIC and LHC measurements together establish that jet suppression in the quark-gluon plasma depends on color charge, path length, and parton flavor, with acoplanarity as additional evidence.

desk verdict A clear, honest proceedings summary of published jet-quenching measurements; no new science, but a useful compact reference, with one notable citation gap for the ATLAS b-jet claim. read the letter →

arxiv 2505.04325 v1 pith:6F4CCGDX submitted 2025-05-07 nucl-ex hep-exhep-ph

Nihar Ranjan Sahoo This is my paper · ORCID
classification nucl-exhep-exhep-ph
keywords QuantumChromodynamicsQuark-GluonPlasmaJetquenchingheavy-ioncollisionspartonenergylossacoplanaritynuclearmodificationfactor
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

The paper assembles recent RHIC and LHC measurements of jet quenching into a single picture: high-energy partons crossing the quark-gluon plasma lose different amounts of energy depending on their color charge (gluons more than quarks), on how long a path they traverse, and on whether they are light or heavy. The key experimental facts are that inclusive jets are more suppressed than photon-tagged or b-tagged jets, that jet $v_1$ is an order of magnitude larger than the bulk flow, and that the ratio of jet yields at $R=0.2$ and $R=0.5$ falls below the pp baseline, indicating that lost energy is recovered at wider angles. The paper also reports evidence for jet acoplanarity: an enhancement of recoil-jet yields at large azimuthal separation from the trigger, seen in both STAR and ALICE. If these measurements are right, any viable model of jet-medium interaction must reproduce the color, path-length, and flavor dependence simultaneously. The paper frames these constraints, rather than new data, as the payoff: upcoming RHIC and LHC runs with better precision and wider kinematic reach will sharpen them.

What carries the argument

The central objects are semi-inclusive recoil-jet distributions selected by a high-$p_T$ trigger, either a direct photon, a neutral pion, or a hadron, with the underlying-event background subtracted by a mixed-event method (STAR) or a trigger-sampling method (ALICE). From these distributions the paper compares nuclear modification factors $I_{\mathrm{AA}}$ and $R_{\mathrm{AA}}$, the jet-resolution-parameter yield ratio $R=0.2/0.5$, the azimuthal anisotropy of jets $v_1$, and the acoplanarity distribution $I_{\mathrm{AA}}(\Delta\phi)$ as functions of recoil-jet $p_T$. The machinery works by separating the hard-scattered parton sample by its dominant flavor (photon tags quarks, pions and hadrons mix in more gluons) and by varying the cone radius to detect energy redistribution, while the $\Delta\phi$ distribution isolates the angular push of the medium.

What would settle it

A reanalysis of the STAR $\gamma$+jet and $\pi^0$+jet data at $\sqrt{s_{NN}}=200$ GeV with full systematic covariance, or a higher-statistics RHIC run, that found $I_{\mathrm{AA}}$ for the two triggers differ by more than the quoted uncertainties would settle whether the color-charge separation seen at the LHC is truly absent at RHIC; conversely, a new ATLAS or CMS measurement at 5.02 TeV with $p_T$-differential inclusive and $\gamma$-tagged jets showing identical suppression would refute the color-charge dependence.

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Extended reading notes

Core claim

On the paper's own terms, the central discovery is that jet suppression in heavy-ion collisions is not a single number but a structured pattern. At LHC energies, inclusive jets (mostly gluon-initiated) are suppressed more strongly than $\gamma$+jet pairs, which are mostly quark-initiated, while at RHIC the $\pi^0$+jet and $\gamma$+jet samples show comparable suppression within large uncertainties, a difference the paper attributes to similar quark fractions and limited precision. ATLAS finds b-jets roughly 20% less suppressed than inclusive jets, supporting mass-dependent energy loss. STAR's jet $v_1$ is an order of magnitude larger than the bulk $v_1$, implying strong path-length dependence tied to the tilted fireball geometry. Both STAR and ALICE see $R=0.2/0.5$ yield ratios below pp at intermediate $p_{T,\mathrm{jet}}$, evidence for intra-jet broadening beyond vacuum radiation, and the $I_{\mathrm{AA}}(\Delta\phi)$ distributions show yield enhancement at large angles, evidence for acoplanarity. The paper's conclusion is that these observations collectively constrain QGP opacity and coupling and challenge current models of in-medium radiation.

