Recognition: unknown
Les Houches study on inclusive jet production at NNLO+NNLL
Pith reviewed 2026-05-07 16:17 UTC · model grok-4.3
The pith
Scale variations underestimate higher-order effects in inclusive jet production for common jet radii.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
NNLO QCD calculations supplemented by NNLL small-jet-radius resummation show that resummation appreciably modifies the scale uncertainty and, for some scale choices, shifts the central inclusive jet cross section. The study concludes that scale variations in fixed-order and resummed calculations can drastically underestimate the impact of higher orders for commonly used jet radius parameters, rendering missing higher-order estimates obtained via scale variations unreliable.
What carries the argument
NNLO fixed-order QCD calculations combined with next-to-next-to-leading-logarithmic resummation of small-jet-radius logarithms.
If this is right
- Resummation must be included when assessing perturbative uncertainties for inclusive jet observables at typical LHC jet radii.
- Precision extractions of parton distribution functions or the strong coupling from jet data require uncertainty methods that go beyond scale variation.
- Scale-variation bands reported in current NNLO jet analyses should be treated as underestimates of the true theoretical error.
- Further all-order or higher-logarithm resummation may be needed to stabilize predictions for small-radius jets.
Where Pith is reading between the lines
- The same underestimation may affect other jet and jet-substructure observables that rely on small cone sizes.
- Experimental collaborations could test the conclusion by comparing data to both NNLO and NNLO+NNLL predictions and checking whether the larger theory bands better describe the measurements.
- Alternative uncertainty techniques, such as explicit variation of the resummation scale or matching to parton showers, become more important when scale variation alone is shown to be insufficient.
Load-bearing premise
The NNLO plus NNLL calculation captures the dominant higher-order perturbative effects for the chosen jet radii and scale choices.
What would settle it
A complete N3LO calculation for inclusive jet production whose central value lies inside the NNLO scale-variation band while differing substantially from the NNLO+NNLL central value would falsify the claim that scale variations underestimate the higher-order shift.
read the original abstract
Jet production at the LHC is a powerful probe of QCD, making it ideal for precision tests and determinations of QCD parameters such as parton distribution functions and the strong coupling constant. To make the most of the abundant jet production data collected at the LHC, precise calculations are required. While state-of-the-art calculations reach next-to-next-to-leading order (NNLO) QCD accuracy, a critical assessment of the remaining uncertainties arising from non-perturbative effects and missing higher orders remains crucial for correctly interpreting comparisons between theory and data. Scale variation is nearly always used to determine effects from missing higher orders. In this article, we reassess this method in the context of inclusive jet production by performing NNLO QCD calculations supplemented by small-jet-radius resummation through next-to-next-to-leading-logarithmic accuracy (NNLL). We find that NNLL resummation can have an appreciable impact on the scale uncertainty for inclusive jet cross sections, and, for some scale choices, can lead to sizeable shifts of the central cross section. We conclude that scale variations in fixed-order and resummed calculations can drastically underestimate the impact of higher orders for commonly used jet radius parameters, and that missing higher-order estimates obtained via scale variations should be considered unreliable. Our findings add further evidence to the importance of going beyond scale variations in jet and jet substructure calculations.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports results from a Les Houches workshop study on inclusive jet production at the LHC. It performs explicit NNLO QCD calculations for jet cross sections supplemented by small-jet-radius resummation at NNLL accuracy. Numerical comparisons between fixed-order NNLO and NNLO+NNLL predictions show that resummation can produce appreciable shifts in central values (for certain scale choices) and substantial changes to scale-variation uncertainties. The authors conclude that conventional scale variations in both fixed-order and resummed calculations underestimate the size of missing higher-order corrections for commonly used jet radii, rendering such estimates unreliable.
