arXiv subjects

Masaya Ichikawa

Publications and source records attributed to Masaya Ichikawa.

8 recordsLinked to original sources

arXiv2026

AI's Capability in Assisting Scientific Research in Physics, Astrophysics, and Cosmology I: Literature Review

We investigate how well large language models (LLMs) can assist with literature reviews for scientific research. We perform a controlled study of eight expert-conceived research projects across the areas of physics, astrophysics, and cosmology. Each project has a defined background and goal, and human experts and AI prompters are asked to perform identical literature review tasks in parallel. We compare the relevant literature selected by humans with that selected by mid-2025 LLMs (ChatGPT-4o, ChatGPT Deep Research, and Gemini). We find the overlap between human- and AI-selected references to be small ($<$6\%), indicating that AI models do not yet reproduce a competent expert search on their own, though they have the potential to complement literature searches by humans. We then assess the reliability and completeness of AI-generated candidate references, distinguishing two types of hallucination: fabrications (references to nonexistent papers) and metadata mismatches (real papers with one or more incorrect fields). We find that while fabricated references make up 3\% of the AI-generated references, 64\% are real papers with at least one incorrect field (title, author, year, journal, DOI, or link), indicating that the mid-2025 models require systematic verification. However, the performance is significantly improved for the 2026 model ChatGPT Pro 5.5, with a single-project test showing zero fabrication or metadata mismatches.

astro-ph.IM↗

arXiv2026

AI's Capability in Assisting Scientific Research in Physics, Astrophysics, and Cosmology II: Project Planning and Proposal Evaluation

We investigate how well large language models (LLMs) can assist scientific project planning and proposal evaluation. One-page project plans were independently generated for eight expert-conceived research projects in physics, astrophysics, and cosmology by human researchers and three contemporary LLMs (ChatGPT, Claude, and DeepSeek; mid-2025 models, used with their default tool access). The resulting 32 proposals were blindly evaluated by four human reviewers and two newer frontier LLMs (Claude Opus 4.8 and ChatGPT Pro 5.5) using a four-aspect evaluation rubric. Reviewers were also asked to identify whether each proposal was written by a human or an AI. Human reviewers rated human- and AI-written proposals similarly overall, whereas both AI reviewers scored AI-written proposals about one point higher (on a five-point scale) than human-written proposals. Human reviewers correctly identified human- and AI-written proposals 72% and 79% of the time, respectively, while both AI reviewers correctly classified all 32 proposals (100%). These results suggest that current LLMs can produce project plans comparable to human-written ones in the eyes of human reviewers, but that AI reviewers show a systematic preference for AI-generated proposals. Our results suggest caution when deploying LLMs widely in proposal preparation and evaluation.

cs.CL↗

arXiv2026

The Environmental Dependence of Halo Intrinsic Alignments: Stronger Signals in Underdense Regions

The intrinsic alignment (IA) of galaxies and the dark matter haloes that host them is one of the leading astrophysical systematics for weak-lensing cosmology, yet how the IA signal depends on the large-scale environment in which haloes reside is not yet fully characterised. We use the high-resolution $N$-body simulations of the Dark Quest suite to measure the environmental dependence of the IA of dark matter haloes over the redshift range $z=0.1$--$1.5$. We quantify each halo's environment through the overdensity $δ_8$, defined from the number of neighbouring haloes within $8\, h^{-1}Mpc$, and we isolate the environmental effect from its degeneracy with the halo-mass dependence by comparing the most overdense and most underdense haloes constructed to share the same halo-mass distribution. We find that haloes in underdense environments exhibit systematically larger IA amplitudes $A_{\rm IA}$ than haloes of the same mass in overdense environments, by a factor of $\sim1.5$--$1.8$, and that this trend persists across the mass and redshift ranges probed, strengthening towards low redshift. Using an orientation-only (unit-ellipticity) estimator, we further show that this environmental contrast is driven by a combination of two effects: haloes in underdense regions are both intrinsically less spherical and more strongly aligned with the large-scale tidal field than their overdense counterparts of the same mass. These results indicate that the large-scale environment is a non-negligible variable in modelling halo and galaxy alignments, and may be a particularly important factor for beyond-two-point weak-lensing analyses.

astro-ph.CO↗

arXiv2026

The Silicon Tracking System of the E16 experiment at J-PARC: construction, installation and commissioning in beam test experiments

