arXiv subjects

Teruyuki Kitabayashi

Publications and source records attributed to Teruyuki Kitabayashi.

At least 19 recordsLinked to original sources

arXiv2026

Leptogenesis via Resonant Sequential Dominance and TBC3 Mixing in a Type-I Seesaw Model

We demonstrate how phenomenological model construction assuming Sequential Dominance can be extended to cases with degenerate right-handed neutrino masses. Because this framework accommodates resonant leptogenesis, we designate it as Resonant Sequential Dominance. We then investigate Dirac mass matrix textures compatible with current neutrino data within Resonant Sequential Dominance, utilizing a novel neutrino mixing matrix ansatz termed TBC3, proposed in this work. Additionally, we present an $A_4 \times (Z_3)^4 \times (Z_2)^2$-symmetric Lagrangian that is consistent with neutrino oscillation data and successfully drives resonant leptogenesis. Lastly, we find that accounting for the observed baryon asymmetry of the Universe requires the lightest right-handed neutrino mass to lie in the range $0.13\text{ TeV} \le m_{N_1} \le 230\text{ TeV}$.

hep-ph↗

arXiv2026

WIMP/FIMP dark matter and primordial black holes with memory burden effect

The lifetime of primordial black holes (PBHs), which formed in the early universe, can be extended by the memory burden effect. Light PBHs may exist today and be candidates for dark matter (DM). We assume that DM is made of thermally produced weakly interacting massive particles (WIMPs), WIMPs produced via the Hawking radiation of PBHs, and PBHs that survived Hawking evaporation via the memory burden effect. Feebly interacting massive particles (FIMPs) are alternatives to WIMPs. Focusing on parameter regions where thermal production dominates and PBHs never dominate the energy density of the Universe, we identify a sufficient condition under which DM particles emitted from PBHs do not thermalize with the thermal bath. In this regime, the total DM relic abundance can be consistently obtained as the sum of the three components. In addition, we show that the contribution from gravitational freeze-in via graviton exchange remains subdominant within the parameter space considered.

hep-ph↗

arXiv2026

Reply to "Comment on `Unified neutrino mixing and approximate $μ-τ$ reflection symmetry'[arXiv:2603.00885]''

Huang and Li [arXiv:2603.00885] have raised the following two points regarding our previous work [arXiv:2502.18029]:(1) The real-value conditions associated with $μ$-$τ$ reflection symmetry were overlooked. (2) Inverted Ordering (IO) remains viable when the latest experimental data are taken into account. As they have pointed out, we overlooked an important real-value condition. However, with regard to point (2), we believe that there may be a misunderstanding. In our original study, we excluded IO based on the constraint on the sum of neutrino masses, $\sum m_ν$. In contrast, they argue that IO remains viable when considering the effective neutrino mass, $|M_{ee}|$. While IO may indeed remain allowed in light of the latest $|M_{ee}|$ data, it is still in tension with the experimental bounds on $\sum m_ν$ under approximate $μ-τ$ symmetry within the discussed model parameter space.

hep-ph↗

arXiv2026

Dirac mass matrix textures and the lightest right-handed neutrino mass scale in Type I seesaw leptogenesis

The type I seesaw mechanism is one of the leading proposed explanations for how neutrinos acquire their tiny masses. However, the mass scale of the undiscovered right-handed neutrinos required by this mechanism remains undetermined. Assuming vanilla leptogenesis in the two-flavor regime, we work backwards to find the required general textures of the Dirac mass matrix from which we determine the mass of the lightest right-handed neutrino to be around $10^9 {\rm GeV}$ to $10^{12} {\rm GeV}$.

hep-ph↗

arXiv2026

Modified TM2 for Reproducing All Best-Fit Values of Neutrino Mixing Angles

As measurements of neutrino mixing angles continue to become more precise, it is increasingly likely that in the very near future a realistic neutrino mixing model will be required to precisely reproduce their best-fit values. In this study, a modified TM$_2$ mixing model which reproduces the best-fit values of all three neutrino mixing angles is proposed. The model reproduces the correct mixing angles within 1$σ$ of the current best-fit values and is robust against any future changes of the best-fit values.

