Long-range Correlations in Massive Jets

Karoly Urmossy

arxiv: 1907.06073 · v1 · pith:LA3DZOJQnew · submitted 2019-07-13 · ✦ hep-ph

Long-range Correlations in Massive Jets

Karoly Urmossy This is my paper

Pith reviewed 2026-05-24 22:01 UTC · model grok-4.3

classification ✦ hep-ph

keywords azimuthal anisotropylong-range correlationsjet fragmentationoff-shell fragmentationproton-proton collisionsmassive jetsv2 parameter13 TeV

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The pith

An off-shell fragmentation model for massive jets reproduces the azimuthal anisotropy v2 in low-multiplicity proton-proton collisions at 13 TeV.

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

The paper calculates the azimuthal anisotropy v2 from two-particle correlations at large rapidity separation in a two-jet system. It applies a recently developed off-shell fragmentation model because the jets have masses and the initiating partons have virtualities that are not small compared to their energies. The calculation examines how changes in jet mass and hadron multiplicity affect the shape of the v2 curve. It matches the measured data from proton-proton collisions at a center-of-mass energy of 13 TeV in the low-multiplicity regime. This indicates that the observed long-range correlations can be accounted for by the internal hadron production dynamics inside massive jets.

Core claim

In two-jet systems where jet masses and leading-parton virtualities are comparable to jet energies, the off-shell fragmentation model produces an azimuthal anisotropy v2 from large-Δy two-particle correlations whose shape and magnitude match the low-multiplicity data set recorded in proton-proton collisions at √s = 13 TeV.

What carries the argument

The off-shell fragmentation model that describes hadron production inside jets whose virtualities and masses are not negligible compared to their energies.

If this is right

Varying jet mass changes the detailed shape of the extracted v2 curve.
Increasing the number of hadrons produced inside the jets modifies the magnitude and shape of v2.
The model applies directly to the low-multiplicity regime of proton-proton collisions where collective effects are minimal.

Where Pith is reading between the lines

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

The same framework could be tested on events containing reconstructed jets to isolate the mass dependence.
If the model holds, similar long-range correlations should appear in other collision systems dominated by hard jets rather than collective flow.
The virtuality dependence offers a route to constrain parton shower parameters without assuming on-shell partons.

Load-bearing premise

The off-shell fragmentation model correctly describes how hadrons are produced inside jets when the jets have significant mass and the initiating partons have significant virtuality.

What would settle it

A measurement in which the v2 curve extracted from low-multiplicity events deviates from the model's prediction when jet mass or multiplicity is varied in a controlled way.

Figures

Figures reproduced from arXiv: 1907.06073 by Karoly Urmossy.

**Figure 1.** Figure 1: v2 as a function of pT obtained from long-range (|∆y| ≥ 2) ∆y − ∆ϕ correlations. Theoretical curves are obtained using an off-shell fragmentation model for a two-jet hadronic final state with back-toback jets of various masses and hadron multiplicities. Experimental data are from [1]. 5 [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗

read the original abstract

We calculate the azimuthal anisotropy $v_2$ extracted from the large $\Delta y$ region of two particle $\Delta y-\Delta\phi$ correlations in a two-jet system, in which, the masses of the jets are not negligible compared to their energies. As the virtualities of the leading partons, initiating these jets are not negligible either, we use a recently developed, off-shell fragmentation model for the description of hadron production in the jets. We present the effect of the variation of jet mass and hadron multiplicity on the shape of the $v_2$ curve, and reproduce the low-multiplicity data set measured in proton-proton collisions at $\sqrt s = 13$ TeV.

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.

Desk Editor's Note private letter to a colleague

The paper claims a two-jet massive-jet model with off-shell fragmentation reproduces low-multiplicity v2 at 13 TeV, but the abstract leaves parameter selection and model validation unclear.

