arXiv subjects

Tsutomu T. Yanagida

Publications and source records attributed to Tsutomu T. Yanagida.

At least 37 records · Page 2Linked to original sources

arXiv2025

GUT-motivated non-invertible symmetry as a solution to the strong CP problem and the neutrino CP-violating phase

The unsuppressed CP violation in QCD is a problem in the standard model. If we have some mechanism to guarantee real determinants of the quark mass matrices, the vanishing physical vacuum angle $\bar θ$ indicates the CP invariance at the fundamental level. Thus, the small ${\bar θ}$ is technically natural, since we have an enhanced CP symmetry in the limit of the vanishing $\bar θ=0$. In fact, it was proved that the vacuum angle is never renormalized up to the four-loop level once it is fixed at 0 value at some high energy scale. The purpose of this paper is to construct a model which guarantees the real determinants of the quark mass matrices assuming a non-invertible symmetry.

hep-ph↗

arXiv2025

Axionless Solution to the Strong CP Problem -- two-zeros textures of the quark and lepton mass matrices and neutrino CP violation --

CP invariance is a very attractive solution to the strong CP problem in QCD. This solution requires the vanishing ${\rm arg}\,[{\rm det}\, M_d\, {\rm det} M_u]$, where the $M_d$ and $M_u$ are the mass matrices for the down- and up-type quarks. It happens if we have several zeros in the quark mass matrices. We proceed a systematic construction, in this paper, of two zeros textures for the down-type quark mass matrix while the mass matrix for the up-type quarks is always diagonal. We find only three types of the mass matrices can explain the observed CKM matrix, the masses of the quarks and the charged leptons and the small enough vacuum angle $θ< 10^{-10}$. We extend the mass construction to the neutrino sector and derive predictions on the CP violating parameter $δ_{CP}$ in the neutrino oscillation and the mass parameter $m_{ββ}$. It is extremely remarkable that the normal (NH) and inverted (IH) hierarchies in the neutrino masses are equally possible in the case where we introduce only two right-handed neutrinos $N$s. Furthermore, we have a strict prediction on the $δ_{CP} \simeq 200^\circ$ or $250^\circ$ in the NH case. If it is the case we can naturally explain the positive sign of the baryon asymmetry in the present universe.

hep-ph↗

arXiv2025

Non-invertible Symmetry as a Solution to the Strong CP Problem in a GUT-inspired Standard Model

We propose a three-zero texture for the down-quark mass matrix within a $SU(5)$ GUT-inspired Standard Model, enforced by a non-invertible selection rule originating from $\mathbb{Z}_2$ gauging of $\mathbb{Z}_N$ symmetries. Assuming CP invariance at the high-energy scale, our framework solves the strong CP problem while reproducing a realistic quark mass matrix. The CP symmetry is spontaneously broken down at an intermediate scale via complex vacuum expectation values of new scalar fields $η_i$, which generate the CP phase in the CKM matrix without inducing the QCD $\barθ$ term. The present model incorporates three generations of matter, Higgs, and additional scalars with a common structure under the non-invertible symmetry, which may be naturally embedded into $SO(10)$ GUTs at high energies.

hep-ph↗

arXiv2025

Dynamical dark energy in the no-scale Brans-Dicke gravity

We add a new scalar field in the no-scale Brans-Dicke gravity and require it to have a global O(2) symmetry with the original scalar field in the Brans-Dicke gravity. This gives us a new massless scalar field in the Einstein frame due to the SO(2) symmetry. We then explicitly break the O(2) symmetry to a $D_4$ symmetry, and this scalar field gains a periodic potential. This scalar field can serve as the quintessence field to explain dark energy. If we further add the $R^2$ term and the non-minimal coupling to the Higgs field, we can realize inflation and reheating, and this leads to a super-Planckian decay constant of the quintessence potential. The super-Planckian decay constant is consistent with the newly released observational data according to a recent analysis.

hep-ph↗

arXiv2025

Non-invertible symmetry as an axion-less solution to the strong CP problem

We use a non-invertible symmetry to construct a three-zero texture for the down-type quark mass matrix, which can resolve the strong CP problem without invoking the axion, in four-dimensional spacetime with three quark families in QCD. We assume CP invariance at the fundamental high-energy scale.

