Searcharxiv⌕ Search

arXiv subjects

Y. Yamaguchi

Publications and source records attributed to Y. Yamaguchi.

At least 19 recordsLinked to original sources
arXiv2026

Deposition of $α$ clusters on the surface of $^{28}$Si

The possibility of the appearance of the clustering structure in the surface is one of the key features determining the nuclear structural properties. In this work, we study the ground-state structure of $^{28}\text{Si}$ using the antisymmetrized quasicluster model (AQCM), focusing on the deposition of the $α$ cluster structure on the surface. Three candidate structural configurations constrained to reproduce the experimental charge radius are investigated based on the $\text{SU}(3)$ shell model, the $j$-$j$ coupling shell model, and a localized $7α$ cluster model. Using Glauber-model calculations for intermediate-energy proton elastic scattering, we demonstrate that the angular distribution at and beyond the first diffraction peak is highly sensitive to surface diffuseness, and that the $7α$ cluster model configuration best reproduces the experimental data due to its sharper surface profile. Also, the elastic charge form factors from electron scattering support the existence of the cluster-induced oblately deformed structure.

nucl-th↗
arXiv2026

The Intermediate Silicon Tracker Detector for sPHENIX

A new barrel-type silicon detector has been constructed in the central rapidity region of the sPHENIX experiment as part of its charged-particle tracking system. The detector, referred to as the intermediate silicon tracker (INTT), provides single-event timing capability and contributes to charged-particle tracking in combination with the silicon-pixel vertex detector and the time-projection chamber. The INTT consists of two cylindrical barrels with full azimuthal coverage. The inner and outer barrels comprise 24 and 32 silicon strip ladders, respectively. Each ladder consists of four silicon strip sensors, covering the pseudorapidity range $|η| < 1.07$ for collision vertices within $\pm~10$ cm along the beam axis, at radial distances between 72 and 103 mm. The INTT has been fully integrated into the sPHENIX data acquisition system, with detector signals processed by eight FELIX servers. Continuous data taking is enabled by a streaming readout mode, in which detector data are accumulated without hardware triggers, while a conventional trigger-based mode is also supported. The detector achieves stable operation, small inactive area, and high efficiency, providing precise timing, tracking, and vertexing performance during the collection of beam-beam collision data.

physics.ins-det↗
arXiv2026

First Extraction of the Matter Radius of $^{132}$Sn via Proton Elastic Scattering at 200 MeV/Nucleon

The angular distribution of the differential cross sections for proton elastic scattering from $^{132}$Sn at 196-210 MeV/nucleon was successfully measured over a momentum transfer range of 0.80 to 2.1 fm$^{-1}$. Using a relativistic impulse approximation, the root-mean-square matter radius of $^{132}$Sn was extracted to be $4.758^{+0.023}_{-0.024}$ fm, which was compared with the state-of-the-art ab initio calculations. Combined with the charge radius measured at ISOLDE, there are no theoretical calculations consistent with both matter and charge radii within the experimental errors.

nucl-ex↗
arXiv2026

First results from the search for an excess of $\barν_{e}$ events in JSNS$^2$

The JSNS$^2$ (J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source) experiment at the Material and Life Science Facility (MLF) of J-PARC is designed to directly test an excess on $\barν_{e}$ events which was indicated by LSND (Liquid Scintillator Neutrino Detector). The combination of a short-pulsed proton beam and a gadolinium-loaded liquid scintillator provides an excellent signal-to-noise ratio. In this article, we report the first results of a direct test based on data collected in 2022. After applying all event selection criteria, two events are observed, consistent with the expected background of 2.3$\pm$0.4 events. No excess of $\barν_e$ events are seen in this report, however the expected number of events due to LSND anomaly is 1.1$\pm$0.5, thus this result is not yet conclusive. Data taking has been ongoing since 2021 and will continue in future runs. In addition, a new far detector has recently been constructed for the second phase experiment, JSNS$^2$-II, marking an important milestone toward forthcoming measurements.

hep-ex↗
arXiv2025

Muon tagging with Flash ADC waveform baselines

This manuscript describes an innovative method to tag the muons using the baseline information of the Flash ADC (FADC) waveform of PMTs in the JSNS1 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment. This experiment is designed for the search for sterile neutrinos, and a muon tagging is an essential key component for the background rejection since the detector of the experiment is located over-ground, where is the 3rd floor of the J-PARC Material and Life experimental facility (MLF). Especially, stopping muons inside the detector create the Michel electrons, and they are important background to be rejected. Utilizing this innovative method, more than 99.8% of Michel electrons can be rejected even without a detector veto region. This technique can be employed for any experiments which uses the similar detector configurations.