The J-PARC E16 experiment aims to search for signatures of chiral symmetry restoration. It studies in-medium modifications of vector mesons that decay via the dielectron channel. The measurements use a high-intensity 30 GeV proton beam with C and Cu targets at rates up to 10 MHz. To achieve this, the experiment upgrades its tracking, by introducing innermost detector modules constructed with the same technology and procedures as the modules of the Silicon Tracking System (STS) of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiproton and Ion Research (FAIR). A total of 15 modules were assembled, tested, characterized and then installed in the E16 detector setup. The detector was commissioned in a beam test experiment at Tsukuba, where the detector modules could be exposed to a 3 GeV electron beam. In preparation for the beam test the modules were characterized and calibrated, and performance studies were accomplished to assess the quality of the setup. During beamtime, three modules were operated and illuminated in two planes by the electron beam. This paper presents the results of the construction, characterization, commissioning, and operation of the E16-STS modules in beam test experiments.

physics.ins-det↗

arXiv2026

First measurement of $ϕ$ meson production in 30 GeV proton-nucleus reactions via di-electron decay at J-PARC

We present the first measurement of the production of the $ϕ$ meson in 30 GeV proton-nucleus interactions on carbon and copper targets via the di-electron decay channel. The measurement was conducted at the high-momentum beamline of the J-PARC Hadron Experimental Facility, which was commissioned in 2020. The $e^+e^-$ pairs were detected using the E16 spectrometer, during a commissioning run of the J-PARC E16 experiment. The $ϕ$ mesons are successfully reconstructed on all experimental targets. The obtained yields are converted to the total production cross section, assuming a kinematical distribution of the event generator JAM. The total cross sections derived are 2.0 $\pm$ 0.9 (stat.) $\pm$ 1.0 (syst.) mb on the carbon target and 10.3 $\pm$ 4.4 (stat.) $\pm$ 4.4 (syst.) mb on the copper target. The mass-number dependence of the cross section is discussed using the parameter $α$, defined as $σ\propto A^α$, resulting in $α= $ 0.99 $\pm$ 0.38 (stat.) $\pm$ 0.34 (syst.). The extrapolation to $A=1$, which means that the cross section of proton-proton reactions, is in good agreement with the existing measurements at comparable energies.

nucl-ex↗

arXiv2025

Analysis of spectral modification of $ϕ$ mesons at finite density using a transport approach in the 12 GeV pA reactions

The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of phi mesons inside and outside nuclei were measured using 12 GeV pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the phi meson peak in the data for slow-moving phi mesons ($βγ=p_ϕ/m_ϕ<1.25$) with the Cu target, and in-medium vector meson spectral modification was verified. We newly employed the PHSD transport approach to take into account the time evolution of spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving $ϕ$ mesons with the Cu target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

nucl-ex↗

arXiv2024

Production and in-medium modification of $ϕ$ mesons in proton-nucleus reactions from a transport approach

Production and in-medium modification of hidden strange $ϕ$ mesons are studied in proton-nucleus reactions - p+C, p+Cu and p+Pb - at 12 GeV/c, partially measured by the KEK E325 collaboration via the dilepton decay mode. This work is based on the off-shell microscopic Parton-Hadron-String Dynamics (PHSD) transport approach, which provides the dynamical description of strongly interacting hadronic and partonic degrees of freedom in dense matter, and especially makes it possible to simulate in-medium off-shell dynamics of the $ϕ$ meson in the reactions studied. Different in-medium scenarios for the modification of the $ϕ$ meson spectral function in nuclear matter are investigated: i) dropping pole mass, ii) collisional broadening and iii) simultaneous dropping pole mass and collisional broadening. Even though the $ϕ$ meson production in p+A reactions occurs only at densities around or below normal nuclear matter density $ρ_0$, we find visible modifications of the generated dilepton spectra for the in-medium scenarios compared to the vacuum distribution.

hep-ph↗

arXiv2020

Data acquisition system in Run-0a for the J-PARC E16 experiment

J-PARC E16 is an experiment to examine the origin of hadron mass through a systematic measurement of spectral changes of vector mesons in nuclei. The measurement of $e^{+}e^{-}$ pairs from the decay of vector mesons will provide the information of the partial restoration of the chiral symmetry in a normal nuclear density. To resolve a pulse pile-up and achieve good discrimination of $e^{\pm}$ from the background of a reaction rate of an order of 10 MHz, the data acquisition (DAQ) system uses waveform sampling chips of APV25 and DRS4. The trigger rate and data rate are expected to be 1 kHz and 130--330 MiB/s, respectively. The DAQ system for readout of APV25 and DRS4 were developed, where events were synchronized by common trigger and tag data. The first commissioning in beam, called Run-0a, was performed in June 2020 with about 1/4 of the designed setup. The DAQ worked with a trigger rate of 300 Hz in the Run-0a and the main bottleneck was a large data size of APV25. Further optimization of the DAQ system will improve the performance.

physics.ins-det↗