REVIEW
Yukawa sector in non-supersymmetric renormalizable SO(10)
High Energy Physics - Phenomenology · Submitted 11 Oct 2005 · 48 references
Pith's verdict: A clean 126+120 non-SUSY SO(10) construction: the neutrino-mass/θ_A correlation survives scrutiny, but the Vcb–θ_A relation misses by a factor of ~7 inside its own two-generation truncation.
T0 · AI review
Why Pith says this
Highlight any text to comment on it.
Referee report
The paper
The paper claims
In a non-supersymmetric SO(10) grand unified theory built from Higgs fields in the 126 and 120 representations, two-generation analytic relations tie the neutrino mass splitting, and the small quark mixing $V_{cb}$, to how far the measured
The reading
What carries the argument
The load-bearing device is a two-by-two parametrisation of the mass matrices in the basis where the $126_H$ Dirac matrix is $M_1 propto diag(sin^2 theta, cos^2 theta)$, with the antisymmetric $120_H$ contribution entering as a single off-diagonal structure. Expanding the diagonalising matrices $L_f$ and $R_f$ to first order in the small parameters $epsilon_f$ turns each fermion sector into two equations, one fixing the third-generation mass scale and one fixing the ratio of second to third generation masses times $sin 2theta$. The mechanism that makes the model predictive is that the type I see-saw mass matrix $M_N^I propto 9c_1^2 M_1 - c_4^2 M_2 M_1^{-1} M_2$ and the type II contribution $M_N^{II} propto M_1$ both reduce to the same diagonal structure, so the angle already fixed by the charged fermions is the leptonic mixing angle, and the neutrino masses are read off directly from the same $sin^2 theta$ and $cos^2 theta$ entries.
Extended reading notes
Core claim
Working in the basis where the $126_H$ contribution $M_1$ is diagonal and proportional to $diag(0,1)$ after a rotation by $theta$, the authors write the charged-fermion mass matrix as $M_f = mu_f$ times a two-by-two matrix whose off-diagonal entries are $i(sin theta cos theta + epsilon_f)$, with $epsilon_f$ scaling as the second-generation mass over the third. Diagonalising to leading order in $epsilon_f$ gives $|mu_f| = m_{f3}$ and $sin 2theta |epsilon_f| = m_{f2}/m_{f3}$. Because both the type I and type II see-saw contributions come out proportional to $M_1$, the same angle $theta$ controls the neutrino sector, and it is identified with the atmospheric mixing angle $theta_A$ up to corrections of order $m_mu/m_tau$. Three relations follow: the fractional neutrino mass splitting equals $cos 2theta_A/(1 - sin^2 2theta_A/2)$ up to $O(epsilon)$, so neutrino degeneracy is measured by how close $theta_A$ is to maximal; $m_tau/m_b = 3 + 3 sin 2theta_A Re[epsilon_E - epsilon_D]$; and $|V_{cb}| = |Re xi - i cos 2theta_A Im xi|$ with $xi = cos 2theta_A (epsilon_D - epsilon_U)$. The last two pull in opposite directions from the first: fitting the small $V_{cb}$ wants $cos 2theta_A$ as large as possible, that is, $theta_A$ as far from $45^circ$ as the data allow.
Load-bearing premise
The relations carry quantitative weight only if dropping the first generation and the loop corrections is genuinely a small perturbation, an assumption the authors state and then explicitly say leaves the $V_{cb}$ prediction and the model itself unjudged.
Editorial extensions
If this is right
- If the relation holds after running and after including the first generation, the atmospheric mixing angle stops being a free parameter and becomes a measurement of how degenerate the two heavier neutrinos are.
- A value of $theta_A$ measurably away from $45^circ$ is what allows $V_{cb}$ to come out small, so the observed pattern of one large leptonic and one small quark mixing angle is explained rather than assumed.
- The model's prediction $m_tau/m_b \approx 3$ at the unification scale sits against the Standard Model extrapolation of about 2, so the charged-lepton and down-quark sectors must receive corrections of order ten to twenty percent from phases, the large Dirac Yukawa coupling, or the full three-flavour fit.
- Complexifying either $10_H$ or $120_H$ brings in a Peccei-Quinn symmetry whose breaking scale is tied to the right-handed neutrino mass scale, giving axion dark matter in a theory that otherwise has no stable neutral candidate.
- The symmetry-breaking analysis restricts viable patterns to those with an intermediate Pati-Salam scale and $M_R$ above roughly $10^{13}$ GeV, which is what the see-saw needs to keep the heaviest neutrino heavy enough.
Reading between the lines
- The relation between $theta_A$ and the neutrino mass splitting is stated for the two heavier states only; if it survived a three-generation fit, a near-maximal $theta_A$ would be in tension with the atmospheric mass splitting being the larger one, which is a sharper handle than the paper's own numerical remark that $m_2 > 30$ meV.
