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Master Formulae for Delta F=2 NLO-QCD Factors in the Standard Model and Beyond

High Energy Physics - Phenomenology · Submitted 26 Feb 2001 · 15 references

Pith's verdict: A solid standard-reference paper: complete analytic NLO ΔF=2 evolution matrices in NDR, with one flagged convention in the ρ-sector that deserves a caution but not alarm.

T0 · AI review

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arXiv IDhep-ph/0102316 (version 1)
Pith IDVNBWGHR6, Pith's permanent record of this paper and its review
CitationAndrzej J. Buras, Joerg Urban, Sebastian Jager. "Master Formulae for Delta F=2 NLO-QCD Factors in the Standard Model and Beyond." arXiv:hep-ph/0102316 (2001). https://pith.science/paper/VNBWGHR6
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Referee report
The paper

The paper claims

The paper supplies closed-form next-to-leading-order QCD evolution matrices for all $Delta F=2$ four-quark operators, so that one universal set of factors carries any model's short-distance Wilson coefficients at the top-mass scale down to,

The reading

The paper sets out to remove a bottleneck in predicting how neutral kaons and neutral $B$ mesons mix. Any model of new physics hands you, at a high scale $mu_t = O(m_t)$, a list of short-distance coefficients $C_i(mu_t)$ for the $Delta F=2$ four-quark operators; experiment, however, lives at scales of 1 to 5 GeV, and the bridge between the two is QCD running. Buras, Jäger and Urban write that bridge down in closed analytic form at next-to-leading order in the strong coupling, for all the chirality sectors of the operator basis, so the same factors serve the Standard Model and every extension of it. They do the same for the separate bridge between lattice matrix elements quoted at 2 GeV and matrix elements at scales below 1 GeV, where hadronic models naturally live. The payoff is a set of master formulae for $Delta M_K$, $Delta M_B$ and $epsilon_K$ in which all model dependence sits in the $C_i(mu_t)$ and all the QCD sits in a handful of universal coefficients.

What carries the argument

The load-bearing object is the evolution matrix written as $hat U(mu_1,mu_2) = (1 + frac{alpha_s(mu_1)}{4pi}hat J) hat U^{(0)} (1 - frac{alpha_s(mu_2)}{4pi}hat J)$ with the leading-order solution $hat U^{(0)} = (alpha_s(mu_2)/alpha_s(mu_1))^{hatgamma^{(0)T}/(2beta_0)}$, built from the one-loop anomalous dimension matrix and the two-loop matrix of the NDR calculation, plus the $hat J$ matrix constructed from the two-loop anomalous dimensions and the $\beta$ function. Because the operators do not mix across chirality sectors, the problem splits into a scalar VLL entry and $2times 2$ matrices for LR and SLL, and crossing quark thresholds is handled by a product of such factors in the $f=5$, $f=4$ and $f=3$ effective theories, with the convention that powers and logarithms of the coupling ratios count as $O(alpha_s^0)$ so that all $O(alpha_s^2)$ terms are consistently dropped. The $rho$ matrices are the same construction run in the opposite direction, from 2 GeV down to $mu_K$, and the scheme-conversion matrices $Delta hat r$ let the results be translated to other renormalization schemes.

