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Yukawa and Tri-scalar Processes in Electroweak Baryogenesis

High Energy Physics - Phenomenology · Submitted 8 Mar 2006 · 37 references

Pith's verdict: New decay/inverse-decay Yukawa rates and the breakdown of the fast-ΓY approximation are real, but the 20–100% Y_B claims rest on an unclosed transport system and an untested supergauge assumption.

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arXiv IDhep-ph/0603058 (version 2)
Pith IDHR2AQX4X, Pith's permanent record of this paper and its review
CitationChristopher Lee, Michael J. Ramsey-Musolf, Sean Tulin, Vincenzo Cirigliano. "Yukawa and Tri-scalar Processes in Electroweak Baryogenesis." arXiv:hep-ph/0603058 (2006). https://pith.science/paper/HR2AQX4X
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The paper

The paper claims

Decays, not scatterings, dominate the Yukawa transport rate that feeds MSSM electroweak baryogenesis.

The reading

This paper derives the contributions that top-quark Yukawa and tri-scalar interactions make to the quantum transport equations of electroweak baryogenesis in the Minimal Supersymmetric Standard Model (MSSM), the equations that track particle densities as bubbles of broken electroweak symmetry expand through the plasma. It shows that decays and inverse decays of squarks, quarks, Higgs scalars, and Higgsinos contribute to the Yukawa transport coefficient $\Gamma_Y$ — the rate at which Higgs-supermultiplet densities are converted into quark-supermultiplet densities — at zeroth order in the strong coupling, and that these contributions can be substantially larger than the $O(\alpha_s)$ scattering terms that earlier treatments assumed dominate. It further argues that the usual fast-$\Gamma_Y$ approximation breaks down for realistic MSSM parameters, because the chiral relaxation rates in the bubble wall are comparable to or larger than $\Gamma_Y$. Solving the transport equations numerically, it finds that keeping $\Gamma_Y$ finite raises the baryon-to-entropy ratio $Y_B$ by 20% in the resonant regime and up to 100% in the nonresonant regime relative to the $\Gamma_Y \to \infty$ limit. The result matters because a quantitative link between baryogenesis and electric-dipole-moment experiments depends on getting these transport rates right.

What carries the argument

The central object is the Closed Time Path (CTP) Schwinger-Dyson formulation of quantum transport, applied to three-body source terms through the rate functions $I_B$ (tri-scalar decays) and $I_F$ (Yukawa decays). These integrals encode thermally averaged decay, emission, and absorption rates with all mass-threshold and Bose/Fermi distribution structure, and they are what determine whether the $O(\alpha_s^0)$ channels are kinematically open; they enter the transport equations through $\Gamma_Y$ and $\bar{\Gamma}_Y$ in Eqs. (40a)-(40b). The reduction to a closed set of equations uses the chemical-potential equalities enforced by fast gauge and gaugino interactions, including the supergauge equilibrium condition $\mu_H = \mu_{\widetilde H}$ of Eq. (37), which lets Higgs and Higgsino densities be combined into the reduced set $(T,Q,H,h)$.

Extended reading notes

Core claim

On this paper's own terms, the central discovery is a hierarchy reversal in the transport equations: the coefficient $\Gamma_Y$ that couples Higgs-supermultiplet densities to third-generation quark-supermultiplet densities receives its leading contributions from two-body decay and inverse-decay channels---for example $t_R + \tilde t_L \leftrightarrow H_u^0$ and the analogous superpartner processes---at order $\alpha_s^0$, not from the $O(\alpha_s)$ scattering processes such as $t_R + g \to t_L + H_u^0$ on which earlier treatments focused. The paper derives the rate functions $I_B$ and $I_F$ for tri-scalar and Yukawa three-body sources, builds $\Gamma_Y$ and $\bar{\Gamma}_Y$ from them, and shows that for MSSM parameters consistent with a strong first-order phase transition and precision electroweak data the decay contributions are typically several times larger than the scattering contribution. It also derives the new coefficient $\tilde{\Gamma}_Y$ and shows $|\bar{\Gamma}_Y/\Gamma_Y| < 1/2$, the paper's correction to an earlier equality. Because the relaxation rates $\Gamma_H$ and $\Gamma_M$ computed in the same CTP framework are as large as or larger than $\Gamma_Y$ inside the bubble wall, the $1/\Gamma_Y$ expansion fails; numerically, the finite-$\Gamma_Y$ correction to $Y_B$ is 20% in the resonant case and up to 100% in the nonresonant case.