physics.ins-det↗
arXiv2025

The first JSNS$^2$ measurement of electron neutrino flux using $^{12}C(ν_{e},e^{-}) ^{12}N_{g.s.}$ reaction

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment searching for sterile neutrinos through the observation of $\barν_μ \rightarrow \barν_e$ appearance oscillations, using neutrinos produced by muon decay-at-rest. A key aspect of the experiment involves accurately understanding the neutrino flux and the quantities of pions and muons, which are progenitors of (anti-)neutrinos, given that their production rates have yet to be measured. We present the first electron-neutrino flux measurement using $^{12}\mathrm{C}(ν_{e},e^{-}) ^{12}\mathrm{N}_{g.s.}$ reaction in JSNS$^2$, yielding a flux of (6.7 $\pm$ 1.6 (stat.) $\pm$ 1.7 (syst.)) $\times$ 10$^{-9}$ cm$^{-2}$ proton$^{-1}$ at the JSNS$^2$ detector location, located at 24 meters distance from the mercury target. This flux measurement is consistent with predictions from simulations based on hadron models.

hep-ex↗
arXiv2025

Measurement of radionuclide production probabilities in negative muon nuclear capture and validation of Monte Carlo simulation model

As part of the development of a sample radioactivity calculation program, we have measured radionuclide production probabilities in negative muon nuclear capture to update experimental data and to validate a calculation dataset obtained by a Monte Carlo simulation code. The probabilities have been obtained by an activation experiment on $^{27}$Al, $^\mathrm{nat}$Si, $^{59}$Co, and $^\mathrm{nat}$Ta targets. The obtained probabilities expand the validation scope to the radionuclide production processes outside of the existing data coverage. By comparing the resultant probabilities with the calculated dataset, it has been revealed that the dataset is generally on the {\color{black}safe} side in radioactivity estimation and needs to be corrected in the following three cases: (i) isomer production; (ii) radionuclide production by the multiple neutron emission; (iii) radionuclide production by particle emissions involving a proton. The present probabilities and the new findings on the correction provide valuable clues to improvements of the simulation models.

nucl-ex↗
arXiv2025

Lifetime measurement of the muonic atoms of enriched Si isotopes

Background: A muonic atom, composed of a negative muon and an atomic nucleus, undergoes two primary decay processes: muon-electron decay and muon nuclear capture. The branching ratio between these two processes can be determined from the measured lifetime of the muonic atom. While past researches have examined the general trend of muon capture rates across different nuclei, experimental and theoretical investigations into the isotope dependence of the lifetime remain limited. Purpose: The present study aims to measure the lifetimes of the muonic atom of isotopically enriched silicon isotopes. Methods: The experiment was conducted at the muon facility in the Material and Life Science Facility (MLF), J-PARC. A muon beam was stopped in various target materials, including isotopically enriched $^{28,29,30}$Si. The lifetimes of the muonic atoms were measured by detecting decay electrons using a $μ$SR spectrometer. The decay spectra were analyzed by fitting with multi-exponential functions to account for contributions from the target nucleus and surrounding materials. Results: For the first time, the lifetimes of the muonic atom of isotopically enriched $^{28,29,30}$Si were measured. Additionally, seven other targets were studied to validate the experimental method and analysis procedure. The results were compared with theoretical models such as Primakoff, Goulard-Primakoff, and the recently-developed microscopic and evaporation model (MEM). Conclusions: The Primakoff and Goulard-Primakoff formulas, while reproducing certain aspects of the isotope dependence, require further refinement. The comparison with MEM calculations constrains the axial vector ($g_A$) and induced pseudoscalar ($g_P$) coupling constants. The present experiment establishes a method for measuring the lifetimes of the muonic atom and will contribute to future systematic investigations.

