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arxiv: 1907.08794 · v1 · pith:3JVSFF5Pnew · submitted 2019-07-20 · ✦ hep-ph

ITMD factorization and broadening effects in production of forward di-jets

Krzysztof Kutak This is my paper

Pith reviewed 2026-05-24 18:57 UTC · model grok-4.3

classification ✦ hep-ph
keywords dijet correlationsgluon saturationSudakov resummationITMD factorizationforward productionproton-lead collisionsazimuthal broadening
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The pith

ITMD calculations require broadening from gluon saturation and Sudakov resummation to describe ATLAS forward di-jet data.

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

The paper compares ITMD factorization predictions for azimuthal angle correlations in forward-forward di-jets against ATLAS measurements in both proton-proton and proton-lead collisions. Standard ITMD results without additional broadening fail to reproduce the observed decorrelation patterns in the data. Including the combined broadening from gluon saturation at small x and Sudakov resummation brings the calculations into agreement with experiment. A sympathetic reader would conclude that both mechanisms must be treated together to capture the physics of forward di-jet production.

Core claim

The comparison shows that the broadening effect due to interplay of both the gluon saturation and the Sudakov resummation is necessary to describe the data.

What carries the argument

ITMD factorization framework applied to forward di-jet azimuthal correlations, incorporating gluon saturation in TMD distributions together with Sudakov resummation for broadening.

If this is right

  • Models omitting either gluon saturation or Sudakov resummation will underpredict the azimuthal broadening seen in forward di-jets.
  • The same interplay should affect other small-x observables measured in proton-nucleus collisions.
  • Nuclear enhancement of broadening in p-Pb data provides a direct test of saturation contributions.
  • The framework allows extraction of small-x gluon distributions once the broadening is properly accounted for.

Where Pith is reading between the lines

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

  • The result suggests that similar combined treatments will be needed for other processes like forward hadron or photon production at the LHC.
  • It implies that pure saturation models without resummation, or pure perturbative calculations without saturation, are incomplete for forward kinematics.
  • Future higher-precision measurements at the LHC or EIC could isolate the relative size of each broadening source.

Load-bearing premise

That mismatches between ITMD results and data arise specifically from missing saturation-Sudakov broadening rather than other unmodeled effects or experimental uncertainties.

What would settle it

New data or refined analysis showing that ITMD predictions with saturation and Sudakov broadening still deviate significantly from the measured azimuthal distributions beyond uncertainties.

Figures

Figures reproduced from arXiv: 1907.08794 by Krzysztof Kutak.

Figure 1
Figure 1. Figure 1: Broadening of azimuthal decorrelations in p-Pb collisions vs p-p collisions for different sets of cuts imposed on the jets’ transverse momenta. The plots show normalized cross sections as functions of the azimuthal distance between the two leading jets, ∆φ. The points show the experimental data [3] for p-p and p-Pb, where the p-Pb data were shifted by a pedestal, so that the values in the bin ∆φ ∼ π are th… view at source ↗
read the original abstract

I report on the recent result of comparison of forward-forward dijet correlations in azimuthal angle as measured by the ATLAS collaboration in the proton-proton and proton-lead collisions to calculations within ITMD factorization framework [1]. The comparison shows that the broadening effect due to interplay of both the gluon saturation and the Sudakov resummation is necessary to describe the data.

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 compares forward-forward dijet azimuthal correlations measured by ATLAS in pp and pPb collisions to calculations performed in the ITMD factorization framework. It concludes that the broadening effect due to the interplay of gluon saturation and Sudakov resummation is necessary to describe the data.

