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Power corrections to event shapes and factorization

High Energy Physics - Phenomenology · Submitted 15 Feb 1999 · 23 references

Pith's verdict: The shape-function convolution framework is the real contribution and it holds up, but the moment relations in Eqs. 26–28 and 37 carry a sign error a referee should catch.

T0 · AI review

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arXiv IDhep-ph/9902341 (version 1)
Pith IDNSH5OY77, Pith's permanent record of this paper and its review
CitationG.P.Korchemsky, G.Sterman. "Power corrections to event shapes and factorization." arXiv:hep-ph/9902341 (1999). https://pith.science/paper/NSH5OY77
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Referee report
The paper

The paper claims

The paper argues that near the two-jet limit the thrust and heavy-jet-mass distributions factor into a convolution of one energy-independent soft shape function with a resummed perturbative spectrum, so that every power correction of the形式$

The reading

Near the two-jet limit of electron-positron annihilation, the thrust and heavy-jet-mass distributions are dominated by soft radiation carrying a small fraction of the beam energy. The paper argues that this soft radiation separates from the evolution of the narrow jets and can be packaged into a shape function: a probability distribution for how much light-cone energy the soft quanta deposit in each hemisphere. If that holds, the measured distribution is a convolution of this nonperturbative function with a perturbatively resummed spectrum, and every power correction of the form $1/(eQ)^n$ is generated by the same function rather than by a separate parameter for each $n$. The payoff is predictive: the shape function is fixed once, at a single energy, and must then describe the same physics at every energy, while its moments are vacuum expectation values of energy-flow operators that also control the energy-energy correlation.

What carries the argument

The shape function itself. For thrust it is defined by the Laplace transform $��_0^�� d�� e^{-�ͧ�/Q} f_T(��;��) = ��(-S_{NP}(Q/��,��))$, which ties its moments to the ambiguous low-momentum integrals of the resummed exponent, and equivalently by the operator expression $f_T(��) = ��0|W^��(0) ��(�� - �� d�� n w_T(n) E(n)) W(0)|0��$, where $W$ is the product of eikonal Wilson lines of the two jets and $E(n)$ is an energy-flow operator measuring energy density in direction $n$, with weight $w_T(n) = 1-|��cos��|$. The weight vanishes along the jet directions, which is why the shape function has no collinear singularities. Taking moments of $f_T$ turns the weights into integrals of Green functions $G(n_1��n_N) = ��0|W^�� E(n_1)��E(n_N) W|0��$; these are the universal objects, independent of which event shape was chosen, and the single-energy-flow correlator $G(��)$ is what the leading $1/Q$ energy-energy correlation measures.

Extended reading notes

Core claim

The central claim is that the differential thrust and heavy-jet-mass distributions in the two-jet limit, $e = 1-T$ or $e = M^2/Q^2$, can be written as convolutions of a nonperturbative infrared shape function with a resummed perturbative cross section. The shape function depends on a factorization scale $��$ that separates soft from hard dynamics, and differs from one event shape to another, but is independent of the center-of-mass energy $Q$. The authors derive this twice: once from the kinematics of soft emission, writing the hemisphere masses as perturbative pieces plus soft light-cone sums $M^2_{R,L}/Q^2 + ��_{R,L}/Q$ and factorizing the soft distribution $f(��_R,��_L)$; and once from the resummed exponent, where the nonperturbative part of the Sudakov exponent $S_{NP} = ��_{n>0} (��/Q)^n ��_n(��)/n!$ is the Laplace transform of the thrust shape function $f_T(��)$, so that the moments of $f_T$ are exactly the $��_n$. The familiar shift $d��_{PT}(t)/dt �� d��_{PT}(t-��_1/Q)/dt$ reappears as the special case in which $f_T$ is a delta function, and the same limit gives half that shift for the heavy-jet mass, a parameter-free relation between the two observables. Beyond the leading shift, the shape function organizes all powers $1/(tQ)^n$ and $1/(��Q)^n$, and its variance controls the smearing that the simple shift misses.

Load-bearing premise

Soft gluon emission from the two jets is incoherent and depends only on the jet directions and colour charges, so that the soft distribution factorizes from jet evolution and carries no dependence on the beam energy; the authors note this fails at the level of the $��f$ term from a gluon splitting into opposite hemispheres.

Editorial extensions

If this is right

  • A shape function fitted to thrust data at one energy predicts the thrust distribution at all higher energies with no new parameters.
  • All corrections of the form $1/(tQ)^n$ follow from the moments of one function, with the simple shift of the perturbative spectrum as the delta-function limit.
  • The nonperturbative shift of the mean heavy-jet mass is exactly half that of the mean thrust, a relation that holds for any shape function.
  • Moments of the shape function are universal energy-flow matrix elements, so event-shape measurements constrain the same quantities that appear in energy-energy correlations.
  • The variance of the thrust distribution receives no $1/Q$ correction; its leading nonperturbative piece is $1/Q^2$ and is tied to connected two-point energy-flow correlations.

