arXiv subjects

Katsuhiko Ishida

Publications and source records attributed to Katsuhiko Ishida.

4 recordsLinked to original sources

arXiv2026

Energy spectra of light charged particles emitted following muon nuclear capture on $^\mathrm{nat}$Si

Background: Charged-particle emission following muon nuclear capture (muNC) probes the de-excitation dynamics of highly excited nuclei, particularly the interplay between preequilibrium and evaporation processes. While proton emission has been relatively well studied, data on composite charged particles remain limited, especially for low-energy alpha particles. Purpose: This work aims to measure energy spectra for individual charged-particle species following muNC on silicon and constrain theoretical descriptions of preequilibrium, evaporation, and composite-particle emission. Method: An experiment was performed at the RIKEN-RAL Muon Facility. Charged particles were identified using Delta E-E telescopes and digital pulse-shape analysis with nTD-Si detectors. Initial energy spectra were reconstructed by unfolding and compared with the microscopic and evaporation model (MEM) and PHITS calculations incorporating the surface coalescence model and meson-exchange-current extension. Results: Energy spectra of protons, deuterons, tritons, and alpha particles were extracted over a broad energy range, including the first measurement of the low-energy alpha-particle spectrum. MEM more closely reproduces the proton, deuteron, and triton spectral shapes and describes the low-energy alpha-particle spectrum well. PHITS reproduces the overall slope of the alpha-particle spectrum but exhibits particle-dependent discrepancies in absolute yields, including an overestimation of the evaporation component for all four species. Conclusion: The results demonstrate particle-species-dependent differences in charged-particle emission following muNC. These spectra constrain descriptions of preequilibrium and evaporation processes and highlight the need for improved modeling of composite-particle emission.

nucl-ex↗

arXiv2023

Effect of large-angle incidence on particle identification performance for light-charged ($Z \le 2$) particles by pulse shape analysis with a pad-type nTD silicon detector

In recent years, particle discrimination methods based on digital waveform analysis techniques for neutron-transmutation-doped silicon (nTD-Si) detectors have become widely used for the identification of low-energy charged particles. Although the particle discrimination capability of this method has been well demonstrated for small incident angles, the particle discrimination performance may be affected by changes in the detector response when the detector is moved closer to the charged particle source and the incident position distribution and incident angle distribution to the detector become wide. In this study, we performed a beam test for particle discrimination in light-charged ($Z \le 2$) particles using the digital waveform analysis method with a pad-type nTD-Si detector and investigated the dependence of the performance of the particle discrimination on the incident position and incident angle. As the incident angle increased, a decrease in the maximum current was observed, which was sufficient to affect the performance of the particle discrimination. This decrease can be expressed as a function of the penetration depth of the charged particles into the detector, which varies for each nuclide.

physics.ins-det↗

arXiv2022

Muon-Spin Motion at the Crossover Regime between Gaussian and Lorentzian Distribution of Magnetic Fields

The muon spin relaxation method (μSR) is a powerful microscopic tool to probe electronic states of materials observing local magnetic field distributions on the muon. It often happens that a distribution of local magnetic fields shows intermediate state between Gaussian and Lorentzian shapes. In order to generally describe intermediate field distributions, we dealt the convolution of two isotropic distributions in the three dimension and derived exact muon-spin relaxation functions which can be applied to all crossover regimes between the Gaussian and Lorentzian.

cond-mat.str-el↗

arXiv2017

First FAMU observation of muon transfer from mu-p atoms to higher-Z elements

The FAMU experiment aims to accurately measure the hyperfine splitting of the ground state of the muonic hydrogen atom. A measurement of the transfer rate of muons from hydrogen to heavier gases is necessary for this purpose. In June 2014, within a preliminary experiment, a pressurized gas-target was exposed to the pulsed low-energy muon beam at the RIKEN RAL muon facility (Rutherford Appleton Laboratory, UK). The main goal of the test was the characterization of both the noise induced by the pulsed beam and the X-ray detectors. The apparatus, to some extent rudimental, has served admirably to this task. Technical results have been published that prove the validity of the choices made and pave the way for the next steps. This paper presents the results of physical relevance of measurements of the muon transfer rate to carbon dioxide, oxygen, and argon from non-thermalized excited mu-p atoms. The analysis methodology and the approach to the systematics errors are useful for the subsequent study of the transfer rate as function of the kinetic energy of the mu-p currently under way.

physics.atom-ph↗