REVIEW
Analytical and numerical methods for massive two-loop self-energy diagrams
High Energy Physics - Phenomenology · Submitted 22 Sep 1994 · 17 references
Pith's verdict: A solid, checkable methods paper: three usable representations for the massive two-loop self-energies, with one real presentational gap in the convergence conditions.
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Referee report
The paper
The paper claims
The paper gives three explicit ways to compute massive two-loop self-energy Feynman diagrams — hypergeometric series in the external momentum, complete elliptic integrals for the imaginary parts, and a one-dimensional integral with an integ
The reading
What carries the argument
Three pieces of machinery carry the argument. The dispersion relation converts a two-loop diagram into a one-dimensional integral over the discontinuity of a one-loop self-energy, $B_0$, contracted with a second one-loop function; partial fractioning in the subloop mass then reduces the two-loop object to a difference of simpler diagrams (Eq. 65). The Mellin–Barnes representation of a massive propagator, $1/(k^2-m^2)^α = (1/Γ(α))(1/2πi)∫ ds (-m^2)^s (k^2)^{-α-s} Γ(-s)Γ(α+s)$, relates the massive diagram to the known massless one with raised propagator powers, which is how the large-$p^2$ series and the partial differential equations (Eqs. 29–32) in the variables $x_i = m_i^2/p^2$ are generated. Finally, reduction of the cut integrals to Legendre normal form by partial fractions and partial integration turns the discontinuities into complete elliptic integrals, with the third-kind integral $Π(c,κ)$ continued to characteristic $c>1$ so that the two-particle and three-particle cuts cancel into a purely imaginary discontinuity.
Extended reading notes
Core claim
The central claim is that the massive two-loop self-energy diagrams $T_{123}$ and $T_{1234}$ are computable in closed or semi-closed form without any restriction to a special mass hierarchy. Concretely: (i) $T_{1234}$ is given in arbitrary $D$ as a small-$p^2$ multiple series (Eq. 17) plus a product of one-loop self-energies, and as a large-$p^2$ representation (Eq. 24) built from a vacuum-diagram factor times four-variable series $B_1$–$B_6$; (ii) the imaginary parts of $T_{123}$ and $T_{1234}$ in four dimensions reduce to complete elliptic integrals $K$, $E$ and $Π$ with explicit arguments in terms of the Källén variables, Eqs. 53 and 60, valid in all parameter regions; (iii) every two-loop diagram containing a self-energy subloop admits a one-dimensional representation with an elementary integrand, Eq. 68, specialised to Eqs. 70 and 73 for the two diagrams at hand. The authors also state plainly that the five-propagator master diagram is not covered: it is not of self-energy-insertion type, the massless case with arbitrary propagator powers is unavailable, and the Mellin–Barnes route is therefore blocked for it.
Load-bearing premise
The claim that the elliptic-integral formula for the three-particle cut holds in every parameter region depends on continuing the third-kind elliptic integral to characteristic $c>1$; the paper writes down only the imaginary jump of that continuation and defers the real part to a cited monograph, so the cancellation that makes the total discontinuity purely imaginary is asserted rather than demonstrated here.
Editorial extensions
If this is right
- Any electroweak two-loop self-energy with a self-energy insertion can be evaluated numerically from a single integral over elementary functions, replacing two-dimensional Monte Carlo integration with a fast deterministic quadrature.
- The imaginary parts of these diagrams can be computed from standard elliptic-integral algorithms in all parameter regions, so thresholds and particle-production cut contributions become cheap to evaluate.
- The arbitrary-$D$ hypergeometric results unify the many previously published massless and equal-mass special cases into one expression, since setting masses to zero or equal reduces the series to known ${}_3F_2$ and ${}_2F_1$ forms.
- The large-$p^2$ series is organised by subgraphs — the diagram itself, one-line removals, two-line removals, and the vacuum diagram — giving a direct correspondence between each series and a region of the loop-momentum integration.
- The numerical table comparing two-dimensional integration, the hypergeometric series, a Taylor expansion and the one-dimensional representation provides cross-validation that any follow-up calculation can reuse.
Reading between the lines
- The one-dimensional representation is the piece most likely to outlive the paper: because the integrand is elementary, it can be pushed to higher precision and to complex $p^2$ (timelike and spacelike) without re-deriving series, which is what a full electroweak two-loop calculation would actually need.