Load-bearing premise

The conclusions rest entirely on the accuracy of the cited published measurements, including their quoted uncertainties, background subtractions, and unfolding; if any of those results are misreported or incorrectly read, the corresponding jet-quenching claim would not stand.

Editorial extensions

If this is right

  • If the color-charge dependence is correct, gluon-initiated jets must always be suppressed more than quark-initiated jets at the same $p_T$, and models that treat all partons identically are ruled out.
  • If the $R=0.2/0.5$ yield ratio is truly below the pp baseline in heavy-ion collisions, the missing energy is not lost but redistributed to angles between $0.2$ and $0.5$, so wider-cone jets should recover the full yield at high enough $R$.
  • If the b-jet suppression deficit of about 20% holds, heavy-quark jets become a calibrated probe: their smaller energy loss sets the scale against which light-parton energy loss must be explained by color and mass effects.
  • If the jet $v_1$ result is right, jet quenching is sensitive to the initial-state geometry, meaning non-central collisions can be used to map the path-length dependence of energy loss differentially.
  • If the acoplanarity enhancement at large $\Delta\phi$ is confirmed by higher-statistics data, medium response (diffusion wake or quasi-particle scattering) must be included in jet observables, not only vacuum-like radiation.

Reading between the lines

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

  • The RHIC/LHC contrast suggests a testable threshold: a scan of trigger $p_T$ or collision energy should locate where the quark-gluon separation in $I_{\mathrm{AA}}$ emerges; the paper implies this is a precision effect, not a qualitative one.
  • If the high-$p_T$ rising trend in the $R=0.2/0.5$ ratio is caused by trigger-hadron energy loss, then a pure $\gamma$+jet measurement with high statistics should show a monotonic suppression without that rise, directly separating trigger energy loss from genuine broadening.
  • Bayesian extraction of transport coefficients could use the joint constraints of $I_{\mathrm{AA}}$, the $R=0.2/0.5$ ratio, and $v_1$ to break degeneracies that single-observable fits cannot resolve.
  • The large-angle enhancement seen by ALICE should be compared across collision systems (pA versus AA) to test whether the acoplanarity signal is specific to deconfined matter or scales with medium density.
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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 / 5 minor

Summary. This proceedings paper by N. R. Sahoo surveys recent jet-quenching measurements from RHIC (STAR) and the LHC (ALICE, ATLAS, CMS). It summarizes the experimental challenges in heavy-ion jet reconstruction, then discusses four manifestations of jet-medium interaction: suppression of jet yields and its dependence on the resolution parameter R, color-charge and path-length dependence of energy loss, intra-jet broadening, and jet acoplanarity. The manuscript is a review of already published or preliminary experimental results, and it explicitly declares that jet substructure and Bayesian extractions of transport properties are outside its scope.

Significance. If the cited measurements are correctly reported, the paper offers a compact, useful snapshot of the current experimental picture of jet quenching, drawing together STAR, ALICE, and ATLAS results. Its strengths are that it relies on peer-reviewed (or arXiv-posted) experimental papers, it includes several informative figures from those measurements, and it is honest about the limitations of a proceedings contribution. The main scientific risk is that the paper's central claim of parton-flavor dependence of energy loss rests on a quantitative b-jet suppression statement that is presented without any citable reference, and the path-length-dependence claim relies on a figure with no source citation. These gaps undermine verifiability of two of the four headline topics announced in the abstract.