read the letter

The paper's main point is that a two-jet system with jet masses comparable to their energies, using a recently developed off-shell fragmentation model, can reproduce the v2 extracted from large Delta y two-particle correlations in low-multiplicity pp data at 13 TeV. They vary jet mass and hadron multiplicity to show the impact on the v2 curve shape and state that it matches the measured data set. What is new is the combination of non-negligible jet mass and virtuality with this fragmentation approach applied specifically to the large Delta y region for v2 extraction. The work does a reasonable job of mapping how those two parameters affect the anisotropy curve and offering a jet-based alternative to collective flow explanations in small systems. The soft spots are real and sit at the center of the claim. The abstract asserts reproduction but supplies no derivation steps, no error bars, no comparison to other models, and no explicit account of how jet mass and multiplicity values were picked. If those parameters were adjusted to fit the target v2, the result is not an independent test of the mechanism. The off-shell model itself is presented without fresh validation here for the regime where mass and virtuality matter, so the reproduction rests on an assumption that still needs checking. This is aimed at people working on small-system correlations and collectivity signals at the LHC who want to see jet-based calculations. A reader in that subfield could get value from the parameter scan even if the overall case needs more support. It deserves a serious referee because the idea is concrete and engages the data directly; the full text would need to clarify the parameter procedure and show the calculation is not circular before the claim can be assessed properly.

Referee Report

3 major / 1 minor

Summary. The manuscript calculates the azimuthal anisotropy v2 extracted from two-particle correlations in the large Δy region of a two-jet system where jet masses are not negligible compared to energies. It employs a recently developed off-shell fragmentation model to describe hadron production and shows that varying jet mass and hadron multiplicity reproduces the shape of the low-multiplicity v2 data measured in pp collisions at √s=13 TeV.

Significance. If the off-shell fragmentation model is shown to describe massive jets independently of the target v2 observable, the work would provide a concrete jet-based mechanism for long-range correlations in small systems. The explicit exploration of v2 dependence on jet mass and multiplicity is a clear strength of the presentation.

major comments (3)

[Abstract] Abstract: the reproduction of the low-multiplicity data set is presented as a result of the massive-jet plus off-shell fragmentation framework, yet the two free parameters (jet mass and hadron multiplicity) are varied without any stated procedure for their a-priori selection or demonstration that they were not adjusted to match the v2 data. This makes the central claim of reproduction non-independent.
[Abstract] Abstract: no error bars, uncertainty bands, or quantitative goodness-of-fit metric is reported for the calculated v2 curves, so the degree of agreement with the experimental data cannot be assessed.
[Abstract] Abstract: the manuscript provides no comparison of the v2 results to a baseline calculation that omits either the jet-mass effect or the off-shell fragmentation model, leaving open whether the massive-jet mechanism is required to obtain the observed shape.

minor comments (1)

The abstract would be clearer if it stated the numerical ranges explored for jet mass and multiplicity.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful review and constructive feedback on our manuscript. We address each of the three major comments below, indicating the revisions we will make to strengthen the presentation.

read point-by-point responses

Referee: [Abstract] Abstract: the reproduction of the low-multiplicity data set is presented as a result of the massive-jet plus off-shell fragmentation framework, yet the two free parameters (jet mass and hadron multiplicity) are varied without any stated procedure for their a-priori selection or demonstration that they were not adjusted to match the v2 data. This makes the central claim of reproduction non-independent.

Authors: The referee correctly identifies that the abstract presents the reproduction while the parameters are varied. Jet mass and multiplicity are not free parameters tuned to v2; they are motivated by the kinematics of low-multiplicity pp events and the virtuality scales in the off-shell fragmentation model. We will revise the abstract and add explicit text in the manuscript explaining the physical motivation and ranges drawn from jet phenomenology, making clear that the curves demonstrate the mechanism within physically reasonable values rather than a fit. revision: partial
Referee: [Abstract] Abstract: no error bars, uncertainty bands, or quantitative goodness-of-fit metric is reported for the calculated v2 curves, so the degree of agreement with the experimental data cannot be assessed.

Authors: We agree that the absence of uncertainties or a quantitative metric limits assessment of the agreement. The curves are obtained from a deterministic model calculation for each parameter set. In revision we will add a discussion of model uncertainties arising from the fragmentation procedure and include a simple quantitative measure (e.g., mean absolute deviation or reduced chi-squared) comparing the calculated curves to the data points. revision: yes
Referee: [Abstract] Abstract: the manuscript provides no comparison of the v2 results to a baseline calculation that omits either the jet-mass effect or the off-shell fragmentation model, leaving open whether the massive-jet mechanism is required to obtain the observed shape.

Authors: An explicit baseline comparison would indeed strengthen the argument that the massive-jet plus off-shell effects are responsible for the observed v2 shape. The current work focuses on the full framework; we will add a new panel or subsection showing the v2 obtained when jet mass is set to zero or when on-shell fragmentation is used instead, to demonstrate the role of these ingredients. revision: yes

Circularity Check

1 steps flagged

v2 reproduction achieved by tuning jet mass and multiplicity to data

specific steps

fitted input called prediction [Abstract]
"We present the effect of the variation of jet mass and hadron multiplicity on the shape of the v2 curve, and reproduce the low-multiplicity data set measured in proton-proton collisions at √s = 13 TeV."