hep-ph↗

arXiv2025

Dark Matter in the High-Scale Seesaw Leptogenesis Paradigm

The seesaw mechanism with three heavy Majorana right-handed neutrinos provides an elegant explanation for neutrino masses and, combined with leptogenesis, can generate the baryon asymmetry of the universe (BAU). Naturally embedded in a Grand Unified Theory, this framework stands as one of the best-motivated extensions beyond the Standard Model, but it is very difficult to test it. Moreover, it does not account for dark matter (DM). In this paper, we propose a minimal extension that introduces a dark sector with a singlet Majorana fermion (as the DM candidate) and a complex scalar singlet. The heavy right-handed neutrinos serve another role beyond generating neutrino masses and the BAU: producing the cold DM density through their decays. Interestingly, the model also predicts a subdominant DM component from late scalar decays, which in some cases may be hot or warm at the onset of structure formation, as well as an equal number of non-thermal neutrinos. These components leave distinct signatures in various cosmological observables. Furthermore, electromagnetic energy injection from scalar decays alter predictions from Big Bang Nucleosynthesis and induce spectral distortions in the Cosmic Microwave Background black-body spectrum. In this context, upcoming experiments, such as the Primordial Inflation Explorer (PIXIE), could probe the mechanism of neutrino mass generation.

hep-ph↗

arXiv2025

Induced Gravitational Waves probing Primordial Black Hole Dark Matter with Memory Burden

Quantum evaporation of a black hole is conventionally studied semiclassically by assuming self-similarity of the black hole throughout the evaporation process. However, its validity was recently questioned, and the lifetime of a black hole is conjectured to be much extended by the memory burden effect. It gives rise to the possibility that the primordial black holes (PBHs) lighter than $10^{10}$ grams are the dark matter in the Universe. To probe such PBH dark matter, we study gravitational waves (GWs) induced by primordial curvature perturbations that produced the PBHs. We find $Ω_\text{GW}(f_\text{peak})h^2 = 7 \times 10^{-9}$ with the peak frequency $f_\text{peak} = 1\times 10^{3} \, (M_\text{PBH}/(10^{10}\,\mathrm{g}))^{-1/2}\, \mathrm{Hz}$, and the induced GWs associated with the PBH dark matter whose initial mass is greater than about $10^7$ grams can be tested by future observations such as Cosmic Explorer. Furthermore, the scenario can be in principle confirmed by detecting another GW signal from the mergers of PBHs, which leads to high-frequency GWs with $f_\text{peak} = 2 \times 10^{27}\, (M_\text{PBH, ini}/(10^{10}\, \mathrm{g}))^{-1} \, \mathrm{Hz} $. On the other hand, the induced GW signals stronger than expected would contradict the dark matter abundance and exclude the memory burden effect.

astro-ph.CO↗

arXiv2025

Féeton ($B-L$ Gauge Boson) Dark Matter Testable in Future Direct Detection Experiments

In this paper, we revisit the féeton (gauge boson of $U(1)_{B-L}$ symmetry) dark matter scenario, and first point out the $U(1)$ gauge symmetry can be a linear combination of the $B-L$ and the SM hypercharge gauge symmetries. With the redefinition of $B-L$ charge of fermions, the coupling between electron and féeton can be enhanced. After showing the parameter space required from the DM stability and cosmic production, we discuss the potential for verifying them in dark matter direct detection experiments. The results show that future experiments, such as SuperCDMS, have a sensitivity to reach the féeton DM region consistent with its cosmic production.

hep-ph↗

arXiv2025

Detecting a Fifth-Force Gauge Boson via Superconducting Josephson Junctions

A new fifth force between particles carrying $B-L$ charges is well-motivated by the intriguing $U(1)_{B-L}$ extension of the standard model. The gauge boson mediator, Féeton, also serves as a dark matter candidate. In this letter, we propose a novel experimental design to detect the quantum phase difference caused by this fifth force using a superconducting Josephson junction. We find that the experiment has the best sensitivity to the gauge coupling when the gauge boson is within the mass range of $0.01\,$eV to $10\,$eV, which is an interesting mass region for the Féeton dark matter. This opens up a new avenue for the measurement of new physics at small scale below millimeter.

