REVIEW
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.
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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
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
- 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.
The abstract, sentence by sentence
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
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| 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 was examined, and what was not
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Figures
Figures reproduced from arXiv:hep-ph/9902341 by the authors.
References
How later papers used it
162 later papers cite it
2 later papers by other authors are listed below: 2 used its method or tool.
Uses its method or tool 2 of 14 papers with this label
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Used an analytic model based on a correlation or shape function depending on very few nonperturbative parameters to include hadronization effects in its thrust distribution.
Thrust distribution in electron-positron annihilation at full NNNLL+NNLO (and beyond) in QCD (2025) · 0.96 · paraphrased: the licence does not allow quoting
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For simplicity, we use a phenomenological form for the leading non-perturbative power correction as suggested in [ref] , and fit the unknown parameters from a Monte Carlo program.
NNLL Resummation for Projected Three-Point Energy Correlator (2023) · Hadronization corrections · 0.93
How the literature uses it
165 arXiv papers cite this in 233 sentences
Papers whose main result relates to this one's
States the same result 1 paper
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We argue that for $e \sim \Lambda_{QCD}/Q$ all power corrections of the form $1/\lr{Qe}^n$ have to be taken into account for an arbitrary $n$.
Power corrections to the event shape in $e^+e^-$ annihilation · 0.80
Papers citing it · 147 sentences without a confident label
Builds on it 1 paper
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This approach extends earlier studies [ref] , which included only the leading power correction and showed improved agreement with data for moderately small angles.
Collinear limit of the energy-energy correlator in $e^+ e^-$ collisions: transition from perturbative to non-perturbative regimes · Introduction · 0.94
Uses its method or tool 13 papers
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In SCET, this is implemented by convolving $S_PT$ with a universal shape function $F(k)$ describing soft radiation at $k∼Λ_QCD$ [ref] , [equation] with $F(k)$ normalized as $∫dk F(k) = 1$ and independent of $μ_S$.
Centauric 1-Jettiness in DIS and Universal Power Corrections · Non-perturbative Power Corrections · 0.84
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Using repl in the leading-order factorization theorem for the cross-section where an inclusive measurement of thrust is performed for $τ≪1$ [ref] , we obtain:
Parton Fragmentation within an Identified Jet at NNLL · Introduction · 0.82
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Our numerical results include resummation up to NNLL$'$ resummation and include nonperturbative hadronization corrections through a shape function [ref] .
A case study of quark-gluon discrimination at NNLL' in comparison to parton showers · Introduction · 0.90
Compares with it 2 papers
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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
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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
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The assumption of linearity in $Λ_QCD$ is supported by predictions from hadronization [ref] , Wilson loop [ref] and renormalon [ref] models.
Scaling violation in power corrections to energy correlators from the light-ray OPE · Introduction · 0.98
Cites it as background 59 papers
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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
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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
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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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