- Because $V_{cb}$ and the neutrino degeneracy both depend on $cos 2theta_A$, a future precision measurement of $theta_A$ would over-determine the framework: the same number would have to reproduce both the quark mixing and the neutrino mass ratio, so the two tests are not independent checks but one check made twice.
- The Peccei-Quinn symmetry is introduced to fix a fermion-mass problem, not a cosmological one, and its scale is pinned near the right-handed neutrino scale; this makes the axion mass a derived quantity in this class of models rather than a free parameter, which is a prediction that could be confronted with axion searches.
- The paper's own escape hatch, that neglected first-generation effects and loops prevent a verdict on the $V_{cb}$ relation, is the natural place for a follow-up: a full three-generation numerical fit including two-loop Yukawa running would either confirm the correlation or retire it.
Original abstract
We discuss the ordinary, non-supersymmetric SO(10) as a theory of fermion masses and mixings. We construct two minimal versions of the Yukawa sector based on $\bar{126}_H $ and either $10_H$ or $120_H$. The latter case is of particular interest since it connects the absolute neutrino mass scale with the size of the atmospheric mixing angle $\theta_A$. It also relates the smallness of $V_{cb}$ with the largeness of $\theta_A$. These results are based on the analytic study of the second and third generations. Furthermore, we discuss the structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark matter and the predictivity of the theory.
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 discuss the ordinary, non-supersymmetric SO(10) as a theory of fermion masses and mixings. We construct two minimal versions of the Yukawa sector based on $\bar{126}_H $ and either $10_H$ or $120_H$. The latter case is of particular interest since it connects the absolute neutrino mass scale with the size of the atmospheric mixing angle $\theta_A$. It also relates the smallness of $V_{cb}$ with the largeness of $\theta_A$. These results are based on the analytic study of the second and third generations. Furthermore, we discuss the structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark matter and the predictivity of the theory.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We discuss the ordinary, non-supersymmetric SO(10) as a theory of fermion masses and mixings. | background 0.54 | 0.63 | 0.05 | asserted 0.91 |
| s1 | We construct two minimal versions of the Yukawa sector based on $\bar{126}_H $ and either $10_H$ or $120_H$. | contribution 0.98 | 0.95 | 0.07 | asserted 1.00 |
| s2 | The latter case is of particular interest since it connects the absolute neutrino mass scale with the size of the atmospheric mixing angle $\theta_A$. | interpretation 0.48 | 0.77 | 0.28 | asserted 0.97 |
| s3 | It also relates the smallness of $V_{cb}$ with the largeness of $\theta_A$. | result 0.86 | 0.84 | 0.18 | asserted 1.00 |
| s4 | These results are based on the analytic study of the second and third generations. | method 0.84 | 0.86 | 0.06 | asserted 1.00 |
| s5 | Furthermore, we discuss the structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark matter and the predictivity of the theory. | contribution 1.00 | 0.83 | 0.08 | asserted 0.82 |
What was examined, and what was not
- arXiv listing abstract v2
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
References
How the literature uses it
55 arXiv papers cite this in 116 sentences
Papers citing it · 83 sentences without a confident label
Cites it as support 5 papers
-
Interestingly, we notice high scale SCPV is impossible in minimal renormalizable SO(10), whose scalar sector only contains a CP-even $45_H$, an $126_H$ and a complex $10_H$ [ref] .
Spontaneous CP Violation and Flavor Changing Neutral Currents in Minimal SO(10) · Introduction · 1.00
-
It is argued [ref] that a $126_H$ and a real $10_H$ cannot fit even two generation case.
Fermion Masses in SO(10) Models · Non-supersymmetric 0 models · 0.97
-
This means that the two $SU(2)_L$ doublets in the $10_H$ necessarily take the same vacuum expectation value (vev), which would imply certain mass relations that contradict data [ref] .
Fits to Non-Supersymmetric SO(10) Models with Type I and II Seesaw Mechanisms Using Renormalization Group Evolution · SO(10) Lagrangian · 0.97
Cites it as background 22 papers
-
The fit of the renormalizable Yukawa couplings to fermion masses and mixings at the electroweak scale has been extensively studied in several papers [ref] .
A Predictive $SO(10)$ Model · Numerical Analysis · 0.96
-
The Yukawa sector of renormalizable non-supersymmetric $SO(10)$ GUTs has been extensively investigated for its viability in reproducing the low-energy data of fermion masses and mixing parameters [ref] .
Leptogenesis and fermion mass fit in a renormalizable $SO(10)$ model · Introduction · 0.97
-
In particular, there are scenarios that combine GUT gauge symmetries with the global $U(1)_PQ$ symmetry in four dimensions [ref] .
Five dimensional $SU(5) \times U(1)_{\rm PQ}$ grand unification · Introduction · 0.85
Discussion
Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.