major comments (2)
  1. [3.1] The sentence 'the R_AA measurement of b-jets compared to inclusive jets by ATLAS (shown at HP2024) shows that b-jets are approximately 20% less suppressed than inclusive jets' is a quantitative, load-bearing pillar of the paper's flavor-dependence conclusion (repeated in the abstract and in Section 4), but no reference is provided for it. The only ATLAS entry in the bibliography, Aad et al. (2023), compares inclusive and photon-tagged jets, not b-jets, and therefore cannot support the claim. Please either supply a citable ATLAS result for the b-jet R_AA (with the measured ratio, kinematics, and centrality range) or remove the b-jet statement and soften the abstract and Section 4 accordingly. As written, the reader cannot verify the 20% figure or its definition.
  2. [3.1 / Figure 4] The path-length-dependence claim in Section 4 is supported by the jet v1 measurement shown in Figure 4, with the text stating that the jet v1 is 'an order of magnitude larger than the bulk v1'. However, Figure 4 has no citation to the STAR measurement, and no reference is given for the bulk v1 curve or for the comparison. Please add the appropriate source (e.g., a STAR publication or conference proceedings) for the jet v1 data and a reference for the bulk v1, or explicitly mark the comparison as an unpublished preliminary observation. Without this, the path-length-dependence conclusion in the abstract is not independently checkable.
minor comments (5)
  1. [Abstract] The abstract contains grammar errors: 'Jet quenching serves as a key probes of the Quark-Gluon Plasma' should be 'a key probe', and 'Parton energy loss' should be 'parton energy loss'.
  2. [References] The bibliography entry 'Collab, S. (STAR), 2023' is an author-formatting artifact; the STAR Collaboration should be listed under 'STAR Collaboration' or under the collaboration's named authors. Also, the two STAR arXiv preprints, Aboona et al. (arXiv:2309.00156) and Collab (arXiv:2309.00145), should be cross-checked and cited with distinct, correctly formatted author lists and titles.
  3. [Figure 3] The caption 'Comparison between quark fraction between RHIC Collab (2023) and LHC energies' is awkward and should be revised, for example to 'Comparison of the quark-initiated jet fraction at RHIC and LHC energies'.
  4. [3.2] The text 'It is worth to not that the rising trend...' should read 'It is worth noting that the rising trend...'; similar typos elsewhere (e.g., 'particulalry', 'measurment', 'lenght') should be corrected throughout.
  5. [Figure 6] The bottom-left label '2 2.5 3' appears to be a leftover plot annotation from the source figure; remove or reposition it so the panel is clean.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the paper is a review of external measurements with no derivation chain; the uncited ATLAS b-jet claim is a verifiability gap, not circularity.

full rationale

This proceedings paper contains no derivation, fitting, or first-principles prediction. It summarizes externally published measurements from STAR, ALICE, and ATLAS and compares them with model calculations. The only self-citation is the author's own prior proceedings (Sahoo 2024), used as a reference for STAR highlights; none of the paper's summary claims depends on that citation as its load-bearing evidence. Claims about color-charge dependence, path-length dependence, jet-radius dependence, and acoplanarity are explicitly attributed to external data sets such as Aboona et al. (2023), Collab (2023), Acharya et al. (2024a,b), and Aad et al. (2023). There is no equation that redefines an input as an output, no fitted parameter relabeled as a prediction, and no uniqueness theorem imported from the authors' prior work. The unsupported statement in Sec. 3.1 that ATLAS (shown at HP2024) finds b-jets about 20% less suppressed than inclusive jets is an evidentiary and completeness concern because no reference is given, but it is not circularity: it points to an external measurement rather than deriving the claim from an input. The paper also explicitly states that some topics, such as jet substructure and Bayesian inference, are outside its scope, which does not affect circularity. Therefore the appropriate finding is no significant circularity.