nucl-ex↗
arXiv2025

PMT calibration for the JSNS2-II far detector with an embedded LED system

The JSNS2-II (the second phase of JSNS2, J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment aimed at searching for sterile neutrinos. This experiment has entered its second phase, employing two liquid scintillator detectors located at near and far positions from the neutrino source. Recently, the far detector of the experiment has been completed and is currently in the calibration phase. This paper presents a detailed description of the calibration process utilizing the LED system. The LED system of the far detector uses two Ultra-Violet (UV) LEDs, which are effective in calibrating all of PMTs at once. The UV light is converted into the visible light wavelengths inside liquid scintillator via the wavelength shifters, providing pseudo-isotropic light. The properties of all functioning Photo-Multiplier-Tubes (PMTs) to detect the neutrino events in the far detector, such as gain, its dependence of supplied High Voltage (HV), and Peak-to-Valley (PV) were calibrated. To achieve a good energy resolution for physics events, up to 10% of the relative gain adjustment is required for all functioning PMTs. This will be achieved using the measured HV curves and the LED calibration. The Peak-to-Valley (PV) ratio values are the similar to those from the production company, which distinguish the single photo-electron signal from the pedestal. Additionally, the precision of PMT signal timing is measured to be 2.1 ns, meeting the event reconstruction requirement of 10 ns.

physics.ins-det↗
arXiv2025

The Ladder and Readout Cables of Intermediate Silicon Strip Detector for sPHENIX

A new silicon-strip-type detector was developed for precise charged-particle tracking in the central rapidity region of heavy ion collisions. A new detector and collaboration at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory is sPHENIX, which is a major upgrade of the PHENIX detector. The intermediate tracker (INTT) is part of the advanced tracking system of the sPHENIX detector complex together with a CMOS monolithic-active-pixel-sensor based silicon-pixel vertex detector, a time-projection chamber, and a micromegas-based detector. The INTT detector is barrel shaped and comprises 56 silicon ladders. Two different types of strip sensors of 78~$μm$ pitch and 320~$μm$ thick are mounted on each half of a silicon ladder. Each strip sensor is segmented into 8$\times$2 and 5$\times$2 blocks with lengths of 16 and 20 mm. Strips are read out with a silicon strip-readout (FPHX) chip. In order to transmit massive data from the FPHX to the down stream readout electronics card (ROC), a series of long and high speed readout cables were developed. This document focuses on the silicon ladder, the readout cables, and the ROC of the INTT. The radiation hardness is studied for some parts of the INTT devices in the last part of this document, since the INTT employed some materials from the technology frontier of the industry whose radiation hardness is not necessarily well known.

physics.ins-det↗
arXiv2025

First Measurement of Missing Energy Due to Nuclear Effects in Monoenergetic Neutrino Charged Current Interactions

We present the first measurement of the missing energy due to nuclear effects in monoenergetic, muon neutrino charged-current interactions on carbon, originating from $K^+ \rightarrow μ^+ ν_μ$ decay at rest ($E_{ν_μ}=235.5$ MeV), performed with the J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source liquid scintillator based experiment. Toward characterizing the neutrino interaction, ostensibly $ν_μn \rightarrow μ^- p$ or $ν_μ$$^{12}\mathrm{C}$ $\rightarrow μ^-$$^{12}\mathrm{N}$, we define the missing energy as the energy transferred to the nucleus ($ω$) minus the kinetic energy of the outgoing proton(s), $E_{m} \equivω-\sum T_p$, and relate this to visible energy in the detector, $E_{m}=E_{ν_μ} (235.5 \mathrm{MeV})-m_μ(105.7 \mathrm{MeV}) + [m_n-m_p (1.3 \mathrm{MeV})] - E_{\mathrm{vis}}$. The missing energy, which is naively expected to be zero in the absence of nuclear effects (e.g. nucleon separation energy, Fermi momenta, and final-state interactions), is uniquely sensitive to many aspects of the interaction, and has previously been inaccessible with neutrinos. The shape-only, differential cross section measurement reported, based on a $(77\pm3)$% pure double-coincidence kaon decay-at-rest signal (621 total events), provides detailed insight into neutrino-nucleus interactions, allowing even the nuclear orbital shell of the struck nucleon to be inferred. The measurement provides an important benchmark for models and event generators at hundreds of MeV neutrino energies, characterized by the difficult-to-model transition region between neutrino-nucleus and neutrino-nucleon scattering, and relevant for applications in nuclear physics, neutrino oscillation measurements,and Type-II supernova studies.

