arXiv subjects

Naoyuki Haba

Publications and source records attributed to Naoyuki Haba.

At least 19 recordsLinked to original sources

arXiv2026

Correlation Between Proton Decay Channels and the Axion Mass in an Extended SU(5) GUT

We study a renormalizable SU(5) grand unified theory (GUT) supplemented by a 45-dimensional Higgs field and a DFSZ axion sector, imposing a Georgi--Jarlskog flavor structure at the unification scale. We perform a one-loop gauge coupling unification analysis, explicitly including the threshold masses of the light multiplets arising from the 45-dimensional Higgs field. This analysis identifies the viable region in the $(M_{\mathrm{GUT}},M_{S_1})$ parameter space. Through the relation between the unification and PQ scales, this region yields correlated predictions for the QCD axion mass. The Georgi--Jarlskog assumption substantially reduces the flavor ambiguity of the dimension-six baryon-violating operators, enabling robust constraints and predictions not only for antineutrino modes but also for charged-lepton proton decay modes such as $p \to e^+ \pi^0$. We present the combined implications for proton decay and axion searches, showing how the GUT-selected parameter region maps onto the axion mass, the axion-photon coupling, and the axion-induced EDM coupling.

hep-ph↗

arXiv2026

Optimizing Yukawa couplings to suppress Dimension-five Proton Decay in $SU(5)$ GUT

The minimal supersymmetric $SU(5)$ grand unified theory (GUT) provides a highly compelling framework for physics beyond the Standard Model (SM). However, it suffers from a severe phenomenological challenge: rapid proton decay mediated by colored-Higgsino exchange via dimension-five operators. Resolving this issue often requires adjustments to the Yukawa couplings and the potential sectors, generating a vast and complex parameter space where traditional brute-force numerical scans are rendered computationally intractable due to the curse of dimensionality. In this paper, we overcome this limitation by applying machine learning optimization techniques. We investigate a supersymmetric $SU(5)$ model extended with $\mathbf{45}$ and $\overline{\mathbf{45}}$ Higgs representations, defining a loss function based on the partial decay width of $p \to K^+ \bar{\nu}$. Utilizing the Adam optimizer, we systematically explore the 33-dimensional parameter space to identify regions that suppress proton decay. Furthermore, we vary $\tan \beta$ to thoroughly investigate whether the optimized proton lifetime can consistently exceed the stringent experimental lower bound of $5.9 \times 10^{33}$ years established by the Super-Kamiokande collaboration.

hep-ph↗

arXiv2025

Gravitational Waves from Phase Transition in a Supersymmetric Left-Right Model

We investigate the cosmological phase transition dynamics in a supersymmetric left-right symmetric model based on the gauge group $SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ that addresses the strong CP problem through extended parity symmetry and doublet-doublet splitting. We compute the finite temperature effective potential including one-loop Coleman-Weinberg corrections, thermal contributions, and daisy resummation to determine whether the $SU(2)_R \times U(1)_{B-L} \to U(1)_Y$ symmetry breaking transition can produce observable gravitational waves. For phenomenologically viable parameters satisfying current LHC constraints, we find that the phase transition is strongly first-order with nucleation temperature $T_n \sim 0.5 v_R$, transition strength parameter $\alpha \sim 0.01-0.3$, and inverse duration $\beta/H \sim 100$. The resulting stochastic gravitational wave background peaks at frequencies $f \sim 0.1-1$ Hz with amplitude $h^2\Omega_{GW} \sim 10^{-14}-10^{-12}$. We find that there is a parameter region where the gravitational wave spectrum overlaps with DECIGO/BBO sensitivity curves, providing a potentially observable signature connecting the theoretical solution to the strong CP problem with gravitational wave experiments.

hep-ph↗

arXiv2024

Non-thermal baryogenesis from MSSM flat direction

We study an inflection point inflation scenario where a flat direction of the minimal supersymmetric standard model (MSSM) is identified with the inflaton. We focus on the case where the flat direction (inflaton) has non-zero baryon number, and consider a non-thermal baryogenesis scenario where the decay of the inflaton at the reheating directly generates baryon asymmetry of the Universe. Specifically, we consider a udd flat direction that is lifted by a superpotential operator of dimension 6, and show that inflection point inflation with the udd flat direction can be compatible with cosmological observations and can account for the baryon asymmetry of the Universe.