Reading between the lines

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

  • If the shape function really carries no $Q$ dependence, a global fit across energies is over-determined, and the drift of fitted $��_1$ values with energy becomes a direct handle on the size of the neglected non-factorizing term $��f$ and of higher $1/Q$ corrections.
  • The Green functions are singular only where two directions coincide, and stereographic projection maps them onto a plane; that suggests the energy-flow correlators might be computable in a two-dimensional effective description, which the paper only gestures toward.
  • Because the construction needs only an additive weight on soft momenta that vanishes along the jets, the same convolution should exist for any infrared-safe observable of that class, making the shape-function idea as broad as the class of such weights.
  • The same structure should carry over to hadron-collider event shapes and jet masses, where soft radiation is emitted by more than two coloured legs; whether the shape function stays universal there is an open and testable question.
Original abstract

We study power corrections to the differential thrust, heavy mass and related event shape distributions in $e^+e^-$-annihilation, whose values, $e$, are proportional to jet masses in the two-jet limit, $e\to 0$. The factorization properties of these differential distributions imply that they may be written as convolutions of nonperturbative "shape" functions, describing the emission of soft quanta by the jets, and resummed perturbative cross sections. The infrared shape functions are different for different event shapes, and depend on a factorization scale, but are independent of the center-of-mass energy $Q$. They organize all power corrections of the form $1/(eQ)^n$, for arbitrary $n$, and carry information on a class of universal matrix elements of the energy-momentum tensor in QCD, directly related to the energy-energy correlations.

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, 3,789 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.14 · human participants 0.01 · controlled comparison 0.01 · randomized assignment 0.01 · states quantitative result 0.06 · compares with prior results 0.05 · mentions code or data availability 0.02.

The abstract, sentence by sentence

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

We study power corrections to the differential thrust, heavy mass and related event shape distributions in $e^+e^-$-annihilation, whose values, $e$, are proportional to jet masses in the two-jet limit, $e\to 0$. The factorization properties of these differential distributions imply that they may be written as convolutions of nonperturbative "shape" functions, describing the emission of soft quanta by the jets, and resummed perturbative cross sections. The infrared shape functions are different for different event shapes, and depend on a factorization scale, but are independent of the center-of-mass energy $Q$. They organize all power corrections of the form $1/(eQ)^n$, for arbitrary $n$, and carry information on a class of universal matrix elements of the energy-momentum tensor in QCD, directly related to the energy-energy correlations.

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 We study power corrections to the differential thrust, heavy mass and related event shape distributions in $e^+e^-$-annihilation, whose values, $e$, are proportional to jet masses in the two-jet limit, $e\to 0$. contribution 0.92 0.72 0.09 asserted 0.99
s1 The factorization properties of these differential distributions imply that they may be written as convolutions of nonperturbative "shape" functions, describing the emission of soft quanta by the jets, and resummed perturbative cross sections. interpretation 0.37 0.30 0.26 hedged possibility 0.98
s2 The infrared shape functions are different for different event shapes, and depend on a factorization scale, but are independent of the center-of-mass energy $Q$. result 0.86 0.46 0.15 asserted 1.00
s3 They organize all power corrections of the form $1/(eQ)^n$, for arbitrary $n$, and carry information on a class of universal matrix elements of the energy-momentum tensor in QCD, directly related to the energy-energy correlations. interpretation 0.67 0.60 0.41 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.99 · evidence from proof or derivation 0.75.

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. The comparison of the data with the QCD prediction for the

Figures reproduced from arXiv:hep-ph/9902341 by the authors.

References
How later papers used it

162 later papers cite it

Evidence: some. 156 of the citing papers share no author with it, and 18 of those carry a confident label from Pith's citation classifier.

Pith read 3 of the 225 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Uses its method or tool 2 of 14 papers with this label
How the literature uses it

165 arXiv papers cite this in 233 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 whose main result relates to this one's

Found among the papers closest to this one by title and main claim. Pith's classifier compared each pair's main results and a second model family confirmed the relation; checked against two further families, shown conflicts agreed 118 times in 120 and shown same results 218 times in 239. The quoted sentence is the other paper's main claim.

States the same result 1 paper

Papers citing it · 147 sentences without a confident label

Builds on it 1 paper
Uses its method or tool 13 papers
Compares with it 2 papers
  • The above definition provides an operator definition of $S_(ℓ_1^+,ℓ_2^+)$ in SCET, and is equivalent to the definition in Ref. [ref] .

    Factorization for generic jet production · Double Differential Hemisphere Mass Distribution · 0.99

  • For comparison, the hemisphere soft function with outgoing Wilson appearing in the double-differential hemisphere invariant-mass distribution in $e^+e^- →2$ jets [ref] is

    Factorization at the LHC: From PDFs to Initial State Jets · The $qq̅$ Soft Function · 0.98

Cites it as support 1 paper
Cites it as background 59 papers
  • In the last several years there has been a program [ref] to systematically reformulate the study of jet substructure in terms of correlation functions of energy flow operators [ref] , so-called energy correlators.

    Putting Jet Substructure on Track(s) · Introduction · 0.91

  • Asymptotic energy flow in collider experiments is characterized by correlation functions $⟨ℰ(n⃗_1) ℰ(n⃗_2) ⋯ℰ(n⃗_k) ⟩$ of the energy flow operator [ref] :

    Non-Gaussianities in Collider Energy Flux · Introduction · 0.89

  • This has been achieved by using factorization formulas [ref] , that separate perturbative dynamics at short distances from non-perturbative physics at long-distance scales encoded in universal functions such as parton distribution functions (PDFs) for the initial state or shape functions [ref] related to hadronization that can be extracted from reference processes and lattice data.

    Factorization for jet production in heavy-ion collisions · Introduction · 0.90

Discussion

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