arXiv subjects

Tadafumi Kishimoto

Publications and source records attributed to Tadafumi Kishimoto.

7 recordsLinked to original sources

arXiv2026

Nonproportional Response of a GAGG Scintillator to Beta and Gamma Radiation over a Wide Energy Range in PIKACHU

Nonproportional response of scintillation light yield for sub-MeV radiations is a well-known characteristic of inorganic scintillators. In the PIKACHU experiment, a precise understanding of the nonproportional response of the GAGG ($\mathrm{Ce:Gd_3Al_2Ga_3O_{12}}$) scintillator is essential for background modeling. In this study, the nonproportional response of the GAGG scintillator was evaluated for both $β$ and $γ$ rays. The response for $β$ rays was measured using the Compton coincidence technique with a germanium detector, while that for $γ$ rays was evaluated using several monoenergetic $γ$-ray sources. The measurement results showed different responses for $β$ and $γ$ rays, with a stronger nonproportional response for $γ$ rays than for $β$ rays over the energy range of 50--2614~keV. The background model incorporating the measured nonproportional responses reproduced the measured background spectra more accurately compared with the model without the nonproportional response correction. These results demonstrate the importance of precise evaluation of the nonproportional response of the GAGG scintillator which is essential not only for background modeling in the PIKACHU experiment but also for accurate energy calibration in scintillator-based experiments.

physics.ins-det↗

arXiv2026

Breakeven Conditions for Beam-Target Fusion with Electron-Suppressed Targets

This manuscript provides a detailed and extended analysis of the breakeven conditions for nuclear fusion based on beam-target interactions, distinct from conventional plasma-based approaches. Building on the energy-based criterion introduced in the accompanying Letter~\cite{TK_arXiv}, we formulate a self-consistent description of stopping power in electron-suppressed targets and derive quantitative, implementation-agnostic conditions under which fusion energy generation can exceed beam energy loss.

physics.plasm-ph↗

arXiv2026

Breakeven in Nuclear Fusion via Electron-Free Target

Nuclear fusion promises a nearly limitless energy source, but achieving breakeven-where fusion output exceeds input-requires extreme plasma conditions and complex confinement systems. Here we propose an alternative approach based on beam-target interactions, introducing a simple energy-based criterion that compares fusion energy generation with energy loss. By creating electron-free targets, stopping power is drastically reduced, enabling conditions where fusion energy surpasses beam energy deposition under practical scenarios. This approach offers a viable alternative pathway to fusion energy without high-temperature plasma confinement and warrants further experimental investigation.

nucl-ex↗

arXiv2025

Contribution of Subthreshold States to the Residual Energy Distribution of $^{159}$Dy

We investigate the residual energy distribution in the electron capture (EC) process of $^{159}$Dy, emphasizing the role of subthreshold atomic states, which have typically been omitted in conventional spectral analyses. By incorporating these energetically forbidden hole states into the spectral function $P(E)$, we demonstrate a significant enhancement - over an order of magnitude - in the EC rate near the zero-momentum neutrino emission region. This enhancement increases further with larger $Q$ values, contrary to standard expectations. Our analysis shows that $P(E)$ can be experimentally determined, resolving ambiguities near the endpoint and enabling new approaches to 'ultra-low $Q$ value' EC reactions for neutrino mass studies.

nucl-th↗

arXiv2004

Neutrinoless double beta decay and direct searches for neutrino mass

Study of the neutrinoless double beta decay and searches for the manifestation of the neutrino mass in ordinary beta decay are the main sources of information about the absolute neutrino mass scale, and the only practical source of information about the charge conjugation properties of the neutrinos. Thus, these studies have a unique role in the plans for better understanding of the whole fast expanding field of neutrino physics.

hep-ph↗

arXiv2003

$Θ+$: Another Explanation and Prediction

Recently the so-called $Θ^+$ resonance has been reported first from SPring8\cite{nakano} and many following experiments showed apparent confirmation of the state. Since $Θ^+$ exclusively decays into either $K^+ n$ or $K^0 p$, it is explained as the predicted pentaquark state which includes $ u u d d \bar{s}$ quarks. However, one yet has to obtain consistent picture of $Θ^+$ and its quantum numbers. We try to explain $Θ^+$ in a conventional picture and show that such picture leads to new predictions on kaon and pion system.

hep-ex↗

arXiv1999

Kaonic nuclei excited by the $(K^-,N)$ reaction

We show that kaonic nuclei can be produced by the $(K^-,p)$ and $(K^-,n)$ reactions. The reactions are shown to have cross sections experimentally measurable. The observation of the kaonic nuclei gives a kaon-nucleus potential which answers the question on the existence of kaon condensation in dense nuclear matter especially neutron stars.

nucl-th↗