Load-bearing premise

The load-bearing premise is that gaugino-mediated interactions are fast enough during the phase transition to keep the Higgs scalars and their Higgsino partners in chemical equilibrium with a single chemical potential ($\mu_H = \mu_{\widetilde H}$); the paper explicitly defers a test of this assumption, and if it fails, the reduced transport equations and all numerical baryon-asymmetry results derived from them are not correct.

Editorial extensions

If this is right

  • At MSSM parameter points where the relevant three-body decay channels are kinematically open, previous $O(\alpha_s)$ scattering estimates understate $\Gamma_Y$; when $\Gamma_Y$ is in the realistic few-GeV range, including the decay contributions changes $Y_B$ at the 10\u201320% level.
  • The fast-$\Gamma_Y$ approximation should not be used: the $1/\Gamma_Y$ expansion misses $O(1)$ corrections to the Higgs density $H$, and therefore to $Q$ and $T$, so the transport equations must be solved numerically with finite $\Gamma_Y$.
  • The earlier assumption $|\bar{\Gamma}_Y| = |\Gamma_Y|$ is not correct; for the MSSM parameters considered here $|\bar{\Gamma}_Y/\Gamma_Y| < 1/2$, making the $h/k_h$ term in the transport equations weaker than assumed.
  • In large-$\tan\beta$ scenarios the new coefficient $\tilde{\Gamma}_Y$ and the bottom-quark supermultiplet densities are not suppressed, and the general formulas given in the paper let future calculations include them.

Reading between the lines

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

  • The same $I_B$ and $I_F$ building blocks should transfer to extensions such as the NMSSM or $U(1)^\prime$ models, where a light stop is not needed for the phase transition; in those settings the tri-scalar $A$-dependent part of $\Gamma_Y$ may be relatively more important than in the MSSM benchmark studied here.
  • A spectrum measurement has direct transport consequences: if future colliders place the relevant superpartner masses far from the threshold where the largest mass is just above the sum of the other two, the $O(\alpha_s^0)$ decay contribution is Boltzmann-suppressed and the fast-$\Gamma_Y$ approximation becomes more reliable; measuring the spectrum would therefore test which regime governs baryogen
  • Because finite $\Gamma_Y$ raises $Y_B$ relative to the $\Gamma_Y \to \infty$ limit, the paper's results imply that slightly less CP violation is needed in the Higgs sector to match the observed baryon asymmetry, modestly easing the tension with electron and neutron EDM limits while preserving the conclusion that sleptons must be heavier than about 1 TeV.
Original abstract

We derive the contributions to the quantum transport equations for electroweak baryogenesis due to decays and inverse decays induced by tri-scalar and Yukawa interactions. In the Minimal Supersymmetric Standard Model (MSSM), these contributions give rise to couplings between Higgs and fermion supermultiplet densities, thereby communicating the effects of CP-violation in the Higgs sector to the baryon sector. We show that the decay and inverse decay-induced contributions that arise at zeroth order in the strong coupling, \alpha_s, can be substantially larger than the O(\alpha_s) terms that are generated by scattering processes and that are usually assumed to dominate. We revisit the often-used approximation of fast Yukawa-induced processes and show that for realistic parameter choices it is not justified. We solve the resulting quantum transport equations numerically with special attention on the impact of Yukawa rates and study the dependence of the baryon-to-entropy ratio Y_B on MSSM parameters.

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, 4,421 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.43 · human participants 0.01 · controlled comparison 0.10 · randomized assignment 0.01 · states quantitative result 0.09 · compares with prior results 0.86 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

We derive the contributions to the quantum transport equations for electroweak baryogenesis due to decays and inverse decays induced by tri-scalar and Yukawa interactions. In the Minimal Supersymmetric Standard Model (MSSM), these contributions give rise to couplings between Higgs and fermion supermultiplet densities, thereby communicating the effects of CP-violation in the Higgs sector to the baryon sector. We show that the decay and inverse decay-induced contributions that arise at zeroth order in the strong coupling, \alpha_s, can be substantially larger than the O(\alpha_s) terms that are generated by scattering processes and that are usually assumed to dominate. We revisit the often-used approximation of fast Yukawa-induced processes and show that for realistic parameter choices it is not justified. We solve the resulting quantum transport equations numerically with special attention on the impact of Yukawa rates and study the dependence of the baryon-to-entropy ratio Y_B on MSSM parameters.