Extended reading notes

Core claim

The central claim is that the next-to-leading-order evolution matrices $hat U(mu, mu_t)$ and $hat U(mu_K, mu_L)$ for the $Delta F=2$ dimension-six four-quark operators can be given in explicit closed form in the NDR scheme, for the VLL, LR and SLL sectors (VRR and SRR follow by chirality), with no numerical integration required. Sections 3 and 4 present these as algebraic expressions in the coupling ratios $eta_3$, $eta_4$, $eta_5$ and $tildeeta_4$, separating a leading-order power $eta^P$ from an $O(alpha_s)$ correction; Sections 5 and 6 give numerical tables, the scheme-conversion rules to other renormalization schemes, and the relation to the older $eta_B$ and $eta_2$ factors. The authors report that the running is mild in the vector-vector sector but large in the left-right and scalar sectors: at $mu_K = 1$ GeV the diagonal entry $[eta_{22}]^{LR}$ is enhanced by about a factor of 5.6, $[eta_{11}]^{SLL}$ by about 2.9, while $[eta_{22}]^{SLL}$ is suppressed to about 0.26, and the NLO corrections are typically 5 to 15 percent, reaching about 25 percent for $[eta_{21}]^{LR}$, $[eta_{22}]^{LR}$ and $[eta_{22}]^{SLL}$. Section 7 turns this into master formulae for $Delta M_K$, $Delta M_B$ and $epsilon_K$ in terms of non-perturbative $B_i$ parameters and the Wilson coefficients at $mu_t$, with universal coefficients $P^{VLL}_1 = 0.48$, $P^{LR}_1 = -36.1$, $P^{LR}_2 = 59.3$, $P^{SLL}_1 = -18.1$, $P^{SLL}_2 = -32.2$ in the kaon system.

Load-bearing premise

The left-right $rho$ coefficient in eq. (4.10) contains a term proportional to $log(eta_3)$ that arises only by taking the limit $f to 3$ of the general evolution formula, because the matrix $hat J$ is singular there; the authors classify that limit term as a next-to-leading contribution under their convention, and if that bookkeeping is not the right way to organize the expansion the LR entry of the kaon master formula is mis-assigned.

Editorial extensions

If this is right

  • Once a model's Wilson coefficients $C_i(mu_t)$ are computed in the NDR scheme, $Delta M_K$, $Delta M_B$ and $epsilon_K$ follow directly from the universal $P^a_i$ coefficients, with no further QCD work by the user.
  • In the kaon system the left-right and scalar coefficients are two orders of magnitude larger than the vector-vector one ($P^{LR}_1 = -36.1$, $P^{LR}_2 = 59.3$, $P^{SLL}_1 = -18.1$, $P^{SLL}_2 = -32.2$ against $P^{VLL}_1 = 0.48$), so even small new-physics contributions to those operators can dominate the mixing amplitude.
  • Lattice matrix elements quoted at 2 GeV and hadronic-model matrix elements computed below 1 GeV can be placed on a common scale and compared directly.
  • The familiar Standard Model factors $eta_B$ and $eta_2$ are not the same objects as $[eta(mu_b)]^{VLL}$ and $[eta(mu_K)]^{VLL}$; the paper supplies the explicit conversion between them.
  • The paper also provides the evolution matrix for running upward from $mu_t$ to a higher new-physics scale $mu_s$ in a six-flavour effective theory, so that models with very heavy particles can be matched in stages.

Reading between the lines

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

  • Because the $P^a_i$ are universal numbers, they can be reused as a fixed lookup table by any future model builder; the practical bottleneck then shifts entirely to computing $C_i(mu_t)$ and to the lattice $B$ parameters in the LR and SLL sectors, which Section 7 shows are the least controlled, with scheme shifts of roughly 30 and 20 percent respectively.
  • The size of the LR and SLL enhancements suggests that meson-mixing observables are far more sensitive to chirality-flipped operators than to the standard vector-vector one, which is an argument that a future discrepancy in $epsilon_K$ or $Delta M_K$ would more plausibly point to scalar or left-right new physics than to a shift in the standard operator.
  • The treatment of the $f=3$ limit in the LR sector implies that 'next-to-leading order' in a multi-threshold evolution is partly a bookkeeping convention; two groups using different conventions could legitimately differ at the few-percent level the introduction warns about, without either being wrong.
  • A useful cross-check that the paper does not perform would be to evolve a set of lattice matrix elements from 2 GeV down to 1 GeV and back with the $rho$ matrices and verify closure at the stated accuracy; a failure of closure would localize the problem to a specific sector.
Original abstract

