arXiv subjects

Kento Kamada

Publications and source records attributed to Kento Kamada.

4 recordsLinked to original sources

arXiv2026

First Measurement of the $K^-$ Escape Cross Section in the ${}^{12}{\rm C}(K^{-},p)$ Reaction

We investigated the $\bar{K}$-nucleus interaction through the simultaneous measurement of the inclusive $^{12}{\rm C}(K^-, p)$ and exclusive $K^-$-escape $^{12}{\rm C}(K^-, p K^-_{esc})$ reactions at $1.8$ GeV/$c$ at J-PARC. The present measurement explicitly focuses on the $K^-$ escape process for the first time, successfully accomplishing a direct experimental determination of the imaginary part of the $K^-$ optical potential. The differential cross section for the $K^-$-escape reaction was determined to be $436 \pm 6\:(\text{stat.}) \pm 44\:(\text{syst.})~\mu\text{b/sr}$. A simultaneous likelihood fit yielded real and imaginary potential strengths of $V_0 = -72\:^{+3}_{-5}\:(\text{stat.})\:^{+0}_{-8}\:(\text{syst.})~\text{MeV}$ and $W_0 = -100\:^{+7}_{-1}\:(\text{stat.})\:^{+0}_{-16}\:(\text{syst.})~\text{MeV}$ at the nuclear center, respectively. The derived $W_0$ is significantly stronger than that predicted by theoretical models based on one-nucleon processes, suggesting possible contribution of multi-nucleon involving processes.

nucl-ex↗

arXiv2026

Effective Field Theory for a Baryon-Correlated Dark Matter Profile

While the standard $\Lambda$CDM model succeeds on large cosmological scales, it faces persistent small-scale challenges, including the core-cusp problem, the diversity of galaxy rotation curves, and the tight correlation between dark matter and baryons observed in the Tully-Fisher relation. To address these issues, we recently proposed an empirical law where the effective dark matter energy density is directly correlated with the baryonic gravitational potential, $\rho_{\rm DM} \propto \Phi_b^2$, which reproduces observed rotation curves and resolves the core-cusp and diversity problems. To provide a theoretical foundation for this empirical law, we construct an effective field theory (EFT) introducing massive scalar, vector, and tensor mediators between baryons and a dark sector field $\chi$. We demonstrate that aligning the mediator couplings to a specific ratio (4:6:3) with degenerate masses cancels the additional fifth forces acting on baryons up to $\mathcal{O}(v^2)$. We then show that this theoretical framework originates from a 5-dimensional (5D) spacetime. Treating the baryonic source as a 5D null fluid reveals that the three mediators emerge from a single 5D symmetric tensor field. By confining the field $\chi$ to a 4D brane, we show that its interaction with these mediators generates a pressureless energy density ($\rho_{\rm int} \propto \Phi_b^2$) that yields the empirically required baryon-correlated profile. Consequently, the field $\chi$ exhibits a scale-dependent transition: on cosmological scales, its mass energy acts as standard Cold Dark Matter (CDM), whereas on galactic scales, its interaction energy governs local dynamics. Finally, by evaluating the dynamical boundary of this localized interaction region, we provide a physical interpretation that yields the relation $\mu = K M_b^{-3/2}$, offering a theoretical basis for the Tully-Fisher relation.

astro-ph.CO↗

arXiv2025

Empirical Relationship Between Dark Matter and Baryon Profiles for Solving the Core-Cusp and Diversity Problems of Galaxies

The rotation velocity profiles of galaxies (rotation curves) remain unexpectedly flat at large distances, where visible matter alone should make the rotation velocity decrease with radius. To explain this missing gravity, conventional frameworks assume unseen mass or alternative gravitational effects. While the dark matter hypothesis has become the standard paradigm, this framework faces persistent small-scale challenges, such as the core-cusp and diversity problems, and struggles to explain the observed correlation between dark matter and baryons, as evidenced by the Radial Acceleration Relation and the baryonic Tully-Fisher relation. Here, we introduce a simple empirical law for the dark matter in a single galaxy, stating that the dark matter energy density $\rho_{\mathrm{DM}}$ is related to the baryonic gravitational potential $U_b$ and the total baryonic mass of the galaxy $M_b$ as $\rho_{\mathrm{DM}} = K M_b^{-3/2} (U_b/c^2)^2$. When applied to 122 galaxies from the SPARC database with a single fitting parameter $K$, this empirical equation reproduces both the diverse inner structures and outer flat regions of the observed rotation curves, resolving the core-cusp and diversity problems. In each galaxy, the observed velocity data for various distances were well fitted, with the minimum $\chi^2/\mathrm{dof}$ value around unity, by the rotation curve calculated from this empirical equation. The fitted $K$ values for the 122 galaxies were concentrated within a narrow range, and the minimum $\chi^2/\mathrm{dof}$ values were significantly reduced for galaxies with specific stellar mass-to-light ratio data given by the THINGS survey. These results demonstrate the validity of the empirical law. The success of the empirical law may suggest the existence of new fields interacting with baryons.

astro-ph.GA↗

arXiv2025

Cross section Measurements for $^{12}$C$(K^-, K^+\Xi^-)$ and $^{12}$C$(K^-, K^+\Lambda\Lambda)$ Reactions at 1.8 GeV$/c$

We present a measurement of the production of $\Xi^-$ and $\Lambda\Lambda$ in the $^{12}$C$(K^-, K^+)$ reaction at an incident beam momentum of 1.8 GeV/$\mathit{c}$, based on high-statistics data from J-PARC E42. The cross section for the $^{12}$C$(K^-, K^+\Xi^-)$ reaction, compared to the inclusive $^{12}$C$(K^-, K^+)$ reaction cross section, indicates that the $\Xi^-$ escaping probability peaks at 70\% in the energy region of $E_\Xi=$100 to 150 MeV above the $\Xi^-$ emission threshold. A classical approach using eikonal approximation shows that the total cross sections for $\Xi^-$ inelastic scattering ranges between 42 mb and 23 mb in the $\Xi^-$ momentum range from 0.4 to 0.6 GeV/c. Furthermore, based on the relative cross section for the $^{12}$C$(K^-, K^+\Lambda\Lambda)$ reaction, the total cross section for $\Xi^-p\to\Lambda\Lambda$ is estimated in the same approach to vary between 2.2 mb and 1.0 mb in the momentum range of 0.40 to 0.65 GeV/c. Specifically, a cross section of 1.0 mb in the momentum range of 0.5 to 0.6 GeV/c imposes a constraint on the upper bound of the decay width of the $\Xi^-$ particle in infinite nuclear matter, revealing $\Gamma_\Xi< \sim 0.6$ MeV.

nucl-ex↗