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 derive the contributions to the quantum transport equations for electroweak baryogenesis due to decays and inverse decays induced by tri-scalar and Yukawa interactions. contribution 0.99 0.96 0.09 asserted 0.99
s1 In the Minimal Supersymmetric Standard Model (MSSM), these contributions give rise to couplings between Higgs and fermion supermultiplet densities, thereby communicating the effects of CP-violation in the Higgs sector to the baryon sector. interpretation 0.61 0.69 0.12 asserted 1.00
s2 We show that the decay and inverse decay-induced contributions that arise at zeroth order in the strong coupling, \alpha_s, can be substantially larger than the O(\alpha_s) terms that are generated by scattering processes and that are usually assumed to dominate. result 1.00 0.93 0.63 asserted 0.98
s3 We revisit the often-used approximation of fast Yukawa-induced processes and show that for realistic parameter choices it is not justified. result 0.70 0.90 0.12 asserted 1.00
s4 We solve the resulting quantum transport equations numerically with special attention on the impact of Yukawa rates and study the dependence of the baryon-to-entropy ratio Y_B on MSSM parameters. method 0.64 0.97 0.13 asserted 0.97

What kind of paper the classifier reports this is: theoretical result 0.79 · evidence from simulation or computation 0.74.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
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  • 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. FIG. 1: Leading contributions to the self-energies Σ
Figure 2. FIG. 2: Self energies for scalar and fermion fields induced by
Figure 3. FIG. 3: Left panel
Figure 5. illustrate two key points of the Yukawa-induced dynamics: (i) Efficient chargino/neutralino-mediated baryogenesis occurs for ΓY ≫ v 2 w/Dh ∼ 0.0025 GeV, as the Higgs supermultiplet density H injected in the unbroken phase is efficiently converted into LH top-quark density (fueling sphaleron processes) before the bubble catches up. Inclusion of the O(α 0 s ) terms in ΓY affects YB at the 10 − 20% level, as one is already in the plateau region in
Figure 7. FIG. 7: Allowed bands in the
Figure 8. FIG. 8: We plot in the

Showing 6 of the paper's 8 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:hep-ph/0603058 by the authors.

References
How the literature uses it

27 arXiv papers cite this in 64 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 · 36 sentences without a confident label

Contests it 1 paper
  • In addition, the Boltzmann equations of Refs. [ref] follow from Eqs. ([ref],b,[ref]); they too are no longer valid for $τ_yb,τ_yτ ≲τ_diff$.

    Lepton-mediated electroweak baryogenesis · Setting up the Boltzmann equations · contest 0.83

Builds on it 2 papers
  • The plot is based on our recent computation [ref] of the function $F_μ$ in Eq. ([ref]) that builds on our earlier treatment of the quantum transport during a supersymmetric electroweak phase transition [ref] .

    Neutrons and the New Standard Model · EDMs and the Origin of Matter · 0.95

  • Electroweak baryogenesis utilizing these sources in the MSSM has been extensively analyzed in recent studies (e.g. [ref] ), and we build on these analyses in our study of the accidental SUSY scenario.

    Accidental Supersymmetric Dark Matter and Baryogenesis · Introduction · 0.96

Uses its method or tool 10 papers
Uses its data or values 1 paper
Compares with it 2 papers
Cites it as support 1 paper
Cites it as background 7 papers
  • Should one allow for additional source terms, such as non-resonant sources (see e.g. [ref] ) or sources associated with left-right stops, sbottoms or staus (see e.g. [ref] ), all of our conclusions would be weakened.

    Closing in on Supersymmetric Electroweak Baryogenesis with Dark Matter Searches and the Large Hadron Collider · EWB and Bino-like Dark Matter · 0.81

  • As discussed in Refs. [ref] , these scales include a decoherence time, $τ_d$, associated with the departure from adiabatic dynamics; a plasma time, $τ_p$, associated with mixing between degenerate states in the plasma; and an intrinsic quasiparticle evolution time, $τ_int$, associated with the time evolution of a state of a given energy.

    Supergauge interactions and electroweak baryogenesis · Three-body rates: general formalism · 0.81

  • The various issues of calculating the baryon asymmetry of the universe (BAU) in a given particle physics model are a subject of active research (see, for example, [ref] ).

    Beyond MSSM Baryogenesis · Introduction · 1.00

Discussion

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