hep-ph↗

arXiv2025

Running scalar spectral index in warm natural inflation

The validity of inflation models is mainly evaluated according to the consistency of the predicted scalar spectral index $n_{\mathrm{s}}$, the tensor scalar ratio $r$, and the running scalar spectral index $α_{\mathrm{s}}$ with cosmic microwave background observations. In warm inflation (WI) scenarios, one can find exact analytical solutions for $α_{\mathrm{s}}$ in principle, but long expressions may be obtained. Previous studies for WI scenarios have only shown approximate analytical solutions or numerical results for $α_{\mathrm{s}}$. In this study, we present a general analytical expression of $α_{\mathrm{s}}$ without approximation in WI. By providing an analytical expression, even if it is mathematically redundant, we believe that $α_{\mathrm{s}}$ will be studied across a broader range of WI models in the future. The obtained analytical expression of $α_{\mathrm{s}}$ is used in the study of warm natural inflation (WNI). Although $n_{\mathrm{s}}$ and $r$ have been previously investigated, $α_{\mathrm{s}}$ is omitted in previous studies on WNI. Our study of $α_{\mathrm{s}}$ completes previous phenomenological studies on WNI. In particular, the lower limit of the symmetry-breaking scale in WNI becomes more concrete in this study.

hep-ph↗

arXiv2025

Interstellar medium gas heating by primordial black holes and dark matter particles

The Leo T dwarf galaxy has been utilized to investigate the heating of interstellar medium gas by both primordial black holes (PBHs) and dark matter (DM) particles. Previous studies have typically assumed that either PBHs or DM particles are responsible for heating the interstellar medium gas. In contrast, this study considers the simultaneous contribution of both PBHs and DM particles to the heating process. If both PBHs and dark photons heat the gas in Leo T, a stringent constraint on the PBH fraction, $f_{\rm PBH}=ρ_{\rm PBH}/ρ_{\rm DM}$ is obtained for $4 \lesssim M_{\rm PBH}/M_\odot \lesssim 10^2$, where $ρ_{\rm PBH}$, $ρ_{\rm DM}$, represent the energy densities of PBHs and DM, respectively, and $M_{\rm PBH}$, and $M_\odot$ denote the masses of PBHs and Sun, respectively. Conversely, if both PBHs and millicharged particles heat the gas, it becomes challenging to impose a more significant constraint on the PBH fraction than previously achieved, due to the very small allowed values of charge parameters within the model.

hep-ph↗

arXiv2025

Scaling in the minimal extended seesaw model

The scaling relations in the two-zero textures of the neutrino mass matrices in the minimal extended seesaw mechanism were discovered by Kumar and Patgiri. We demonstrate that some of these scaling relations can be satisfied without requiring two zero elements in the texture.

hep-ph↗

arXiv2025

Unified neutrino mixing and approximate $μ$-$τ$ reflection symmetry

We investigate the phenomenology of a unified neutrino mixing framework, which serves as the origin of well-known neutrino mixing schemes such as the tribimaximal mixing (TBM), bimaximal mixing (BM), golden ratio mixing (GRM) and hexagonal mixing (HM). Our analysis reveals that the predicted sum of neutrino masses derived from an approximate $μ$-$τ$ reflection symmetric flavor neutrino mass matrix based on the unified neutrino mixing with an inverted mass ordering, is excluded from DESI2024 and Supernova Ia luminosity distance data. This conclusion implies that TBM, BM, GRM, and HM, under an approximate $μ$-$τ$ reflection symmetry with an inverted mass ordering of neutrinos, are also excluded from observations.

hep-ph↗

arXiv2024

Primitive Pythagorean triples and neutrino mixing

The primitive Pythagorean triples are the three natural numbers $(a, b, c)$ that satisfy $c^2=a^2+b^2$ in a right triangle. We constructed a neutrino mixing models related to primitive Pythagorean triples that satisfy the observed values within the $3 σ$ region for the reactor, solar, and atmospheric neutrino mixing angles, as well as the Dirac CP phase.

hep-ph↗

arXiv2024

Constraining scotogenic dark matter and primordial black holes using gravitational waves

The lightest $Z_2$ odd particle in the scotogenic model, referred to as scotogenic dark matter (DM), is a widely studied candidate for DM. This scotogenic DM is generated through well-known thermal processes as well as via the evaporation of primordial black holes (PBHs). Recent reports suggested that the curvature fluctuations of PBHs during an epoch dominated by these entities in the early universe can serve as the source of so-called induced gravitational waves (GWs). In this study, we demonstrate that stringent constraints on the mass of scotogenic DM and PBHs can be obtained through the detection of induced GWs using future detectors.