hep-ph↗

arXiv2024

Indirect Detection for Higgs Portal Majorana Fermionic Dark Matter

We study the $\gamma$-ray signal emitted from dark matter (DM) pair annihilation in the Higgs portal Majorana fermion DM model. In the model, a Majorana fermion DM $\chi$ couples with the Standard Model (SM) Higgs field $H$ through a higher-dimensional term $-{\cal L}\supset H^\dagger H \bar{\chi}\chi/\Lambda$, where $\Lambda$ is a cutoff scale. The pair annihilation of $\chi$ through the above term produces the Higgs boson and the longitudinal modes of $W,Z$ gauge bosons. The Milky Way dwarf spheroidal satellite galaxies (dSphs) are used as the most promising targets to search for the $\gamma$-ray signal of the model, due to high DM density and lack of astrophysical backgrounds. The {\it Fermi} Large Area Telescope ({\it Fermi}-LAT) is used for the search, for its high sensitivity. In this work, we use 14-year {\it Fermi}-LAT data from 16 dSphs, to constrain the DM pair annihilation cross section for the DM mass range from 125 GeV to 100 TeV.

hep-ph↗

arXiv2024

Proton Decay and Gauge Coupling Unification in an Extended SU(5) GUT with 45-Dimensional Higgs

We present a comprehensive study of an extended SU(5) grand unified theory (GUT) that incorporates a 45-dimensional Higgs representation to address the shortcomings of the minimal SU(5) GUT, such as the inability to generate realistic fermion mass hierarchies and insufficient proton stability. By considering a hierarchical mass spectrum for the scalar components of the 45-Higgs, we demonstrate that successful gauge coupling unification (GCU) can be achieved. The color octet scalar, color triplet scalar, and color anti-triplet scalar play crucial roles in realizing GCU when their masses are significantly lighter than other components of the 45-Higgs. We focuses on the proton decay channels mediated by the exchange of the color anti-triplet scalar. Assuming that the 45-Higgs couples to all three generations of fermions, we determine the 45-Higgs Yukawa couplings with which the observed fermion mass matrices at low energies are realized. We calculate proton decay rates using the Yukawa couplings obtained from renormalization group evolutions and matching conditions at the GUT scale, thereby exploring the dependence of proton decay rates on model parameters. We find that the $p \to \nu \pi$ mode imposes the most stringent constraint on the mass of the color anti-triplet scalar $M_{S_1}$. We also study the correlations between the lower bounds on $M_{S_1}$ derived from different proton decay modes.

hep-ph↗

arXiv2024

Confronting MSSM flat direction inflation with Planck/BICEP data

We study the scenario of inflection point inflation where a flat direction of the minimal supersymmetric standard model (MSSM) is identified with the inflaton. Specifically, we consider in full generality the cases where a MSSM flat direction is lifted by a higher-dimensional superpotential whose dimension is n = 4, 5, 6, 7, 9. We confront the inflection point inflation scenarios with various n with the Planck and BICEP data, and thereby constrain the soft SUSY breaking mass and the coefficient of the higher-dimensional operator that lifts the flat direction.

hep-ph↗

arXiv2024

Gauge coupling unification and proton decay via 45 Higgs boson in SU(5) GUT

We study the gauge coupling unification (GCU) and proton decay in a non-supersymmetric SU(5) grand unified theory (GUT) incorporating a 45 representation Higgs field. Our analysis is based on the assumption that Georgi-Jarlskog-type mass matrices for fermions are responsible for explaining the mass ratio of the strange quark and the muon. We examine the conditions of GCU, taking into account the possibility that certain components of the 45 Higgs field have masses much smaller than the GUT scale. We have found that to satisfy the GCU conditions, at least two components of the 45 Higgs field should have such small masses. We search the parameter space to identify regions where the GCU conditions are satisfied, in the scenarios where two or three components of the 45 Higgs boson are hierarchically light. If the colored Higgs component of the 45 Higgs boson has a mass much smaller than the GUT scale, proton decay via colored Higgs boson exchange can occur with an observably large rate. We estimate the mass bounds for the colored Higgs component from the proton decay search at Super- Kamiokande and thereby further restrict the parameter space.