We present analytic formulae for the QCD renormalization group factors relating the Wilson coefficients C_i(mu_t) and C_i(mu), with mu_t = O(m_t) and mu < mu_t, of the Delta F=2 dimension six four-quark operators Q_i in the Standard Model and in all of its extensions. Analogous analytic formulae for the QCD factors relating the matrix elements <Q_i(2 GeV)> and <Q_i(mu_K)> with mu_K < 2GeV are also presented. The formulae are given in the NDR scheme. The strongest renormalization-group effects are found for the operators with the Dirac structures (1 - gamma_5)*(1 + gamma_5) and (1 - gamma_5)*(1 - gamma_5). We calculate the matrix elements <\bar K^0|Q_i|K^0> in the NDR scheme using the lattice results in the LRI scheme. We give expressions for the mass differences Delta M_K and Delta M_B and the CP-violating parameter epsilon_K in terms of the non-perturbative parameters B_i and the Wilson coefficients C_i(mu_t). The latter summarize the dependence on new physics contributions.

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, 5,732 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.13 · human participants 0.01 · controlled comparison 0.02 · randomized assignment 0.01 · states quantitative result 0.12 · compares with prior results 0.20 · mentions code or data availability 0.02.

The abstract, sentence by sentence

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

We present analytic formulae for the QCD renormalization group factors relating the Wilson coefficients C_i(mu_t) and C_i(mu), with mu_t = O(m_t) and mu < mu_t, of the Delta F=2 dimension six four-quark operators Q_i in the Standard Model and in all of its extensions. Analogous analytic formulae for the QCD factors relating the matrix elements <Q_i(2 GeV)> and <Q_i(mu_K)> with mu_K < 2GeV are also presented. The formulae are given in the NDR scheme. The strongest renormalization-group effects are found for the operators with the Dirac structures (1 - gamma_5)*(1 + gamma_5) and (1 - gamma_5)*(1 - gamma_5). We calculate the matrix elements <\bar K^0|Q_i|K^0> in the NDR scheme using the lattice results in the LRI scheme. We give expressions for the mass differences Delta M_K and Delta M_B and the CP-violating parameter epsilon_K in terms of the non-perturbative parameters B_i and the Wilson coefficients C_i(mu_t). The latter summarize the dependence on new physics contributions.

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 present analytic formulae for the QCD renormalization group factors relating the Wilson coefficients C_i(mu_t) and C_i(mu), with mu_t = O(m_t) and mu < mu_t, of the Delta F=2 dimension six four-quark operators Q_i in the Standard Model and in all of its extensions. contribution 1.00 0.95 0.62 asserted 1.00
s1 Analogous analytic formulae for the QCD factors relating the matrix elements <Q_i(2 GeV)> and <Q_i(mu_K)> with mu_K < 2GeV are also presented. contribution 0.96 0.92 0.10 asserted 1.00
s2 The formulae are given in the NDR scheme. method 0.89 0.65 0.05 asserted 1.00
s3 The strongest renormalization-group effects are found for the operators with the Dirac structures (1 - gamma_5)*(1 + gamma_5) and (1 - gamma_5)*(1 - gamma_5). result 0.98 0.87 0.13 asserted 1.00
s4 We calculate the matrix elements <\bar K^0|Q_i|K^0> in the NDR scheme using the lattice results in the LRI scheme. method 0.86 0.93 0.05 asserted 1.00
s5 We give expressions for the mass differences Delta M_K and Delta M_B and the CP-violating parameter epsilon_K in terms of the non-perturbative parameters B_i and the Wilson coefficients C_i(mu_t). contribution 0.65 0.89 0.22 asserted 1.00
s6 The latter summarize the dependence on new physics contributions. interpretation 0.96 0.55 0.10 asserted 0.99

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 1.00.

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 [ηij ]LR factors as functions of µ for α (5) s (MZ) = 0.118. [22℄SLL [21℄SLL [12℄SLL [11℄SLL  [GeV℄ K m L 3 mb 10 30 MW mt 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 -0.5
Figure 2. The [ηij ] SLL factors as functions of µ for α (5) s (MZ) = 0.118 17

Figures reproduced from arXiv:hep-ph/0102316 by the authors.

References
How later papers used it

88 later papers cite it

Evidence: substantial. 71 of the citing papers share no author with it, and 34 of those carry a confident label from Pith's citation classifier.