Significance. If the numerical results and their interpretation hold, the work provides concrete evidence that scale variation is insufficient for reliable uncertainty quantification in jet phenomenology. This would strengthen the case for incorporating resummation or alternative methods (e.g., Bayesian or machine-learning-based uncertainty estimates) in precision LHC analyses, with direct relevance to PDF fits and strong-coupling determinations. The collaborative Les Houches format and explicit NNLO+NNLL implementation are positive features that enhance the credibility of the presented comparisons.
major comments (2)
- The central claim that scale variations 'drastically underestimate' higher orders for commonly used jet radii (R = 0.4–0.7) rests on the small-R resummation accurately capturing the dominant missing contributions at these values. The manuscript must demonstrate this quantitatively by showing the size of the NNLL corrections as a function of R (including at R = 0.4) and by assessing the validity of the small-R approximation (e.g., via the magnitude of ln(1/R) or comparison to non-small-R terms). Without such evidence, the extrapolation from the parametric small-R limit to experimental radii remains a load-bearing assumption that is not yet fully substantiated.
- The abstract and results sections note that sizeable shifts occur 'for some scale choices.' The paper should specify which scale choices are representative of current LHC analyses and demonstrate that the underestimation conclusion is robust (or not) for those standard choices, rather than depending on particular ad-hoc selections.
minor comments (2)
- The abstract could more explicitly state the range of jet radii and kinematic cuts used in the numerical study to allow readers to immediately assess relevance to typical ATLAS/CMS measurements.
- A brief discussion of non-perturbative corrections (hadronization, underlying event) and their interplay with the resummed perturbative results would help contextualize the quoted uncertainties.
Simulated Author's Rebuttal
We thank the referee for their thorough review and positive evaluation of the significance of our work. We address each of the major comments below and have made revisions to the manuscript to incorporate the suggested improvements.
read point-by-point responses
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Referee: The central claim that scale variations 'drastically underestimate' higher orders for commonly used jet radii (R = 0.4–0.7) rests on the small-R resummation accurately capturing the dominant missing contributions at these values. The manuscript must demonstrate this quantitatively by showing the size of the NNLL corrections as a function of R (including at R = 0.4) and by assessing the validity of the small-R approximation (e.g., via the magnitude of ln(1/R) or comparison to non-small-R terms). Without such evidence, the extrapolation from the parametric small-R limit to experimental radii remains a load-bearing assumption that is not yet fully substantiated.
Authors: We agree that additional quantitative support for the applicability of the small-R resummation at experimental jet radii would strengthen the manuscript. In the revised version, we include a new panel or figure displaying the NNLL correction relative to NNLO as a function of R for fixed pT, explicitly including R=0.4. We also add text assessing the size of ln(1/R), which ranges from approximately 0.36 for R=0.7 to 0.92 for R=0.4, and discuss that although the small-R approximation is used, the resummation captures the leading logarithmic enhancements, and the effects persist in the matched calculation. This addresses the concern about the load-bearing assumption. revision: yes
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Referee: The abstract and results sections note that sizeable shifts occur 'for some scale choices.' The paper should specify which scale choices are representative of current LHC analyses and demonstrate that the underestimation conclusion is robust (or not) for those standard choices, rather than depending on particular ad-hoc selections.
Authors: We appreciate this clarification request. We have updated the abstract and the relevant results sections to explicitly identify the scale choices used, noting that the central scale is chosen as μ = p_T (the jet transverse momentum) with variations by a factor of two, which is standard in many LHC jet analyses. We demonstrate that for these representative choices, the scale variation bands in the NNLO calculation are smaller than the shifts induced by including NNLL resummation in several kinematic regions, supporting the conclusion that scale variations underestimate the higher-order effects. This makes the finding more directly applicable to current practices. revision: yes
Circularity Check
No significant circularity; central claim from explicit numerical comparison
full rationale
The paper derives its conclusion that scale variations underestimate higher-order effects by performing explicit NNLO fixed-order calculations supplemented with NNLL small-R resummation and directly comparing the resulting cross sections and uncertainty bands for inclusive jet production. This chain relies on standard perturbative QCD computations and observed numerical shifts rather than any self-definitional equivalence, fitted parameters presented as predictions, or load-bearing self-citations that reduce the argument to unverified prior claims by the same authors. The resummation provides an independent assessment of missing higher orders outside the fixed-order framework, and the paper remains self-contained against external benchmarks without reducing its key result to its inputs by construction.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Perturbative expansion of QCD is valid and convergent at NNLO+NNLL for inclusive jet production at LHC energies
- domain assumption NNLL resummation accurately approximates the dominant logarithmic higher-order corrections for small jet radii
Reference graph
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discussion (0)
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