arXiv subjects

Haruto Kitagawa

Publications and source records attributed to Haruto Kitagawa.

4 recordsLinked to original sources

arXiv2026

Uncovering Hidden Leptonic Correlations with Flow Matching and Autoencoders

We perform a global search for values of the Yukawa matrices and Majorana masses in the Type-I seesaw mechanism. Using flow matching, which is a generative artificial intelligence (generative AI) method, we generate a broad set of solutions reproducing the experimentally measured values of the neutrino mass-squared differences and the mixing angles. Then, a machine learning method known as an autoencoder is applied to uncover non-trivial correlations among physical quantities in the lepton sector. Our analysis reveals new non-linear relations involving neutrino masses and CP phases. These findings may contribute to elucidating the origins of the mass hierarchies and mixing patterns among generation structure.

hep-ph↗

arXiv2026

Revisiting One-Zero and Two-Zero Neutrino Mass Textures in Light of Recent Oscillation and Cosmological Data

We revisit one-zero and two-zero textures of the neutrino mass matrix under current experimental and cosmological constraints. We identify the phenomenologically viable texture structures using the latest results on neutrino oscillation parameters, the cosmological bound on the sum of neutrino masses, the kinematic bound on the effective electron-neutrino mass, and limits from neutrinoless double-beta decay. For two-zero textures, several structures are still allowed if only the CMB bound on the neutrino mass sum is imposed. Among them, the $B$-series textures show a characteristic prediction for the Dirac CP phase, with $\delta_{\rm CP}$ lying around $\pi/2$ and $3\pi/2$, and are within the reach of future neutrinoless double-beta decay searches. When the stronger CMB+BAO constraint is included, however, only the $A$-series textures remain viable. Therefore, we also analyze one-zero textures by using machine learning techniques, particularly flow matching. It turns out that some of the texture structures are already excluded by current data, while the allowed ones give distinct predictions for $\sum_i m_i$, $m_{\nu_e}^{\rm eff}$, $\langle m_{ee}\rangle$, and $\delta_{\rm CP}$. We further discuss how the one-zero texture structures can arise from non-invertible selection rules.

hep-ph↗

arXiv2026

Minimal Majoron Dark Matter

We study Majoron dark matter (DM) in its minimal realization, based on the Type-I seesaw framework extended by a SM-singlet complex scalar. Remaining agnostic about the origin and value of the Majoron mass, we evaluate the DM abundance from both the freeze-in and misalignment mechanisms, and identify the viable parameter space consistent with observational constraints. Without fine-tuning of the initial misalignment angle, we find that the Majoron mass is bounded by $m_J \lesssim \mathcal{O}(10)~\mathrm{MeV}$. We also discuss compatibility with thermal leptogenesis. Successful leptogenesis with two right-handed neutrinos favors misalignment-dominated production with the Majoron mass $m_J \lesssim \mathcal{O}(100)~\mathrm{eV}$, while freeze-in dominated production is compatible with leptogenesis only with a mild fine-tuning of the initial misalignment angle, $\theta_i \lesssim \mathcal{O}(0.01)$.

hep-ph↗

arXiv2025

Scaling laws for doublet craters formed by low-velocity impacts of unequal-mass spheres into a granular bed

Understanding the formation mechanism of doublet craters is an important challenge for advancing knowledge in astronomy and granular physics. In this study, we investigated craters formed by low-velocity impacts of two steel spheres with different masses into a granular bed. Even when the masses were different, a figure-eight-shaped doublet crater and a central ridge were observed, similar to the case with equal masses. However, the resulting shape became asymmetric even without a time delay between impacts. The total length of the doublet crater increased depending on the spacing between the two spheres and the ratio of their impact energies. These results followed a theoretical model based on a scaling law, where the crater diameter is proportional to the one-fourth power of the impact energy. A model was also developed to describe the crater overlap, which increases as the spheres become closer. It was also shown that the crater diameters vary with the time difference, and that the second impact tends to form a larger crater due to fluidization induced by the first.

cond-mat.soft↗