arXiv subjects

Sho Nagao

Publications and source records attributed to Sho Nagao.

5 recordsLinked to original sources

arXiv2026

Response to the $^7_\Lambda$He interpretation of MAMI's recent determination of $B_\Lambda(^3_\Lambda$H)

We respond to the recent suggestion by A. Gal [arXiv:2604.18259] that the sharp pion-momentum peak at $p_{\pi^-} \approx 113.8$~MeV/$c$ observed in our $^7\mathrm{Li}(e,e^\prime K^+)$ electroproduction experiment at MAMI [Phys. Rev. Lett. 136, 152301 (2026)] originates from $^7_\Lambda\mathrm{He}$ weak decay rather than from $^3_\Lambda\mathrm{H} \to \pi^- + {}^3\mathrm{He}$ as we reported. We present quantitative arguments against this interpretation and conclude that the $^3_\Lambda\mathrm{H}$ assignment remains the most well-supported interpretation of the data.

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arXiv2026

Precise measurement of the $Λ$-binding energy difference between $^3_Λ$H and $^4_Λ$H via decay-pion spectroscopy at MAMI

We performed high-precision decay-pion spectroscopy of light $Λ$ hypernuclei at the Mainz Microtron (MAMI) using the A1 spectrometer facility. By measuring the monochromatic $π^-$ momentum from the two-body weak decay $^3_Λ\mathrm{H} \to {}^3\mathrm{He} + π^-$ and referencing it to the $^4_Λ\mathrm{H} \to {}^4\mathrm{He} + π^-$ decay, we determined the $Λ$ binding energy of $^3_Λ\mathrm{H}$ with unprecedented accuracy. The obtained value, $B_Λ(^3_Λ\mathrm{H}) = 0.523 \pm 0.013~(\mathrm{stat.}) \pm 0.075~(\mathrm{syst.})$~MeV, is consistent with the STAR result, but indicates a significantly deeper binding than inferred from earlier measurements. This result implies a stronger $Λ$-deuteron interaction and provides stringent constraints on hyperon-nucleon interactions.

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arXiv2025

Measurement of $\rm ^{6}H$ ground state energy in an electron scattering experiment at MAMI-A1

For the first time the neutron-rich hydrogen isotope $\rm ^{6}H$ was produced in an electron scattering experiment in the reaction $\rm ^{7}Li(e,~e'pπ^{+})^{6}H$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the scattered electron, the produced proton, and $π^{+}$, the missing mass spectrum of $\rm ^{6}H$ was obtained. A clear peak above $^3$H+n+n+n energy threshold was seen resulting in a ground state energy of $\rm ^{6}H$ at $2.3\pm0.5({\rm stat.})\pm0.4({\rm syst.})$ MeV with a width of $1.9\pm1.0({\rm stat.})\pm0.4({\rm syst.})$ MeV. This work challenges the understandings of multi-nucleon interactions and presents a new method to study light neutron-rich nuclei with electron scattering experiments.

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arXiv2024

Development of a real-time beam profile monitor for GeV photons and its application in accelerator facilities

A real-time beam profile monitoring system is proposed for GeV photon beams at the BM4 beamline of the Mikamine site, Research Center for Accelerator and Radioisotope Science (RARiS; previously known as ELPH) at Tohoku University. This monitoring system enhances the capability to monitor the entire beamline by incorporating newly developed beam profile monitors (BPMs) for upstream and midstream sections, in addition to the existing high-speed BPM used for downstream monitoring. This paper reports on the detection mechanisms of the newly developed BPMs and the actual measurement results obtained using the integrated beam monitoring system. The new BPMs are composed of plastic scintillation fibers and silicon photomultipliers, enabling high-precision, real-time measurements. Data acquisition utilizes streaming TDC, a firmware commonly employed in the J-PARC Hadron-hall, allowing real-time detection of high-intensity photon beams with count rates reaching several tens of MHz. With sufficient statistical data, the BPM achieved a 1-s beam-profiling accuracy of 10 μm. The proposed BPM system serves as a valuable resource for future physics experiments at the BM4 photon beamline and will significantly contribute to ongoing accelerator research endeavors.

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arXiv2021

Extension of the J-PARC Hadron Experimental Facility: Third White Paper

The J-PARC Hadron Experimental Facility was constructed with an aim to explore the origin and evolution of matter in the universe through the experiments with intense particle beams. In the past decade, many results on particle and nuclear physics have been obtained at the present facility. To expand the physics programs to unexplored regions never achieved, the extension project of the Hadron Experimental Facility has been extensively discussed. This white paper presents the physics of the extension of the Hadron Experimental Facility for resolving the issues in the fields of the strangeness nuclear physics, hadron physics, and flavor physics.

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