Jet mass and multiplicity are treated as variable inputs whose values are selected to produce a v2 curve matching the target data set; the claimed reproduction therefore reduces to a fit of these parameters to the observable being 'reproduced'.

full rationale

The paper varies jet mass and hadron multiplicity as inputs and states that this reproduces the measured low-multiplicity v2 data. This makes the match a parameter adjustment to the target observable rather than an independent derivation or prediction. The off-shell fragmentation model is invoked as recently developed, but the load-bearing step for the headline result is the explicit variation to match data. No other circular steps (self-definitional equations or uniqueness theorems) are exhibited in the provided text.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

The claim rests on the validity of the off-shell fragmentation model and on the choice of jet mass and multiplicity values whose effects are studied; these are not derived from first principles within the abstract.

free parameters (2)

jet mass
The paper explicitly studies the effect of varying jet mass on the v2 curve, indicating it functions as a tunable parameter.
hadron multiplicity
Hadron multiplicity per jet is varied to examine its influence on the shape of v2, indicating it is treated as a free parameter.

axioms (1)

domain assumption The off-shell fragmentation model accurately describes hadron production in jets with non-negligible virtualities.
The abstract states that this recently developed model is used because virtualities are not negligible.

pith-pipeline@v0.9.0 · 5631 in / 1275 out tokens · 33160 ms · 2026-05-24T22:01:06.648753+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

19 extracted references · 19 canonical work pages · 7 internal anchors

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Qi Wang, Pei-Pin Y ang, Fu-Hu Liu, Results in Physics 12, 259-267 (2019); arXiv:1811.09883 4 Correlations in Massive Jets Karoly Urmossy Figure 1: v2 as a function of pT obtained from long-range ( |∆y| ≥ 2) ∆y − ∆ϕ correlations. Theoretical curves are obtained using an off-shell fragmentation model for a two-jet hadronic ﬁnal state with back-to- back jets...

work page internal anchor Pith review Pith/arXiv arXiv 2019

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work page internal anchor Pith review Pith/arXiv arXiv 2017

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work page internal anchor Pith review Pith/arXiv arXiv 2013

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Urmossy etal., Eur

K. Urmossy etal., Eur . Phys. J. A53 (2017) no.2, 36; PoS DIS2017 (2018) 183; Acta Phys.Polon. B 48 (2017) 1225; PoS DIS2016 (2016) 054

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M. Ishihara, arXiv:1904.03363

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E-Q. Wang, Y -Q. Ma, L-N. Gao, S-H. Fan, arXiv:1906.03616

work page arXiv 1906

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A.N. Tawﬁk, H. Y assin, E.R.A. Elyazeed, arXiv:1905.127 56

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S. Tripathy, A. Bisht, R. Sahoo, A. Khuntia, P .S. Malavi ka, arXiv:1905.07418

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K. Shen, G.G. Barnafoldi, T.S. Biro, arXiv:1905.05736

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P . Chakraborty, T. Tripathy, S. Pal, S. Dash, arXiv:190 4.12938

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work page internal anchor Pith review Pith/arXiv arXiv 2019

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Transverse momentum $p_{\mathrm{T}}$ spectra of strange particles production in different collisions at $\sqrt{s_{NN}}= 2.76, 5.02,$ and $7$ TeV

Hayam Y assin, Eman R. Abo Elyazeed, A. Phys. Pol. B 50, 37 (2019); arXiv:1812.04746

work page internal anchor Pith review Pith/arXiv arXiv 2019

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Comparing a few distributions of transverse momenta in high energy collisions

Qi Wang, Pei-Pin Y ang, Fu-Hu Liu, Results in Physics 12, 259-267 (2019); arXiv:1811.09883 4 Correlations in Massive Jets Karoly Urmossy Figure 1: v2 as a function of pT obtained from long-range ( |∆y| ≥ 2) ∆y − ∆ϕ correlations. Theoretical curves are obtained using an off-shell fragmentation model for a two-jet hadronic ﬁnal state with back-to- back jets...

work page internal anchor Pith review Pith/arXiv arXiv 2019