arXiv subjects

Yakefu Reyimuaji

Publications and source records attributed to Yakefu Reyimuaji.

15 recordsLinked to original sources

arXiv2026

Testable neutrino mass and TeV-scale leptogenesis in a $D_4$ inverse seesaw model

An inverse seesaw model for neutrino masses and mixing is proposed, based on the spontaneous breaking of a $D_4$ flavor symmetry. The model simultaneously accounts for the observed neutrino oscillation pattern, the baryon asymmetry of the Universe through TeV-scale leptogenesis, and potentially observable charged-lepton flavor violating (cLFV) processes. A phenomenological analysis shows that the model is consistent with current neutrino oscillation data for both normal and inverted mass orderings. Successful leptogenesis is realized for lightest pseudo-Dirac neutrino masses at the multi-TeV scale. The predicted cLFV branching ratios lie well below the current experimental upper limits while remaining within the sensitivity reach of next-generation experiments. These results establish the model as a viable and testable framework that links low-energy neutrino observables to TeV-scale leptogenesis and cLFV phenomenology.

hep-ph↗

arXiv2026

Neutrino mass and leptogenesis in the non-SUSY modular $A^\prime_5$ inverse seesaw model

A non-supersymmetric inverse seesaw model of neutrino mass based on the $A^{\prime}_5$ modular symmetry is presented. This framework provides a combined explanation for neutrino masses, mixing, and the cosmic baryon asymmetry through leptogenesis. Three concrete realizations are constructed, and their phenomenological predictions are analyzed. The results are not only compatible with the measured neutrino oscillation parameters within the current experimental 3$σ$ ranges, but also provide predictions for the neutrino mass ordering, Dirac and Majorana CP-violating phases, and the effective Majorana mass in neutrinoless double beta decay. The model further realizes TeV-scale leptogenesis consistent with the observed baryon asymmetry, rendering the scenario testable in both low-energy neutrino experiments and high-energy collider searches.

hep-ph↗

arXiv2025

Role of the short-range dynamics in simultaneous interpretation of $P_{cs}$ pentaqurks via $Ξ_c^{(\prime,)}\bar{D}^{()}$ molecules

We investigate hidden-charm molecular states in $Ξ_c^{(\prime,*)}\bar{D}^{(*)}$ systems using the one-boson exchange model. By regulating the short-range interactions with parameter $a$ and cutoff $Λ$, we found ten bound states in isoscalar systems. Our analysis reveals that if the LHCb Collaboration's $P_{cs}(4459)$ and Belle Collaboration's $P_{cs}(4472)$ pentaqurks are indeed distinct states, their mass splitting can be resolved through $Ξ_c^{\prime}\bar{D}$-$Ξ_c\bar{D}^*$ coupled channel dynamics using consistent model parameters. This framework assigns $3/2^-$ and $1/2^-$ spin-parity quantum numbers to $P_{cs}(4459)$ and $P_{cs}(4472)$, respectively. With this consistent model parameter, we predict several new molecular candidates in the $4.3-4.7$ GeV mass region, demonstrating the crucial interplay between coupled channel effects and short-range dynamics in understanding hidden-charm pentaquarks as hadronic molecules. Additionally, we investigate the effects of $Λη_c$ and $ΛJ/ψ$ decay channels on the predicted molecular states, showing how these channels influence pole positions and provide insights into the detectability of these states through different production mechanisms.

hep-ph↗

arXiv2025

Inverse Seesaw Model in Non-holomorphic Modular $A_4$ Flavor Symmetry

This paper investigates an inverse seesaw model of neutrino masses based on non-holomorphic modular $A_4$ symmetry, extending the framework of modular-invariant flavor models beyond the conventional holomorphic paradigm. After the general theoretical framework is established, three concrete model realizations distinguished by their $A_4$ representation assignments and modular weight configurations for the matter fields are analyzed. Focusing on these three specific realizations, a comprehensive analysis of neutrino phenomenology is performed. By constraining the modulus parameter $τ$ to the fundamental domain and systematically scanning the parameter space, regions compatible with current neutrino oscillation data are identified. The numerical results provide predictions for currently unmeasured quantities, including the absolute neutrino mass scale, Dirac CP-violating phase, and Majorana phases. These predictions establish specific, testable signatures for upcoming neutrino experiments, particularly in neutrinoless double beta decay and precision oscillation measurements. The framework offers a well-defined target for future experimental verification or exclusion, while demonstrating the phenomenological viability of non-holomorphic modular symmetry approaches to flavor structure.