- The elliptic-integral results suggest a structural statement the authors do not make explicitly: for these topologies the imaginary part lives in a two-dimensional space of elliptic periods, so any threshold expansion should be expressible as a sum over those periods rather than as a generic hypergeometric series.
- Since the master diagram is excluded precisely because it lacks a self-energy subloop, a natural extension is to look for a topology where a two-loop insertion plays the role that $B_0$ plays here — the same dispersion-plus-partial-fraction trick would then apply one level up.
- The agreement in Table 1 between four independent methods is a template: any new method for massive two-loop diagrams can be benchmarked against these numbers, which makes the paper useful as a test set even to readers uninterested in the analytic forms.
Original abstract
Motivated by the precision results in the electroweak theory studies of two-loopFeynman diagrams are performed. Specifically this paper gives a contribution to the knowledge of massive two-loop self-energy diagrams in arbitrary and especially four dimensions.This is done in three respects firstly results in terms of generalized, multivariable hypergeometric functions are presented giving explicit series for small and large momenta. Secondly the imaginary parts of these integrals are expressed as complete elliptic integrals.Finally one-dimensional integral representations with elementary functions are derived.They are very well suited for the numerical evaluations.
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
Motivated by the precision results in the electroweak theory studies of two-loopFeynman diagrams are performed. Specifically this paper gives a contribution to the knowledge of massive two-loop self-energy diagrams in arbitrary and especially four dimensions.This is done in three respects firstly results in terms of generalized, multivariable hypergeometric functions are presented giving explicit series for small and large momenta. Secondly the imaginary parts of these integrals are expressed as complete elliptic integrals.Finally one-dimensional integral representations with elementary functions are derived.They are very well suited for the numerical evaluations.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Motivated by the precision results in the electroweak theory studies of two-loopFeynman diagrams are performed. | background 0.80 | 0.65 | 0.05 | asserted 0.79 |
| s1 | Specifically this paper gives a contribution to the knowledge of massive two-loop self-energy diagrams in arbitrary and especially four dimensions.This is done in three respects firstly results in terms of generalized, multivariable hypergeometric functions are presented giving explicit series for small and large momenta. | contribution 0.99 | 0.92 | 0.29 | asserted 1.00 |
| s2 | Secondly the imaginary parts of these integrals are expressed as complete elliptic integrals.Finally one-dimensional integral representations with elementary functions are derived.They are very well suited for the numerical evaluations. | result 0.48 | 0.95 | 0.19 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v2
- full text
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- references and citing sentences
- relations to other papers
- P abstract
- S sections
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- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-ph/9409388 by the authors.
References
How the literature uses it
51 arXiv papers cite this in 57 sentences
Papers citing it · 25 sentences without a confident label
Uses its method or tool 7 papers
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The two-loop self-energy integrals needed for the renormalization procedure and the vertex integrals with self-energy sub-loops have been computed using the dispersion relation technique described in Refs. [ref] .
Complete electroweak two-loop corrections to Z boson production and decay · Calculation of two-loop vertex corrections · 1.00
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We evaluate these two-loop integrals using the numerical dispersion integral technique [ref] (see also Refs. [ref] ).
Parity-Violating M{\o}ller Scattering at NNLO: Closed Fermion Loops · Method · 1.00
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Two-loop self-energy integrals and vertex integrals with self-energy subloops have been computed using the dispersion relation techniques described in Refs. [ref] .
The two-loop electroweak bosonic corrections to $\sin^2\theta_{\rm eff}^{\rm b}$ · Strictly numerical two-loop integration techniques · 0.99
Uses its data or values 1 paper
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Also all $$-divergent parts and a few finite parts of the two-loop integrals appearing in the calculation are known from Refs. [ref] .
Evaluation of multi-loop multi-scale integrals and phenomenological two-loop applications · Analytically known integrals · 0.85
Cites it as background 23 papers
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These integrals have long been known to involve elliptic curves [ref] .
Cuts and Isogenies · Introduction · 0.94
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It is now time to introduce the two-loop sunset integral [ref] .
A walk on sunset boulevard · The two-loop sunset integral · 0.98
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Many procedures for a precise evaluation of the Master Integrals (MI's) can be found in the literature [ref] .
BOKASUN: a fast and precise numerical program to calculate the Master Integrals of the two-loop sunrise diagrams · Introduction · 0.98
Discussion
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