hep-ph↗

arXiv2025

Dark Matter Annihilation via Breit-Wigner Enhancement with Heavier Mediator

We propose a new scenario that both the dark matter freeze-out in the early Universe and its possible annihilation for indirect detection around a supermassive black hole are enhanced by a Breit-Wigner resonance. With the mediator mass larger than the total initial dark matter mass, this annihilation is almost forbidden at late times. Thus, the stringent cosmic microwave background and indirect detection constraints do not apply. However, a supermassive black hole can accelerate the dark matter particles to reactivate this resonant annihilation whose subsequent decay to photons leaves a unique signal. The running Fermi-LAT and the future COSI satellites can test this scenario.

hep-ph↗

arXiv2025

Proposal for a Quantum Mechanical Test of Gravity at Millimeter Scale

The experimental verification of the Newton law of gravity at small scales has been a longstanding challenge. Recently, torsion balance experiments have successfully measured gravitational force at the millimeter scale. However, testing gravity force on quantum mechanical wave function at small scales remains difficult. In this paper, we propose a novel experiment that utilizes the Josephson effect to detect the different evolution of quantum phase induced from the potential difference caused by gravity. We demonstrate that this experiment can test gravity quantum mechanically at the millimeter scale, and also has a potential to investigate the parity invariance of gravity at small scales.

hep-ph↗

arXiv2024

Prediction of the CP Phase $δ_{CP}$ in the Neutrino Oscillation and an Axion-less Solution to the Strong CP Problem

A model of the axion-less solution to the strong CP problem has been recently constructed based on the $\bf T^2/\mathbb{Z}_3$ orbifold in the six dimensional space-time. We extend, in this paper, the model to include the lepton sector with three right-handed neutrinos. A crucial point in the extended model is that we have only one CP-violating phase and thus the CP phase in the neutrino oscillation can be predicted by the CP phase in the CKM matrix. The CP phase $δ_{CP}$ in the PMNS matrix is predicted as $δ_{CP}\simeq 192^\circ - 195^\circ$ which can be tested in the near future experiments. We also discuss the effective mass $m_{ββ}$ responsible for the neutrino-less double beta decay of nucleus, which is predicted as $m_{ββ} \simeq 8-11$\,meV. We consider the leptogenesis and confirm that our model generates the right sign of the baryon asymmetry if the first family right-handed neutrino is the lightest among the heavy right-handed neutrinos.

hep-ph↗

arXiv2024

Large CP Violation from the Minimum Seesaw Model

The minimum seesaw model with two right-handed neutrinos is considered, where the lightest neutrino is naturally massless. Instead of adopting texture zeros in the lepton Yukawa matrices, which cause both theoretical and experimental troubles, here we propose two-$\boldsymbolε$ textures, where $\boldsymbolε$ is a small number. Combined with neutrino oscillation experimental data, we find that a large CP angle is preferred for the normal neutrino mass order. In contrast, the CP angle almost vanishes for the inverted order. This can be well-tested in near-future experiments, such as Hyper-Kamiokande. Besides, the predicted effective Majorana neutrino mass $m_{ee}$ and the total neutrino mass $\sum m^ν_i$ are also within reach of ongoing or future experiments.

hep-ph↗

arXiv2024

Do neutrinos bend? Consequences of an ultralight gauge field as dark matter

An ultralight gauge boson could address the missing cosmic dark matter, with its transverse modes contributing to a relevant component of the galactic halo today. We show that, in the presence of a coupling between the gauge boson and neutrinos, these transverse modes affect the propagation of neutrinos in the galactic core. Neutrinos emitted from galactic or extra-galactic supernovae could be delayed by $δt = \left(10^{-8}-10^1\right)\,$s for the gauge boson masses $m_{A'} = \left(10^{-23}-10^{-19}\right)\,$eV and the coupling with the neutrino $g= 10^{-27}-10^{-20}$. While we do not focus on a specific formation mechanism for the gauge boson as the dark matter in the early Universe, we comment on some possible realizations. We discuss model-dependent current bounds on the gauge coupling from fifth-force experiments, as well as future explorations involving supernovae neutrinos. We consider the concrete case of the DUNE facility, where the coupling can be tested down to $g \simeq 10^{-27}$ for neutrinos coming from a supernova event at a distance $d = 10\,$kpc from Earth.