hep-ex↗
arXiv2025

Performance studies of the CE-65v2 MAPS prototype structure

With the next upgrade of the ALICE inner tracking system (ITS3) as its primary focus, a set of small MAPS test structures have been developed in the 65 nm TPSCo CMOS process. The CE-65 focuses on the characterisation of the analogue charge collection properties of this technology. The latest iteration, the CE-65v2, was produced in different processes (standard, with a low-dose n-type blanket, and blanket with gap between pixels), pixel pitches (15, 18, 22.5 $μ$m), and pixel arrangements (square or staggered). The comparatively large pixel array size of $48\times24$ pixels in CE-65v2 allows the uniformity of the pixel response to be studied, among other benefits. The CE-65v2 chip was characterised in a test beam at the CERN SPS. A first analysis showed that hit efficiencies of $\geq 99\%$ and spatial resolution better than 5 $μ$m can be achieved for all pitches and process variants. For the standard process, thanks to larger charge sharing, even spatial resolutions below 3 $μ$m are reached, in line with vertex detector requirements for the FCC-ee. This contribution further investigates the data collected at the SPS test beam. Thanks to the large sensor size and efficient data collection, a large amount of statistics was collected, which allows for detailed in-pixel studies to see the efficiency and spatial resolution as a function of the hit position within the pixels. Again, different pitches and process variants are compared.

physics.ins-det↗
arXiv2025

Pulse Shape Discrimination in JSNS$^2$

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of $\barν_μ \rightarrow \barν_e$ appearance oscillations using neutrinos with muon decay-at-rest. For this search, rejecting cosmic-ray-induced neutron events by Pulse Shape Discrimination (PSD) is essential because the JSNS$^2$ detector is located above ground, on the third floor of the building. We have achieved 95$\%$ rejection of neutron events while keeping 90$\%$ of signal, electron-like events using a data driven likelihood method.

physics.ins-det↗
arXiv2025

Evaluation of the performance of the event reconstruction algorithms in the JSNS$^2$ experiment using a $^{252}$Cf calibration source

JSNS$^2$ searches for short baseline neutrino oscillations with a baseline of 24~meters and a target of 17~tonnes of the Gd-loaded liquid scintillator. The correct algorithm on the event reconstruction of events, which determines the position and energy of neutrino interactions in the detector, are essential for the physics analysis of the data from the experiment. Therefore, the performance of the event reconstruction is carefully checked with calibrations using $^{252}$Cf source. This manuscript describes the methodology and the performance of the event reconstruction.

hep-ex↗
arXiv2024

Isochronous mass spectrometry at the RIKEN Rare-RI Ring facility

A dedicated isochronous storage ring, named the Rare-RI Ring, was constructed at the RI Beam Factory of RIKEN, aiming at precision mass measurements of nuclei located in uncharted territories of the nuclear chart. The Rare-RI Ring employs the isochronous mass spectrometry technique with the goal to achieve a relative mass precision of $10^{-6}$ within a measurement time of less than 1 ms. The performance of the facility was demonstrated through mass measurements of neutron-rich nuclei with well-known masses. Velocity or magnetic rigidity is measured for every particle prior to its injection into the ring, wherein its revolution time is accurately determined. The latter quantity is used to determine the mass of the particle, while the former one is needed for non-isochronicity corrections. Mass precisions on the order of $10^{-5}$ were achieved in the first commissioning, which demonstrates that Rare-RI Ring is a powerful tool for mass spectrometry of short-lived nuclei.

nucl-ex↗
arXiv2024

Study on the accidental background of the JSNS$^2$ experiment

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment which searches for sterile neutrinos via the observation of $\barν_μ \to \barν_{e}$ appearance oscillations using muon decay-at-rest neutrinos. The data taking of JSNS$^2$ have been performed from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is (9.29$\pm 0.39) \times 10^{-8}$ / spill with 0.75 MW beam power and comparable to the number of searching signals.

hep-ex↗
arXiv2023

The acrylic vessel for JSNS$^{2}$-II neutrino target

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment designed for the search for sterile neutrinos. The experiment is currently at the stage of the second phase named JSNS$^{2}$-II with two detectors at near and far locations from the neutrino source. One of the key components of the experiment is an acrylic vessel, that is used for the target volume for the detection of the anti-neutrinos. The specifications, design, and measured properties of the acrylic vessel are described.

hep-ex↗