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From oxygen to lead: testing a common QGP description with high-$p_\perp$ probes

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Bithika Karmakar, Dusan Zigic, Magdalena Djordjevic

High Energy Physics - Phenomenology · Submitted 9 Nov 2026 · 73 references

Pith's verdict: A clear, well-structured predictions paper that systematically tests the common QGP description across four collision systems, though the universal hydro start-time assumption needs more scrutiny.

T0 · AI review

How this review was made: An AI referee (deepseek/deepseek-v4-flash) read the paper on November 10, 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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arXiv ID2611.12404 (version 1)
Pith IDS5CK5DUP, Pith's permanent record of this paper and its review
CitationBithika Karmakar, Dusan Zigic, Magdalena Djordjevic. "From oxygen to lead: testing a common QGP description with high-$p_\perp$ probes." arXiv:2611.12404 (2026). https://pith.science/paper/S5CK5DUP
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The paper

The paper claims

A single set of energy-loss parameters, coupled to system-specific hydrodynamics, simultaneously reproduces high-$p_\perp$ suppression and elliptic flow from O+O to Pb+Pb, demonstrating a common QGP description.

The reading

Does the same quark-gluon plasma description work from light ions like O+O to heavy systems like Pb+Pb? This paper answers yes, using a fixed set of microscopic energy-loss parameters within the DREENA framework together with system-dependent hydrodynamic evolution calibrated to soft observable. The calculation reproduces the observed ordering of suppression ($R_{\mathrm{AA}}$) and predicts finite elliptic and triangular flow ($v_2$, $v_3$) with comparable magnitudes across the four systems. Key predictions—such as the near momentum-independence of $v_2/(1-R_{\mathrm{AA}})$ in light ions and the differential cumulant ratios—provide experimental tests of how far the unified description extends.

What carries the argument

The central machinery is the DREENA-A framework coupled to event-by-event viscous hydrodynamic evolution (T$_R$ENTo initial conditions + VISHNew). DREENA-A computes radiative and collisional energy loss in a finite, dynamical QCD medium using the same parameter set for all systems. The bulk evolution is calibrated separately for each system using soft-sector observables (multiplicity and $v_2\{4\}$) and then held fixed for the high-$p_\perp$ predictions. This combination allows a common microscopic description of energy loss while accounting for system-specific medium properties.

Extended reading notes

Core claim

The paper's central claim is that a unified description of high-$p_\perp$ probes in heavy-ion collisions, based on the DREENA approach with event-by-event hydrodynamic evolution, works across a wide range of collision systems—from O+O and Ne+Ne to Xe+Xe and Pb+Pb—without adjusting the microscopic energy-loss parameters. By fixing the same radiative and collisional energy-loss prescription and calibrating only the system-specific bulk evolution (initial conditions, shear viscosity) to soft hadron data, the calculation quantitatively captures the observed ordering of $R_{\mathrm{AA}}$ and produces finite $v_2$ and $v_3$ values that agree with existing light-ion measurements and predict distinct centrality and mass dependences. The results suggest that the same QGP response governs both the average suppression and its directional dependence in small and large systems, with testable signatures such as the weak centrality dependence of $v_2$ in light ions, the stronger decline of $v_3$ toward peripheral collisions, and the near-constancy of $v_2/(1-R_{\mathrm{AA}})$ with momentum.

Load-bearing premise

The analysis assumes the same hydro starting time (τ0=1 fm) without a pre-equilibrium free-streaming stage for all four systems, based on a constraint from Pb+Pb (ref [58]), but the uncertainty of this assumption for light ions is not quantified.

Editorial extensions

If this is right

  • If correct, the predictions for $v_3$ in Ne+Ne and O+O provide a sensitive test of fluctuation-generated geometry in small systems, with a predicted stronger decline toward peripheral collisions compared to larger systems.
  • The near momentum-independence of $v_2/(1-R_{\mathrm{AA}})$ in light ions implies that the momentum dependence of suppression and elliptic flow are driven by the same factor, simplifying the interpretation of high-$p_\perp$ anisotropy.
  • The differential cumulant ratio $v_2\{4\}/v_2\{2\}$ at high $p_\perp$ offers a direct test of whether soft-sector fluctuation patterns persist in hard–soft correlations, with similar magnitudes and centrality trends as the low-$p_\perp$ ratio.
  • The flavor dependence (D vs B mesons) within the same framework provides a test of mass effects in energy loss, with predicted differences in $v_3/v_2$ ratios between large and small systems that can be confronted with future data.

Reading between the lines

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

  • The assumption of a common hydro starting time $\tau_0=1$ fm, validated in Pb+Pb but untested in light ions, is the weakest link; if future data deviate from predictions, it may point to a different pre-equilibrium stage in small systems.
  • The success of this unified description would suggest that the QGP formed in O+O collisions is sufficiently hot and extended for the same energy-loss formalism to apply, potentially narrowing the search for the minimum system size that exhibits QGP signatures.
  • The predictions for $v_2\{4\}/v_2\{2\}$ connecting soft and hard sectors suggest a new observable to probe event-by-event fluctuations of the medium structure, with implications for initial-state modeling beyond mean geometry.
Original abstract

The observation of suppression and finite high-$p_\perp$ elliptic anisotropy in O+O and Ne+Ne raises the question of whether a common quark--gluon plasma (QGP) description can simultaneously account for both observables across systems from oxygen to lead. We present predictions using event-by-event bulk evolution constrained by soft-sector observables and coupled to DREENA radiative and collisional energy loss, with the same microscopic parameter set for O+O, Ne+Ne, Xe+Xe, and Pb+Pb. The calculation reproduces the observed ordering of suppression and predicts elliptic anisotropies of comparable magnitude across the four systems in 10--20$\%$ collisions. We predict a modest centrality dependence of $v_2^{\mathrm{SP}}$ and a more pronounced decrease of $v_3^{\mathrm{SP}}$ toward peripheral light-ion collisions, in contrast to the corresponding trends in larger systems. In light ions, we predict that $v_2^{\mathrm{SP}}/(1-R_{AA})$ is nearly independent of momentum at high $p_\perp$. We further predict that the differential ratio $v_2\{4\}/v_2\{2\}$ depends only weakly on momentum at high $p_\perp$, with magnitudes and centrality trends broadly comparable to those of the measured soft-sector ratios, suggesting that the soft-sector fluctuation pattern persists in hard--soft correlations. Predictions for D and B mesons extend the comparison to probes of different flavors. Taken together, these system-size, harmonic, fluctuation, and flavor dependences provide experimental tests of how far a common QGP description extends.

Figures
Figure 2. shows that the calculation produces a finite high-p⊥ v SP 2 that falls with momentum in both O+O and Ne+Ne and has a magnitude comparable to the data. In Ref. [23], decorrelation between the hard and soft event planes leads to a nearly vanishing high-p⊥ v2. The present O+O v SP 3 measurements provide a further test, while Ne+Ne v SP 3 remains a prediction. Centrality provides a clearer distinction between the two harmonics (Fig. 3a,b). We predict that v SP 2 changes only moderately toward peripheral O+O and Ne+Ne collisions, whereas v SP 3 shows a more pro￾nounced decrease. Near 11…
Figure 3. FIG. 3. Centrality dependence of
Figure 4. FIG. 4. Predicted
Figure 5. FIG. 5. Predicted
Figure 6. FIG. 6. Centrality dependence of

Showing 5 of the paper's 6 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:2611.12404 by the authors.

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