hep-ph↗

arXiv2024

Three-zero texture of quark-mass matrices as a solution to the strong CP problem

The strong charge-parity (CP) problem has been a long-standing problem in particle physics since 1976, illustrating the small CP-violation phase in quantum chromodynamics (QCD). The axion, based on the Peccei-Quinn mechanism, is the most popular solution to the problem. In this paper, we propose an alternative solution based on the three-zero texture of quark mass matrices without additional heavy quark states, which has been shown to fit data well. We show that the required three-zero texture is naturally constructed in a six-dimensional spacetime with a $\mathbf{T}^2/\mathbb{Z}_3$ orbifold compactification.

hep-ph↗

arXiv2024

Féeton dark matter above the $e^-e^+$ threshold

The new gauge boson introduced in the minimal extension of the standard model (SM) by gauging the U(1)$_{\rm B-L}$ symmetry plays the role of dark matter when the U(1)$_{\rm B-L}$ gauge coupling is highly suppressed. This dark matter, named the Féeton dark matter is known to be efficiently created in the early universe by inflationary fluctuations with minimal gravity coupling, hence the framework, the gauged U(1)$_{\rm B-L}$ extended SM + inflation, solves the four major problems of the SM; neutrino masses/mixings, dark matter, baryon asymmetry of the universe, and the initial condition of the universe (inflation). We comprehensively study the phenomenology of the dark matter when it is heavier than the $e^- e^+$ threshold, namely twice the electron mass, considering the threshold effect on the dark matter decay into $e^- e^+$. The viable parameter region is found only in the threshold region, while the branching fraction of the decay into $e^- e^+$ (i.e., the $e^- e^+$ signal) never vanishes even at the threshold due to the effect. As a result, the pure U(1)$_{\rm B-L}$ extension without the kinetic mixing between the U(1)$_{\rm B-L}$ and hyper-charge gauge bosons have already been excluded by the present observation of the 511\,keV photon from the galactic center. So, the Féeton dark matter requires a non-zero kinetic mixing to be a viable dark matter candidate and will be efficiently explored by future MeV-gamma ray telescopes thanks to the non-vanishing decay process into $e^- e^+$.

hep-ph↗

arXiv2024

Axion Detection Experiments Meet the Majoron

The majoron is a well-motivated light (pseudo-Nambu-Goldstone) boson associated with the spontaneous breaking of a global lepton-number symmetry. In this {\it letter}, we relate the spontaneous breaking scale and its soft-breaking mass by requiring that the majoron is the main component of the dark matter. An electromagnetic-anomalous coupling can be induced by minimally modifying the original majoron model, surprisingly, predicting a parameter region that largely overlaps with the QCD-axion dark matter band. Thus, we expect that axion search experiments meet the majoron.

hep-ph↗

arXiv2024

Thermal Relic Right-Handed Neutrino Dark Matter

It is known that two heavy Majorana right-handed neutrinos are sufficient to generate the baryon asymmetry in the present universe. Thus, it is interesting to identify the third right-handed neutrino $N$ with the dark matter. We impose a new discrete symmetry $Z_2$ on this dark matter neutrino to stabilize it. However, the $U(1)_{B-L}$ gauge boson $A'$ couples to the right-handed neutrino $N$. If the $B-L$ breaking scale $V_{B-L}$ is sufficiently low, the dark matter neutrino $N$ can be in the thermal bath. We find that the thermal relic $N$ can explain the dark matter abundance for the $B-L$ breaking scale $ V_{B-L} \sim O(10)\,$TeV. After considering all the constraints from the existing experiments, a narrow mass region of the thermal produced right-handed neutrino dark matter $N$ is still surviving.

hep-ph↗