hep-ph↗

arXiv2023

Higgs Portal Majorana Fermionic Dark Matter with the Freeze-in Mechanism

We consider a minimal model of fermionic dark matter, in which the Majorana fermion dark matter (DM) $χ$ couples with the Standard Model (SM) Higgs field $H$ through a higher-dimensional term $-{\cal L}\supset H^\dagger H \barχχ/Λ$, where $Λ$ is the cutoff scale. We assume that $Λ$ is sufficiently large that DM particles are not in thermal equilibrium with the SM Particles throughout the history of the Universe. Hence, DM particles are produced only by the freeze-in mechanism. Through a numerical analysis of the freeze-in mechanism, we show contour plots of the DM relic abundance for various values of the DM mass, reheating temperature and the cutoff scale. We obtain an upper bound of the DM mass and cutoff scale from contour plots on ($m_χ, Λ$)-plane. We also consider the direct DM detection for the parameter regions where the DM relic abundance is consistent with the experimental values. We find that the spin-independent cross section for the elastic scattering with a nucleon is below the current experimental upper bound.

hep-ph↗

arXiv2023

Vacuum stability and Q-ball formation in the Type II Seesaw model

We investigate vacuum stability and Q-ball formation in the Type II seesaw model by considering the effective potential for scalar fields, taking into account renormalization effects. We find that the quartic coupling for the triplet Higgs can vanish at a high energy scale, creating a flat direction where Q-ball formation can occur. If Q-balls are produced, they eventually decay into leptons via neutrino Yukawa couplings with the triplet Higgs. If this decay occurs above the electroweak scale, the leptogenesis scenario can work, and the baryon number is produced via the sphaleron effect. We show that there are parameter regions where the above scenario occurs, taking into account phenomenological constraints.

hep-ph↗

arXiv2023

Neutrino Mass in Non-Supersymmetric $SO(10)$ GUT

We study a prediction on neutrino observables in a non-supersymmetric renormalizable $SO(10)$ GUT model that contains a ${\bf 10}$ complex scalar field and a ${\bf 126}$ scalar field whose Yukawa couplings with ${\bf 16}$ matter fields provide the quark and charged lepton Yukawa couplings, neutrino Dirac Yukawa coupling and Majorana mass for the singlet neutrinos. The $SO(10)$ breaking is achieved in two steps by a ${\cal O}(10^{15})$ GeV VEV of a ${\bf 54}$ real scalar field and a ${\cal O}(10^{14})$ GeV VEV of the ${\bf 126}$ field. First, we analyze the gauge coupling unification conditions and determine the VEV of the ${\bf 126}$ field. Next, we constrain the Yukawa couplings of the ${\bf 10}$ and ${\bf 126}$ fields at the scale of the ${\bf 126}$ field's VEV from experimental data on quark and charged lepton masses and quark flavor mixings. Then we express the active neutrino mass with the above Yukawa couplings and the ${\bf 126}$ field's VEV based on the Type-1 seesaw mechanism, and fit neutrino oscillation data, thereby deriving a prediction on poorly or not measured neutrino observables. What distinguishes our work from previous studies is that we do not assign Peccei-Quinn charges on visible sector fields so that the ${\bf 10}$ scalar field and its complex conjugate both have Yukawa couplings with ${\bf 16}$ matter fields. From the fitting of neutrino oscillation data, we find that not only the normal neutrino mass hierarchy, but also the inverted hierarchy can be realized. We also reveal that in the normal hierarchy case, the Dirac CP phase of the neutrino mixing matrix $δ_{CP}$ is likely in the ranges of $-2.4<δ_{\rm CP}<-1.2$ and $1.2<δ_{\rm CP}<2.4$, and not in the region with $δ_{\rm CP}\simπ$, and that in the normal hierarchy case, $θ_{23}$ is likely in the upper octant and in the range of $0.50\lesssim\sin^2θ_{23}\lesssim0.55$.

hep-ph↗

arXiv2023

Conditions for Suppressing Dimension-five Proton Decay in Renormalizable SUSY $SO(10)$ GUT

