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Large Jets at Hadron Colliders at Order $\alpha_s^3$: A Look Inside

High Energy Physics - Phenomenology · Submitted 26 Aug 1992 · 10 references

Pith's verdict: The first order-αs³ look inside the jet, and the paper is candid that its shape agreement comes from a tuned merging cutoff rather than a prediction.

T0 · AI review

How this review was made: An AI referee (selfhosted/deepseek-v4.1-flash) read the paper on November 13, 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 IDhep-ph/9208249 (version 1)
Pith ID7Z5H7SQV, Pith's permanent record of this paper and its review
CitationDavison E. Soper, Stephen D. Ellis, Zoltan Kunszt. "Large Jets at Hadron Colliders at Order $\alpha_s^3$: A Look Inside." arXiv:hep-ph/9208249 (1992). https://pith.science/paper/7Z5H7SQV
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Referee report
The paper

The paper claims

A third-order QCD calculation claims to describe not just how often jets are produced at a hadron collider, but how their energy is distributed inside the jet cone, and it agrees with CDF measurements at 100 GeV once a hand-set merging rule

The reading

The paper asks whether fixed-order perturbative QCD can say something about the inside of a jet, not merely about how many jets are made. At order $alpha_s^2$ a jet is a single parton and has no internal structure at all; at order $alpha_s^3$ a jet can contain two partons, so the calculated cross section begins to depend on the cone radius $R$ and on how energy is spread within the cone. The authors compute the inclusive single-jet cross section in $pp$ collisions at $sqrt{s}=1800$ GeV and $E_T=100$ GeV, together with a fractional transverse-energy profile $F(r,R,E_T)$ that records what share of a jet's energy lies inside an inner cone of radius $r

What carries the argument

The load-bearing object is the fractional transverse-energy profile $F(r,R,E_T)$: for a sample of jets of transverse energy $E_T$ defined by a cone of radius $R$, it is the average fraction of the jet's energy falling inside a concentric inner cone of radius $r<R$. The authors compute the complement $1-F$ rather than $F$ itself, because the energy in the annulus between $r$ and $R$ is free of the collinear singularity at $r=0$; the numerator is a purely order $alpha_s^3$ integral of the three-parton cross section over the annulus, normalized to $E_T$ times the Born cross section. The second piece of machinery is the merging rule. The default algorithm merges any two partons that can be covered by one cone, up to a separation of $2R$, which counts two partons sitting $2R$ apart with a valley between them as a single jet centered on the valley. The authors add a cutoff $R_{sep} leq 2R$ so that partons separated by more than $R_{sep}$ are not merged, and they set $R_{sep}=1.3R$ as a simple stand-in for what an experimental jet algorithm would do.

Extended reading notes

Core claim

The central claim is that an order $alpha_s^3$ perturbative calculation of single-jet production, equipped with a jet definition that includes a merging cutoff, reproduces the CDF measurements of both the jet rate versus cone radius and the distribution of transverse energy inside the jet, at $sqrt{s}=1800$ GeV and $E_T=100$ GeV. The authors show that the order $alpha_s^3$ cross section is far less sensitive to the renormalization/factorization scale $mu$ than the Born result, with residual scale dependence estimated at about 10%, and that its dependence on the cone radius $R$ is qualitatively right: stable near $R approx 0.7$, dominated by real emission at large $R$, and dominated by the virtual correction at small $R$. Fitting both data and theory to $sigma = A + B ln R + C R^2$, they find the $R$-independent piece $A$ agrees well, the piece $C$ associated with radiation far from the jet axis agrees at $mu = E_T/2$, but the piece $B$ associated with radiation near the jet direction comes out too small. Lowering the scale to $E_T/4$ raises $B$ toward the data while overshooting $C$; adding the merging cutoff $R_{sep}=1.3R$ at $mu = E_T/4$ then restores $C$ and leaves both parameters in reasonable agreement with the measured values.