hep-ph↗

arXiv2025

A $Z_4$ symmetric inverse seesaw model for neutrino masses and FIMP dark matter

A theoretical framework based on a spontaneously broken $Z_4$ symmetry is proposed to simultaneously explain neutrino mass generation via the inverse seesaw mechanism and dark matter (DM) production through a freeze-in scenario. This work extends the standard model with right-handed neutrinos $N_i$, additional fermions $χ_i$, and a complex scalar $S$. An unbroken $Z_2$ subgroup ensures the stability of the DM candidate, whose relic abundance is dominantly produced via decay and scattering processes involving heavy singlet fermions. Phenomenological analyses show that this relatively minimal construction accommodates the observed neutrino oscillation parameters, consistent with the latest global fit data. Furthermore, the model successfully reproduces the observed DM relic density within the parameter space relevant to neutrino phenomenology, establishing a connection between neutrino properties and DM production.

hep-ph↗

arXiv2025

Dirac Neutrinos and Dark Matter within a Minimal Discrete Symmetry Model

We present a model that extends the standard model by incorporating the simplest discrete symmetry groups, $Z_2$ and $Z_3$. This model introduces vector-like leptons and a real scalar singlet. Based on this framework, we generate Dirac neutrino masses and explain the neutrino normal mass ordering. The model also aligns well with current oscillation data regarding theoretical values of the leptonic mixing angles and the Dirac CP-violating phase. Furthermore, it predicts that the atmospheric mixing angle falls in the higher octant and proposes a viable dark matter candidate. We also discuss other phenomenological aspects and future testability of the model.

hep-ph↗

arXiv2025

Aharonov-Bohm Effects for Electromagnetism and Gravity in Four-Dimensional Spacetime

This paper investigates a geometric framework for the gravitational Aharonov-Bohm effect in four-dimensional spacetime, demonstrating how spacetime curvature induces nonlocal quantum phase shifts within field-free regions. By constructing vector bundles on spacetime manifolds equipped with Levi-Civita connections, we derive the holonomy transformations for parallel-transported quantum states. Under the Newtonian approximation, metric decomposition into Minkowski background plus scalar potential perturbations reveals through the linearized Einstein field equations that the gravitationally induced phase shift is mathematically isomorphic to its electromagnetic counterpart. These results establish the quantum observability of gravitational gauge structures and provide theoretical support for experimental verification via atom interferometry.

gr-qc↗

arXiv2024

Constraining light dark matter and mediator with $B^+ \rightarrow K^+ ν\bar ν$ data

We study the decay of $B^+$ meson into $K^+$ plus a light mediator $ϕ$, which subsequently decays into a dark matter pair, $\bar χχ$. Integrating constraints from DM relic density, direct detection, collider data and $B$-physics, alongside the recently reported results form Belle II experiment, we analyze the couplings between the mediator, standard model fermions, and the dark matter particles. Our results indicate that if the decay process $ϕ\rightarrow \bar χχ$ is kinematically allowed, i.e. $m_ϕ> 2m_χ$, then the mediator mass must be constrained within 0.35 GeV $\lesssim m_ϕ\lesssim$ 3 GeV. Conversely, if $m_ϕ< 2m_χ$, the mediator $m_ϕ$ is long-lived relative to the detector size, and the only allowed decay channel is $ϕ\rightarrow e^+ e^-$.

hep-ph↗

arXiv2022

Slow-roll inflation in $f(R,T)$ gravity with a $RT$ mixing term

We consider slow-roll inflationary models in a class of modified theories of gravity which contains non-minimal curvature-inflaton couplings, i.e., the $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the inflaton energy-momentum tensor. On top of the minimally coupled $T$ that has been widely investigated in the literature, we further include a $RT$ mixing term in the theory. This mixing term introduces non-minimal derivative couplings and plays an important role in inflationary dynamics. Taking chaotic and natural inflation as examples, we find that the predictions for spectral tilt and the tensor-to-scalar ratio are sensitive to the existence of the $RT$ mixing term. In particular, by turning on this mixing term, it is possible to bring chaotic and natural inflation into better agreement with observational data.