The SUSY $SO(10)$ GUT is in severe tension with the experimental bounds on proton partial lifetimes because proton decay mediated by colored Higgsinos (dimension-five proton decay) is too rapid. In this paper, we pursue the possibility that a texture of the Yukawa coupling matrices in a renormalizable SUSY $SO(10)$ GUT model suppresses dimension-five proton decay. We focus on a general renormalizable SUSY $SO(10)$ GUT model which contains ${\bf 10}+{\bf 126}+{\bf \overline{126}}+{\bf 120}$ representation fields and where the Yukawa coupling matrices of the ${\bf 16}$ matter fields with the ${\bf 10}$, ${\bf \overline{126}}$, ${\bf 120}$ fields, $Y_{10},Y_{126},Y_{120}$, provide the quark and lepton Yukawa couplings and Majorana mass of the singlet neutrinos. We find that if components in certain flavor bases, $(Y_{10})_{u_R d_R}$, $(Y_{126})_{u_R d_R}$, $(Y_{10})_{u_R s_R}$, $(Y_{126})_{u_R s_R}$, $(Y_{10})_{u_L d_L}$, $(Y_{126})_{u_L d_L}$, $(Y_{10})_{u_L s_L}$, $(Y_{126})_{u_L s_L}$, $(Y_{10})_{u_L u_L}$, $(Y_{126})_{u_L u_L}$, are all on the order of the up quark Yukawa coupling, dimension-five proton decay can be suppressed while the Yukawa coupling matrices still reproduce the realistic quark and lepton masses and flavor mixings. We numerically obtain specific Yukawa coupling matrices satisfying the above conditions, calculate proton partial lifetimes from them and evaluate how dimension-five proton decay is suppressed when these conditions are met.

hep-ph↗

arXiv2023

Neutrino mass square ratio and neutrinoless double beta decay in random neutrino mass matrices

We study the neutrino mass anarchy in the Dirac neutrino, seesaw, double seesaw models. Assuming the anarchy hypothesis, the mass matrices are random and distributed in accordance with the Gaussian measure. We focus on the distributions of mass square ratio of the light neutrinos and examine which of these models shows a peak in the probability distribution around the experimental value. We show that the peak position depends on the number of random matrix products. We find that the light neutrino mass hierarchy becomes larger as the number of random matrix products is increased and the seesaw model with the random Dirac and Majorana mass matrices is the most probable to realize the current experimental data. We also investigate the distributions of the effective Majorana mass for neutrinoless double beta decay. We find that the effective Majorana mass is smaller than the experimental upper bound and tends to be smaller as the number of random matrix products increases because the light neutrino masses become more hierarchical. We argue that the tendency for lighter neutrino masses to become more hierarchical as the number of products in the random matrix increases can be understood from the probability distribution of singular values in random matrix theory.

hep-ph↗

arXiv2022

Revisiting Quantum Stabilization of the Radion in Randall-Sundrum Model

We study the stabilization of the radion in Randall-Sundrum-1 model by the Casimir energy of a bulk gauge field. The Casimir energy is proportional to a divergent, infinite summation over the zeros of a Wronskian of Bessel functions that implicitly depends on the radion vacuum expectation value, and its regularization and renormalization is the central issue. We carry out the correct regularization and renormalization by noting that analytic continuation must be performed only on functions that are independent of the radion vacuum expectation value. Thereby we find that the 1-loop effective potential of the radion generated by the Casimir energy can be renormalized with the boundary tensions, and we correctly obtain the renormalized effective potential. It is shown that a bulk gauge field satisfying Dirichlet condition at the positive (UV) boundary and Dirichlet condition at the negative (IR) boundary gives rise to an appropriate radion potential that stabilizes the radion vacuum expectation value in a way that a large hierarchy of the warp factor is generated naturally.