Significance. If the central claim is robust, the result would provide evidence that both saturation and Sudakov effects must be included simultaneously to model forward dijet decorrelation at the LHC, offering a potential constraint on small-x gluon distributions in a kinematic regime where both effects are relevant.

major comments (2)
  1. [Results and comparison section (exact section number not specified in provided text)] The necessity claim for broadening rests on the assumption that mismatches between data and the ITMD baseline (without saturation+Sudakov broadening) are specifically due to the omitted broadening rather than other unmodeled effects. The manuscript should include explicit side-by-side comparisons (with/without broadening) together with quantitative measures such as χ² per degree of freedom or residual plots to demonstrate that alternative adjustments (e.g., different UGD parametrizations or scale choices) cannot restore agreement.
  2. [Theoretical framework and numerical setup] The ITMD framework implementation requires specification of the unintegrated gluon distributions, kinematic cuts, and factorization/renormalization scale choices used for the baseline calculations. Without variation of these inputs or an assessment of their impact on the azimuthal decorrelation, it remains unclear whether the observed discrepancy is uniquely attributable to missing broadening.
minor comments (1)
  1. [Abstract] The abstract states the conclusion but does not indicate the specific observables (e.g., Δφ distributions or moments) or collision systems used in the comparison; this should be clarified for readers.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments on our manuscript comparing ATLAS forward dijet data to ITMD factorization. The points raised concern the robustness of attributing discrepancies to broadening effects and the need for more explicit documentation of the numerical setup. We address each major comment below and indicate where revisions will be made.

read point-by-point responses

  1. Referee: The necessity claim for broadening rests on the assumption that mismatches between data and the ITMD baseline (without saturation+Sudakov broadening) are specifically due to the omitted broadening rather than other unmodeled effects. The manuscript should include explicit side-by-side comparisons (with/without broadening) together with quantitative measures such as χ² per degree of freedom or residual plots to demonstrate that alternative adjustments (e.g., different UGD parametrizations or scale choices) cannot restore agreement.

    Authors: We agree that strengthening the uniqueness of the broadening interpretation requires more explicit comparisons. The original manuscript presents the ITMD baseline without broadening and the version including saturation plus Sudakov effects, but does not include χ² values or residual plots. In the revised version we will add side-by-side azimuthal correlation plots (with and without broadening) for both pp and pPb data sets, together with χ² per degree of freedom for each case. A comprehensive scan over all alternative UGD parametrizations lies outside the scope of the present study; however, we will discuss the sensitivity to the two main UGD choices employed and note that scale variations alone do not restore agreement with the data in the region where broadening is relevant. revision: partial

  2. Referee: The ITMD framework implementation requires specification of the unintegrated gluon distributions, kinematic cuts, and factorization/renormalization scale choices used for the baseline calculations. Without variation of these inputs or an assessment of their impact on the azimuthal decorrelation, it remains unclear whether the observed discrepancy is uniquely attributable to missing broadening.

    Authors: The manuscript references the specific ITMD implementation and the UGD parametrizations used, but we acknowledge that a consolidated description of the numerical setup is missing. In the revision we will add a dedicated paragraph (or subsection) that explicitly lists: (i) the UGD parametrizations and their parameters, (ii) the kinematic cuts applied to match the ATLAS forward dijet selection, and (iii) the default factorization and renormalization scale choices. We will also include a short assessment of scale variation (varying μ by a factor of two) and its effect on the azimuthal decorrelation, showing that such variations do not eliminate the need for the broadening term. revision: yes

Circularity Check

0 steps flagged

No significant circularity in phenomenological data comparison

full rationale

The paper performs a comparison of existing ITMD factorization calculations (referenced to prior work) against external ATLAS data on di-jet azimuthal correlations. The claim that broadening from saturation and Sudakov effects is necessary follows directly from the degree of agreement or mismatch with that independent dataset. No derivation, ansatz, or prediction is constructed within the paper that reduces by definition or self-citation to its own inputs; the result is externally falsifiable against measured data rather than self-referential.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no information on free parameters, axioms, or invented entities; ledger is therefore empty.

pith-pipeline@v0.9.0 · 5566 in / 944 out tokens · 17517 ms · 2026-05-24T18:57:09.290484+00:00 · methodology

discussion (0)

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Reference graph

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