hep-ph↗

arXiv2023

Composite octet baryons in a relativistic mean field description of nuclear and neutron star matter

We examine the properties of composite octet baryons in the nuclear medium and neutron star matter. The internal quark-diquark structure of the octet baryons and the equations of state of nuclear matter and neutron star matter in the mean field approximation are described by using the three-flavor Nambu--Jona-Lasinio (NJL) model as an effective quark theory of QCD. After introducing our model, we first discuss the properties of single baryons and their effective meson exchange interactions in symmetric nuclear matter by using concepts of Fermi liquid theory. Several model independent implications of this description are derived, and illustrated by numerical results obtained in our model. Second, we extend the model description to high baryon densities, and investigate the equation of state of neutron star matter and the resulting star masses. We find that the so called hyperon puzzle persists also for the case of composite hadrons. To get more information on this point, we also investigate the role of 6-fermi and 8-fermi interactions, in addition to the standard 4-fermi interactions. The strengths of those higher order fermi interactions is determined so as not to spoil the saturation properties of nuclear matter. Among them, an interaction characterized by a product of four quark current operators plays a special role to stabilize the stars over a large region of central baryon densities, although it has little effect on the maximum star masses.

nucl-th↗

arXiv2023

Modified trimaximal mixing for solar and reactor neutrino mixing angles

The trimaximal mixing scheme is one of the widely studied neutrino mixing schemes. However, the predicted solar neutrino mixing angle $θ_{12}$ and the reactor neutrino mixing angle $θ_{13}$ cannot simultaneously realize their best-fit values. To address this issue, a minimal modification to the trimaximal mixing scheme is proposed. The modified trimaximal mixing scheme can simultaneously predict the best-fit values of $θ_{12}$ and $θ_{13}$ using an additional real parameter introduced via the modification.

hep-ph↗

arXiv2023

Neutrino mixing model for best-fit values of $θ_{12}$ and $θ_{13}$

Recently, the precise observations have yielded values for the neutrino mixing angles, denoted as $θ_{12}$ and $θ_{13}$. Therefore, constructing a neutrino mixing model capable of accurately reflecting a these measurements is crucial. In this paper, we propose a novel neutrino mixing model similar to the trimaximal mixing model. Unlike the trimaximal model that falls short of concurrently replicating the best-fit values of $θ_{12}$ and $θ_{13}$, our proposed mixing model has the ability simultaneously reproduce the best-fit values for both angles.

hep-ph↗

arXiv2023

Generalized hybrid natural inflation

Although the hybrid natural inflation is a successful inflation model, the symmetry breaking scale in the model should be large for a negative value of the running of the scalar spectral index. This study proposed a generalized hybrid natural inflation model that can realize a low-scale inflation with a negative value of the running of the scalar spectral index.

hep-ph↗

arXiv2022

Is magic texture for Majorana neutrino immanent in Dirac nature?

The magic textures are successful candidates of the correct texture for the Majorana neutrinos. In this study, we show that some types of magic texture for Majorana neutrinos approximately immanent in the flavor mass matrix for Dirac neutrinos. In addition, it turned out that the normal mass ordering of the Dirac neutrino masses is slightly preferable to the inverted mass ordering in the context of the magic textures.

hep-ph↗

arXiv2022

Primordial black holes and dark matter mass spectrum

Because primordial black holes (PBHs) evaporate into all particle species in nature, PBHs may emit several dark matter (DM) particle species with specific mass spectra. We assume that PBHs are the only source of DMs, and DMs only interact with the standard model particles gravitationally. We show a relation between the number of DM particle species $N_{\rm DM}$ and initial PBH density $β$ and mass $M_{\rm BH}^{\rm in}$. $β$-$M_{\rm BH}^{\rm in}$ curves for different $N_{\rm DM}$ tend to overlap with each other for heavy initial PBHs. We also show that the allowed region of DM masses for multiple DM.

hep-ph↗

arXiv2022

Magic square and three-zero textures for Dirac neutrinos

We show a matrix decomposition of flavor mass matrix for Dirac neutrinos $M$ by sum as $M=M'+M^0$ where $M'$ obeys the feature of the magic square and $M^0$ is three-zero texture. The favorable three-zero textures in the context of magic square are explored. It turned out that so-called the normal ordering of neutrino masses is favored over the inverted ordering in the context of magic square.

hep-ph↗