gr-qc↗

arXiv2022

Axionic Dirac seesaw and electroweak vacuum stability

We explore the connection between tree-level Dirac neutrino masses and axion physics in a scenario where the PQ symmetry enforces lepton number conservation perturbatively. Requiring that the PQ scale $f_a$ is the only heavy scale to play a role in neutrino mass generation, we are led to the construction of a KSVZ-type model where Dirac neutrino masses are inversely proportional to $f_a$, provided a real scalar triplet (zero hypercharge) is added to the SM scalar sector. We analyse this extended scalar sector, focusing on the stabilisation of the electroweak vacuum. The contribution of the triplet VEV to the $W$ mass may also be responsible for the recent hint of beyond-the-SM physics by the CDF collaboration.

hep-ph↗

arXiv2022

Modified gravity models for inflation: In conformity with observations

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct $f(ϕ)T$ term, where $ϕ$ is identified as the inflaton and $T$ is the trace of the energy-momentum tensor. The framework goes to Einstein gravity naturally when the inflaton decays out. We investigate inflation dynamics in this $f(ϕ)T$ gravity (not to be confused with torsion-scalar coupled theories) on a general basis and then apply it to three well-motivated inflationary models. We find that the predictions for the spectral tilt and the tensor-to-scalar ratio are sensitive to this new $f(ϕ)T$ term. This $f(ϕ)T$ gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.

gr-qc↗

arXiv2021

A chiral model for sterile neutrino

A model, which extends the standard model with a new chiral U(1)$'$ gauge symmetry sector, for the eV-mass sterile neutrino is constructed. It is basically fixed by anomaly free conditions. The lightness of the sterile neutrino has a natural explanation. As a by product, this model provides a WIMP-like dark matter candidate.

hep-ph↗

arXiv2021

Warm-assisted natural inflation

We consider natural inflation in a warm inflation framework with a temperature-dependent dissipative coefficient $Γ\propto T^3$. Natural inflation can be compatible with the Planck 2018 results with such warm assistance. With no a priori assumptions on the dissipative effect's magnitude, we find that the Planck results prefer a weak dissipative regime for our benchmark scale $f=5 M_{\rm pl}$, which lies outside the $2σ$ region in the cold case. The inflation starts in the cold regime and evolves with a growing thermal fluctuation that dominates over quantum fluctuation before the end of the inflation. The observed spectral tilt puts stringent constraints on the model's parameter space. We find that $f< 1 M_{\rm pl}$ is excluded. A possible origin of such dissipative coefficient from axion-like coupling to gauge fields and tests of the model are also discussed.

astro-ph.CO↗

arXiv2021

Natural inflation with a nonminimal coupling to gravity

Although natural inflation is a theoretically well-motivated model for cosmic inflation, it is in tension with recent Planck cosmic microwave background anisotropy measurements. We present a way to alleviate this tension by considering a very weak nonminimal coupling of the inflaton field to gravity in both contexts of metric and Palatini formulations of general relativity. We start our discussions with a generic form of the inflaton coupling to the Ricci scalar, then focus on a simple form to do phenomenological study. Our results show that such an extension can bring natural inflation's predictions to a good agreement with the Planck data. Depending on values of the coupling constant $ξ$ and the symmetry breaking scale $f$, we find that with $|ξ|\sim 10^{-3}$ and $f\gtrsim 2.0 M_{\mathrm{pl}}$ predictions of the model stay inside $68\%$ CL allowed region until $f$ increases up to $7.7 M_{\mathrm{pl}}$, then only inside $95\%$ CL region after $f$ exceeds the latter value. The predictions from the metric and the Palatini theories are very similar due to the simple form of the coupling function we use and the small magnitude of the coupling $ξ$. Successful reheating can also be realized in this model.

astro-ph.CO↗

arXiv2020

Prospects of light sterile neutrino searches in long-baseline neutrino oscillations

The neutrino oscillation probabilities in vacuum and matter are discussed, considering the framework of three active and one light sterile neutrinos. We study in detail the rephasing invariants and CP asymmetry observables, and investigate the four-neutrino oscillations in long-baseline neutrino experiments, such as DUNE, NO$ν$A and T2HK. Our results show that the matter effect enhances quite a significantly the oscillation probabilities of electron neutrino and electron antineutrino appearance channels within a certain energy range, while no considerable change arises in the CP asymmetry analysis due to the matter effect. Moreover, separation between the results with and without the sterile neutrino is not so significant and that is also affected by CP-violating phases. Comparing the results for these three experiments, all of them have similar features, nevertheless, sizes and separations of the oscillation probabilities in DUNE are bit larger.

hep-ph↗