Pith read 25 of the 164 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

Builds on it 1 of 2 papers with this label · 1 by the same authors

By the same authors

  • Presented an update of the master formula for Delta F=2 processes in LEFT valid in any BSM scenario first presented in this paper.

    SMEFT ATLAS of $\Delta F=2$ Transitions (2020) (same authors) · 0.86 · paraphrased: the licence does not allow quoting

Uses its method or tool 6 of 31 papers with this label · 1 by the same authors

By the same authors

Uses its data or values 2 of 19 papers with this label · 1 by the same authors

By the same authors

How the literature uses it

85 arXiv papers cite this in 159 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 · 91 sentences without a confident label

Builds on it 2 papers
Uses its method or tool 31 papers
  • To compute explicitly the $ΔO_i^NP(x)$ we use the expressions of the observables in terms Wilson Coefficients of dimension-six operators according to the following references: * $ΔB = 2$ and $ΔS=2$ amplitudes: Eqs. (7.24)–(7.27) in Ref. [ref] ; * $ΔC = 2$ amplitude: Eq. (3) in Ref. [ref] ; * $ϵ_K'/ϵ_K$: Eq. (82) in Ref. [ref] , * $ℬ (B→X_sγ)$: Eq. (33) in Ref. [ref] ; * $ℬ (K^+ →π^+ ν̅ ν)$: Eq. (24) in Ref. [ref] [We have contacted the authors and confirmed that the parameter $κ$ should be rescaled by a factor of $(2^3/2 πsin^2θ_W v/α)^2$.].

    Exploring the flavour structure of the high-scale MSSM · Analysis strategy · 1.00

  • The Wilson coefficients are evolved to the low scale $μ_low$ by solving their renormalization group equations [ref] .

    A Supersymmetric Flavor Clockwork · Constraints from Meson Mixing · 0.98

  • [ref] to perform renormalization group evolution of the NP operators $𝒪_1^SLL$, $𝒪_1^SRR$ and $𝒪_2^LR$.

    Flavor Violating Higgs Couplings in Minimal Flavor Violation · Neutral $B$ and $K$ meson mixing · 1.00

Uses its data or values 19 papers
  • Thus, with $ΔM_d^exp=(0.507±0.005) ps^-1$ [ref] and $ΔM_d^SM=(0.560^+0.067_-0.076) ps^-1$ [ref] , using the approximation $|1+δ_d^|≃1+Re δ_d$, we can extract the $1 σ$ range [equation] Similarly, $ΔM_s^exp=(17.77±0.12) ps^-1$ [ref] and $ΔM_s^SM=(17.6^+1.7_-1.8) ps^-1$ [ref] translate into [equation] To proceed, in addition to $m_X^=214.3$ MeV, we use $m_b^=4.4$ GeV, $P_1^VLL=0.84$, $P_1^SLL=-1.47$, $P_1^LR=-1.62$, $P_2^LR=2.46$ [ref] , CKM parameters from Ref. [ref] , $f_B_d=190$ MeV, $f_B_s=228$ MeV, $η_B^=0.551$, $B_B_d=1.17$, and $B_B_s=1.23$ [ref] , as well as meson masses from Ref. [ref] .

    Rare B Decays with a HyperCP Particle of Spin One · Constraints from $B_q$-$B̅_q$ mixing · 0.99

  • In performing the NLO QCD evolutions we have used the $P_a^ij()$ from [ref] , see [ref], which are based on the two-loop anomalous dimensions of operators calculated in [ref] .

    SMEFT ATLAS of $\Delta F=2$ Transitions · The Issue of Evanescent Operators · 0.83

  • The bag parameters at the $μ_b = m_b$ scale are given as [ref] [equation] and the QCD corrections are $η_11 (μ_b)=1.654$ and $η_21 (μ_b)=-0.007$ [ref] .

    Flavor constraints on the Two Higgs Doublet Models of $Z_2$ symmetric and aligned types · Input and experimental data · 1.00

Compares with it 1 paper
Cites it as background 5 papers

Discussion

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