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

This is a review paper; no new free parameters, no invented entities, and no new axioms beyond standard QCD and the accuracy of cited experimental results are introduced. The listed axioms are background assumptions needed for the summary's interpretive claims.

assumptions (3)
  • domain assumption The cited experimental results (STAR, ALICE, ATLAS) are accurately described.
    The entire content is a review of these measurements; no independent verification is provided. See Section 3 and Figures 2-6.
  • domain assumption Jet suppression and modification observables (R_AA, I_AA, v1, yield ratios) are valid signatures of parton energy loss in the QGP.
    Introduction and Section 3.1 treat these observables as direct evidence for energy loss, citing Adler et al. 2007, Adams et al. 2003, and Acharya et al. 2020/2022.
  • domain assumption Gluons lose more energy than quarks due to color Casimir factors (C_A=3 vs C_F=4/3).
    Section 3.1 uses this QCD relation to interpret differences in suppression between quark- and gluon-initiated jets.

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Cite this review

Pith. "Pith review of Jet Quenching in Heavy-Ion Collisions at RHIC and the LHC experiments." pith.science (2026). https://pith.science/paper/6F4CCGDX

@misc{pith2026250504325,
  author       = {Pith},
  title        = {Pith review of: Jet Quenching in Heavy-Ion Collisions at RHIC and the LHC experiments},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6F4CCGDX}},
  note         = {Machine review of arXiv:2505.04325}
}
read the original abstract

Jet quenching serves as a key probes of the Quark-Gluon Plasma (QGP) in heavy-ion collisions. This proceedings presents recent results from RHIC and LHC on jet energy loss, acoplanarity, and the flavour and path-length dependence of Parton energy loss, providing critical constraints on QGP properties and theoretical models. Upcoming data taking campaigns at RHIC and the LHC will offer enhanced precision and extended kinematic reach to further advance our understanding of jet-medium interactions.

Figures

Figures reproduced from arXiv: 2505.04325 by the authors.

Figure 1
Figure 1. Four manifestations of jet quenching in heavy-ion collisions. sample subtraction method Adam et al. (2015) in ALICE. The latter method effectively removes the multi-parton interactions in the jet sample. These approaches enable the measurment of semi-inclusive recoil jets down to relatively low transverse momentum (𝑝T,jet >≈ 5GeV/c) in heavy-ion collisions. On the other hand, experimental measurements are constraine… view at source ↗
Figure 2
Figure 2. 𝐼AA of 𝛾dir+jet and 𝜋 0+jet from the STAR experiment Aboona et al. (2023); Collab (2023). 𝑅AAof inclusive jet and 𝛾dir+jet Aad et al. (2023). N. R. Sahoo: Preprint submitted to Elsevier Page 2 of 6 [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Comparison between quark fraction between RHIC Collab (2023) and LHC energies. 3.1. Color factor and path length dependence of parton energy loss [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figures from the paper (3 more)
Figure 4
Figure 4. Figure 4: Jet 𝑣1 measured by the STAR experiment. Left: jet 𝑣1 vs. 𝜂, Right: d𝑣1/d𝜂 vs. 𝑝T . [GeV/c] ch T,jet p −1 10 1 0.2/0.5 ℜ STAR sNN=200 GeV +jet, Au+Au 0 Hybrid w/o wake,π Hybrid w/o wake,γ+jet, Au+Au +jet, Au+Au 0 Hybrid w/ wake, π Hybrid w/ wake,γ+jet, Au+Au Hybrid, p+p…
Figure 5
Figure 5. Figure 5: Yield ratios between R=0.2/0.5 for 𝛾dir+jet and 𝜋 0+jet from the STAR experiment Aboona et al. (2023); Collab (2023); hadron+jet measurement from ALICE Acharya et al. (2024a,b). 3.3. Medium induced jet acoplanarity in heavy-ion collisions Due to interactions with the m…
Figure 6
Figure 6. Figure 6: 𝐼AA as a function Δ𝜙 of 𝛾dir+jet and 𝜋 0+jet from the STAR Sahoo (2024) and ALICE Acharya et al. (2024a,b) experiment. suggest contributions from medium response effects, underscoring the need for further experimental investigation. A comprehensive understanding of col…

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Reference graph

Works this paper leans on

19 extracted references · 1 canonical work pages

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Reviewed August 15, 2026 · model on record in the stance chip above.