arXiv subjects

Yasuhiro Nakajima

Publications and source records attributed to Yasuhiro Nakajima.

8 recordsLinked to original sources

arXiv2026

Performance evaluation of GYGAG crystals for neutrinoless double beta decay search

Neutrinoless double beta decay (0$\nu\beta\beta$) is a crucial for confirming neutrinos' Majorana characteristics. Previous searches for 0$\nu\beta\beta$ decay of $^{160}$Gd using GSO crystals was conducted, but the sensitivity was limited by background $\alpha$-rays from radioactive impurities. To distinguish the backgrounds, PSD (Pulse Shape Discrimination) and energy resolution are essential. GAGG (Gd$_{3}$(Al, Ga)$_5$O$_{12}$) is a $^{160}$Gd-containing crystal that exhibits a higher light yield than GSO and excellent PSD capabilities. GYGAG (Gd$_{3-x}$Y$_x$(Al, Ga)$_5$O$_{12}$) is a variant crystal where a portion of Gd is substituted with Yttrium and can have enhanced light yield, motivating its investigation for 0$\nu\beta\beta$ decay searches. In this study, GYGAG crystals with different Yttrium concentrations were fabricated and their energy resolution, pulse shape discrimination capability between $\alpha$ and $\gamma$ rays, and scintillation timing characteristics were evaluated for applications in 0$\nu\beta\beta$ decay searches. Y substitution enhanced the light yield, and the best energy resolution was achieved for Gd$_{2.5}$Y$_{0.5}$Al$_2$Ga$_3$O$_{12}$. GYGAG exhibited high pulse shape discrimination performance across various yttrium concentrations.

physics.ins-det↗

arXiv2026

Performance evaluation of Luxium Solutions BCF-XL wavelength-shifting fibers

We evaluate the performance of single-clad wavelength-shifting fibers newly developed by Luxium Solutions, BCF-92XL, BCF-9929AXL, and BCF-9995XL and compare them with the multi-clad Kuraray Y-11 fiber. The BCF-XL fibers exhibit faster decay times (92XL: $2.10\pm0.01$ ns, 9929AXL: $2.10\pm0.02$ ns, 9995XL: $2.41\pm0.03$ ns) than Y-11 ($7.44\pm0.06$ ns). The attenuation lengths are comparable to that of Y-11 within the measurement range up to 3.2 m. When coupled to an EJ-204 plastic scintillator, the BCF-XL fibers achieve superior time resolution while maintaining light yields comparable to those expected for a single-clad Y-11 fiber.

physics.ins-det↗

arXiv2025

In-situ high voltage generation with Cockcroft-Walton multiplier for xenon gas time projection chamber

We have newly developed a Cockcroft-Walton (CW) multiplier that can be used in a gas time projection chamber (TPC). A TPC requires a high voltage to form an electric field that drifts ionization electrons. Supplying the high voltage from outside the pressure vessel requires a dedicated high-voltage feedthrough. An alternative approach is to generate the high voltage inside the pressure vessel with a relatively low voltage introduced from outside. A CW multiplier can convert a low AC voltage input to a high DC voltage output, making it suitable for this purpose. We have integrated a CW multiplier into the AXEL (A Xenon ElectroLuminescence detector), a high pressure xenon gas TPC to search for neutrinoless double beta decay of $^{136}$Xe. It uses silicon photomultipliers to detect the ionization electrons through elecrtoluminescence, making it strong against electronic noise. Operation of the CW multiplier was successfully demonstrated; the TPC was operated for 40 days at 6.8 bar, and an energy resolution as high as (0.67 $\pm$ 0.08) % (FWHM) at 2615 keV was obtained.

physics.ins-det↗

arXiv2024

Performance of new Kuraray wavelength-shifting fibers with short decay time

We measure the decay time and the attenuation length of newly developed wavelength-shifting fibers, YS series from Kuraray, which have fast response. Using a 405 nm laser, the decay times of the YS-2, 4, and 6 are measured to be $3.64 \pm 0.04$ ns, $2.15 \pm 0.03$ ns, and $1.47 \pm 0.02$ ns, respectively, for the light injection distance of 10 cm. The decay time of Y-11 is measured to be $7.10 \pm 0.09$ ns using the same system. All fibers are found to have similar attenuation lengths of more than 4 meters. When combined with the plastic scintillators EJ-200 and EJ-204, the YS series have better time resolution than Y-11, with light yields of 60-100% of Y-11.

physics.ins-det↗

arXiv2023

High-pressure xenon gas time projection chamber with scalable design and its performance at around the Q value of $^{136}$Xe double-beta decay

We have been developing a high-pressure xenon gas time projection chamber (TPC) to search for neutrinoless double beta ($0νββ$) decay of $^{136}$Xe. The unique feature of this TPC is in the detection part of ionization electrons, called ELCC. ELCC is composed of multiple units, and one unit covers 48.5 $\mathrm{cm}^2$. A 180 L size prototype detector with 12 units, 672 channels, of ELCC was constructed and operated with 7.6 bar natural xenon gas to evaluate the performance of the detector at around the Q value of $^{136}$Xe $0νββ$. The obtained FWHM energy resolution is (0.73 $\pm$ 0.11) % at 1836 keV. This corresponds to (0.60 $\pm$ 0.03) % to (0.70 $\pm$ 0.21) % of energy resolution at the Q value of $^{136}Xe$ $0νββ$. This result shows the scalability of the AXEL detector with ELCC while maintaining high energy resolution. Factors determining the energy resolution were quantitatively evaluated and the result indicates further improvement is feasible. Reconstructed track images show distinctive structures at the endpoint of electron tracks, which will be an important feature to distinguish $0νββ$ signals from gamma-ray backgrounds.

physics.ins-det↗

arXiv2010

Search for Muon Neutrino Disappearance in a Short-Baseline Accelerator Neutrino Beam

We report a search for muon neutrino disappearance in the $Δm^{2}$ region of 0.5-40 $eV^2$ using data from both SciBooNE and MiniBooNE experiments. SciBooNE data provides a constraint on the neutrino flux, so that the sensitivity to $ν_μ$ disappearance with both detectors is better than with just MiniBooNE alone. The preliminary sensitivity for a joint $ν_μ$ disappearance search is presented.

hep-ex↗

arXiv2007

Single Pion Measurement Capabilities at SciBooNE

The precise knowledge of the single pion production cross-section of neutrino around the ~1 GeV energy region is an essential ingredient in the interpretation of neutrino oscillation experiments. The unique opportunities and prospects of single pion measurements at SciBooNE are described.

hep-ex↗

arXiv2007

Status of FNAL SciBooNE experiment

SciBooNE is a new experiment at FNAL which will make precision neutrino-nucleus cross section measurements in the one GeV region. These measurements are essential for the future neutrino oscillation experiments. We started data taking in the antineutrino mode on June 8, 2007, and collected 5.19 \times 10^{19} protons on target (POT) before the accelerator shutdown in August. The first data from SciBooNE are reported in this article.

hep-ex↗