hep-ph↗

arXiv2022

Moderately Suppressed Dimension-five Proton Decay in a Flipped $SU(5)$ Model

We study colored Higgsino-mediated proton decay (dimension-five proton decay) in a model based on the flipped $SU(5)$ GUT. In the model, the GUT-breaking ${\bf10}$, ${\bf \overline{10}}$ fields have a GUT-scale mass term and gain VEVs through higher-dimensional operators, which induces an effective mass term between the color triplets in the ${\bf 5}$, ${\bf \bar{5}}$ Higgs fields that is not much smaller than the GUT scale. This model structure gives rise to observable dimension-five proton decay, and at the same time achieves moderate suppression on dimension-five proton decay that softens the tension with the current bound on $Γ(p\to K^+ν)$. We investigate the flavor dependence of the Wilson coefficients of the operators relevant to dimension-five proton decay, by relating them with diagonalized Yukawa couplings and CKM matrix components in MSSM, utilizing the fact that the GUT Yukawa couplings are in one-to-one correspondence with the MSSM Yukawa couplings in flipped models. Then we numerically evaluate the Wilson coefficients, and predict the distributions of the ratios of the partial widths of various proton decay modes.

hep-ph↗

arXiv2022

Are Low-energy Data already Hinting at Five Dimensions?

Low-energy data, combined with renormalization group (RG) equations, can predict new physics at far higher energy scales. In this paper, we consider the possibility that the measured Higgs boson mass and top quark mass hint at a five-dimensional gauge-Higgs unification (5D GHU) model at a scale above TeV. We note that the vanishing of the Higgs quartic coupling and the proximity of the top quark Yukawa coupling and weak gauge coupling at high scales, inferred from the experimental data, are in harmony with 5D GHU, because in 5D GHU models the Higgs quartic coupling is forbidden by the 5D gauge symmetry and the Yukawa couplings and the weak gauge coupling originate from a common 5D gauge coupling. Based on the above insight, we propose a 5D GHU model where the Standard Model fermions are embedded in 5D fermions in a way to tightly relate the top Yukawa coupling with the weak gauge coupling. Also, the model predicts the presence of vector-like fermions (other than the Kaluza-Klein modes), which can affect the RG evolutions of the 4D theory and reconcile the scale of vanishing Higgs quartic coupling and that of equality of the top Yukawa and weak gauge couplings, thereby achieving a successful matching of the 4D theory with 5D GHU. We predict the vector-like fermion mass and the compactification scale of 5D GHU from the conditions for the successful matching.

hep-ph↗

arXiv2020

Renormalizable $SO(10)$ GUT with Suppressed Dimension-5 Proton Decays

We study a renormalizable SUSY $SO(10)$ GUT model where the Yukawa couplings of single ${\bf 10}$, single ${\bf \overline{126}}$ and single ${\bf 120}$ fields, $Y_{10},Y_{126},Y_{120}$, account for the quark and lepton Yukawa couplings and the neutrino mass. We pursue the possibility that $Y_{10},Y_{126},Y_{120}$ reproduce the correct quark and lepton masses, CKM and PMNS matrices and neutrino mass differences, and at the same time suppress dimension-5 proton decays (proton decays via colored Higgsino exchange) through their texture, so that the soft SUSY breaking scale can be reduced as much as possible without conflicting the current experimental bound on proton decays. We perform a numerical search for such a texture, and investigate implications of that texture on unknown neutrino parameters, the Dirac CP phase of PMNS matrix, the lightest neutrino mass and the $(1,1)$-component of the neutrino mass matrix in the charged lepton basis. Here we concentrate on the case when the active neutrino mass is generated mostly by the Type-2 seesaw mechanism, in which case the correlation between the suppression of dimension-5 proton decays and the neutrino parameters is expected to be most direct.

hep-ph↗

arXiv2020

Charged Lepton Flavor Violating processes in Neutrinophilic Higgs+Seesaw model

We investigate charged lepton flavor violating (CFLV) processes in the `neutrinophilic Higgs+seesaw model', in which right-handed neutrinos couple only with an extra Higgs field which develops a tiny VEV and the right-handed neutrinos also have Majorana mass. The model realizes a seesaw mechanism around TeV scale without extremely small Dirac Yukawa couplings. A phenomenological feature of the model is CFLV processes induced by loop diagrams of the charged scalar particles and heavy neutrinos. Therefore, first we constrain the model's parameter space from the search for $μ\to eγ$. Next, we predict the branching ratios of other CFLV processes including the $μ\to3e$, $μ+{\rm Al}\to e+{\rm Al}$, $μ+{\rm Ti}\to e+{\rm Ti}$, $Z\to eμ$, $Z\to eτ$, $Z\to μτ$, $h\to eτ$, $h\toμτ$ processes, and discuss their detectability in future experiments.

hep-ph↗