arXiv subjects

Jun Miyamoto

Publications and source records attributed to Jun Miyamoto.

3 recordsLinked to original sources

arXiv2026

Heavy Pseudo-Dirac Doublet Dark Matter and Non-Thermal Leptogenesis in Light of the LZ Event

Motivated by the recent LZ candidate nuclear-recoil event, we study pseudo-Dirac electroweak doublet dark matter in the mass range $10^2$--$10^4\,\mathrm{TeV}$, where bounds from searches for neutrinos produced by dark matter annihilation in the Sun can be evaded. To suppress the excessive thermal relic abundance, we consider freeze-out during inflaton domination followed by entropy production during reheating. We examine whether this cosmological history can also accommodate non-thermal leptogenesis. Our analysis includes dark matter production through the emission of virtual electroweak gauge bosons in right-handed-neutrino decays and through thermalization cascades. Our estimates suggest that the two scenarios can be reconciled if dark matter pair emission in right-handed-neutrino decays is kinematically forbidden and cascade production is sufficiently suppressed. Such a realization, however, requires enhanced CP violation, typically involving fine-tuning in the seesaw mechanism or the right-handed-neutrino mass spectrum.

hep-ph↗

arXiv2026

Radiative Breaking of Two-Zero Neutrino Mass Minors: Revisiting the $\mathrm{U}(1)_{L_μ-L_τ}$ Model

The two-zero minor structure predicted by flavor symmetries is usually discussed as a tree-level relation among low-energy neutrino parameters. We point out that this relation can be significantly modified by radiative corrections even when the two-zero minor structure is enforced by an underlying symmetry at tree level. As a concrete example, we analyze the minimal $\mathrm{U}(1)_{L_μ-L_τ}$ model and compute the universal one-loop threshold corrections associated with the type-I seesaw sector. These corrections generate flavor-dependent contributions to the Weinberg operator and violate the exact two-zero minor conditions once the $\mathrm{U}(1)_{L_μ-L_τ}$ symmetry is spontaneously broken. This effect relaxes the tree-level lower bound on the total neutrino mass and thereby weakens the tension between the model and cosmological neutrino-mass constraints.

hep-ph↗

arXiv2026

Complete one-loop QED corrections to $D_s^+$ leptonic decays and impact on the CKM unitarity test

Recently, a violation of the CKM unitarity condition has been reported in the latest charm-meson data and the latest lattice results, once the universal electroweak correction is taken into account. In this article, we analytically derive for the first time the complete one-loop electroweak (EW) and QED corrections to the $D_{s}^+ \to \ell^+ ν_\ell$ decays for $\ell = μ, τ$. Our analysis incorporates both short-distance EW-QED corrections, which are beyond the leading-logarithmic approximation (the so-called Sirlin factor), and long-distance soft-photon corrections depending on the maximum total energy of undetected photons with their resummation. Although the inclusive photon QED corrections to the meson leptonic decays are well known, they do not match the actual measurement circumstances in $D_s^+ \to μ^+ ν_μ$. We find $ |V_{cs}|_{D_s} = 0.991 \pm 0.007 $ from the latest data on $D_s^+$ leptonic decays. We show that properly including these radiative corrections is essential to bring the second-column CKM unitarity tests into agreement with the Standard Model expectation. The study emphasizes that the current limiting factor in confirming CKM unitarity is the precision of QED corrections, and it points out that improving lattice simulations, taking the QED corrections into account, would be desirable for a more robust confirmation.

hep-ph↗