arXiv subjects

Takatsugu Ishikawa

Publications and source records attributed to Takatsugu Ishikawa.

6 recordsLinked to original sources

arXiv2026

Feasibility demonstration of a high-momentum, high-purity muon beamline at the J-PARC Hadron Experimental Facility

We have established and characterized a novel high-purity muon beam delivery scheme, designated as $μ$20, at the high-momentum hadron beamline (B-line) of the J-PARC Hadron Experimental Facility. This scheme delivers tertiary muons produced via the in-flight backward decays of secondary pions in the straight section of the beamline, inherently suppressing parent hadron contamination. In a systematic performance evaluation, the muon beam achieved a standalone intensity of $1.7\times10{^3}$ particles/spill with a spatial spread (standard deviation, $σ$) of approximately 15 mm at the downstream detector position. A systematic attenuation analysis utilizing an iron absorber verified a high muon purity of 98.0$\pm$0.6% for the 3 GeV/$c$ muon beam mode. Crucially, this work marks the first successful feasibility study of a high-momentum and high-purity muon beamline operation at an experimental facility in Japan.

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arXiv2024

$K^-d\rightarrowπΛN$ reaction with in-flight kaons for studying the $ΛN$ interaction

The $ΛN$ invariant mass spectra for the reactions $K^-d\rightarrowπ^-Λp$ and $K^-d\rightarrowπ^0Λn$ are calculated for experimental study of isospin symmetry breaking in the $ΛN$ scattering at low energies, the difference in the scattering lengths and effective ranges of $Λp$ and $Λn$ systems. The calculations are performed for in-flight kaons with a momentum of 1000 MeV/c with employing partial wave analysis up to the p-wave for meson-baryon amplitudes and the spin-flip term for baryon-baryon amplitudes. Kinematic selection is utilized to suppress the background processes by selecting forward-emitting pions and higher momentum nucleons. It is worth noting that isospin symmetry breaking in the $ΛN$ system can be extracted from the difference of the $ΛN$ invariant mass spectra between the $K^-d\rightarrowπ^-Λp$ and $K^-d\rightarrowπ^0Λn$ reactions.

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arXiv2022

$K^- d\rightarrow πΛN$ reaction for studying charge symmetry breaking in the $ΛN$ interaction

We discuss charge symmetry breaking in the $ΛN$ interaction. In order to investigate the $Λp$ and $Λn$ interactions at low energies, we propose to utilize the $K^-d\to π^-Λp$ and $K^-d\to π^0Λn$ reactions. They are symmetric under the exchange of both the pion and nucleon isospin partners in the final states. This advantage allows us to study charge symmetry breaking in the $ΛN$ interaction. We calculate the differential cross sections of these reactions with stopped kaons theoretically and discuss the possibility to extract the scattering length and effective range of the $ΛN$ scattering. With stopped kaons, the $ΛN$ interaction takes place dominantly in the spin-triplet state thanks to the deuteron spin and $s$-wave dominance of the scattering amplitudes at the low energy. We find that the ratio of the differential cross sections as a function of the $ΛN$ invariant mass between the two reactions is useful for revealing how charge symmetry breaking, or isospin symmetry breaking appears in the low-energy $ΛN$ scattering.

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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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arXiv2020

Neutron-neutron scattering length from $π^+$ photoproduction on the deuteron

We discuss the possibility of extracting the neutron-neutron scattering length $a_{nn}$ and effective range $r_{nn}$ from cross section data ($d^2σ/dM_{nn}/dΩ_π$), as a function of the $nn$ invariant mass $M_{nn}$, for $π^+$ photoproduction on the deuteron ($γd\to π^+nn$). The analysis is based on a $γd\to π^+nn$ reaction model in which realistic elementary amplitudes for $γp\to π^+n$, $NN\to NN$, and $πN\to πN$ are built in. We show that $M_{nn}$ dependence (lineshape) of a ratio $R_{\rm th}$, $d^2σ/dM_{nn}/dΩ_π$ normalized by $dσ/dΩ_π$ for $γp\toπ^+ n$ and the nucleon momentum distribution inside the deuteron, at the kinematics with $θ_π=0^\circ$ and $E_γ\sim 250$ MeV is particularly useful for extracting $a_{nn}$ and $r_{nn}$ from the corresponding data $R_{\rm exp}$. It is found that $R_{\rm exp}$ with 2% error, resolved into the $M_{nn}$ bin width of 0.04 MeV (corresponding to the $p_π$ bin width of 0.05 MeV$/c$), can determine $a_{nn}$ and $r_{nn}$ with uncertainties of $\pm 0.21$ fm and $\pm 0.06$ fm, respectively, for the case of $a_{nn}=-18.9$ fm and $r_{nn}=2.75$ fm. The requirement of such narrow bin widths indicates that the momenta of the incident photon and the emitted $π^+$ have to be measured with high resolutions. This can be achieved by utilizing virtual photons of very small $Q^2$ from electron scattering at Mainz MAMI facility. The proposed method for determining $a_{nn}$ and $r_{nn}$ from $γd\to π^+ nn$ has a great experimental advantage over the previous one utilizing $π^- d\toγnn$ for being free from the formidable task of controlling the neutron detection efficiency and its uncertainty.

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arXiv2018

Possible $η' d$ bound state and its $s$-channel formation in the $γd \to ηd$ reaction

We theoretically investigate a possibility of an $η^{\prime} d$ bound state and its formation in the $γd \to ηd$ reaction. First, in the fixed center approximation to the Faddeev equations we obtain an $η^{\prime} d$ bound state with a binding energy of 25 MeV and width of 19 MeV, where we take the $η^{\prime} N$ interaction with a coupling to the $ηN$ channel from the linear $σ$ model. Then, in order to investigate the feasibility from an experimental point of view, we calculate the cross section of the $γd \to ηd$ reaction at the photon energy in the laboratory frame around 1.2 GeV. As a result, we find a clear peak structure with the strength $\sim$ 0.2 nb/sr, corresponding to a signal of the $η^{\prime} d$ bound state in case of backward $η$ emission. This structure will be prominent because a background contribution coming from single-step $η$ emission off a bound nucleon is highly suppressed. In addition, the signal can be seen even in case of forward $η$ emission as a bump or dip, depending on the relative phase between the bound-state formation and the single-step background.

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