Load-bearing premise

The agreement on jet shapes depends on a merging cutoff $R_{sep}=1.3R$ that is chosen by hand to imitate the experimental jet algorithm, with its detailed justification deferred to a paper still in preparation.

Editorial extensions

If this is right

  • Fixed-order QCD at order $alpha_s^3$ becomes a usable tool for jet physics at hadron colliders, since the residual scale dependence drops to roughly 10% and the predicted radius dependence of the cross section has the right shape.
  • The cone radius $R approx 0.7$ is singled out as the size at which the order $alpha_s^3$ result is most stable, which is the size actually used in the CDF inclusive jet analysis.
  • The comparison of the fitted parameters $B$ and $C$ against data gives a diagnostic for how much radiation is emitted near the jet axis versus far from it, and hence a handle on the effective strong coupling.
  • Because the merging rule changes the predicted energy profile at the cone edge by a sizeable amount while changing the total cross section by at most about 10%, details of jet definition matter more for jet substructure than for jet rates.
  • Differences in internal jet structure are suggested as a possible way to separate quark-initiated from gluon-initiated jets.

Reading between the lines

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

  • If the merging cutoff is really standing in for finite angular resolution and fragmentation spread, then its value should scale with $E_T$ and with the detector's angular resolution rather than stay fixed at $1.3R$; a measurement of the profile at several $E_T$ would test that.
  • The pattern of a correct $A$, a too-small $B$ and a correct $C$ at $mu = E_T/2$ reads like a mismatch in the angular distribution of radiation rather than an overall normalization error, which points at higher-order corrections that populate the collinear region rather than at the parton distributions.
  • Since the profile is computed at lowest nontrivial order, its scale dependence is monotonic, so the fact that data prefer a lower scale than the cross section does is itself a signal that the two observables need different effective scales at this order.
  • A natural extension is to use the same profile machinery on photon-tagged or $Z$-tagged jet samples, where the parton flavour of the jet is fixed at leading order, to see whether the merging prescription is flavour-independent.
Original abstract

Results from the study of hadronic jets in hadron-hadron collisions at order $\alpha_s^3$ in perturbation theory are presented. The focus is on various features of the internal structure of jets. The numerical results of the calculation are compared with data where possible and exhibit reasonable agreement.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 2,847 input tokens, $0.0001 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.38 · human participants 0.01 · controlled comparison 0.06 · randomized assignment 0.01 · states quantitative result 0.09 · compares with prior results 0.49 · mentions code or data availability 0.03.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

Results from the study of hadronic jets in hadron-hadron collisions at order $\alpha_s^3$ in perturbation theory are presented. The focus is on various features of the internal structure of jets. The numerical results of the calculation are compared with data where possible and exhibit reasonable agreement.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 Results from the study of hadronic jets in hadron-hadron collisions at order $\alpha_s^3$ in perturbation theory are presented. contribution 0.99 0.89 0.12 asserted 0.98
s1 The focus is on various features of the internal structure of jets. contribution 0.98 0.57 0.07 asserted 0.93
s2 The numerical results of the calculation are compared with data where possible and exhibit reasonable agreement. result 0.94 0.89 0.36 asserted 0.84

What kind of paper the classifier reports this is: theoretical result 0.68 · evidence from simulation or computation 0.96.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Inclusive jet cross section versus R for √ s = 1800 GeV, ET = 100 GeV and 0.1 < |η| < 0.7 with µ = ET /4, ET /2, ET compared to data from CDF[3]; the dot-dash curve is explained in the text. Also indicated for the three µ choices are the values of the R-independent Born cross section

Figures reproduced from arXiv:hep-ph/9208249 by the authors.

References
How the literature uses it

32 arXiv papers cite this in 37 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 22 sentences without a confident label

Builds on it 1 paper
Compares with it 1 paper
  • This is in contrast to, e.g., the integrated jet shape $Ψ(R)$ [ref] , which requires a detailed calculation even for its leading order behavior [ref] .

    Angular Scaling in Jets · Calculating the average · 0.98

Cites it as background 13 papers

Discussion

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