arXiv subjects

T. N. Takahashi

Publications and source records attributed to T. N. Takahashi.

12 recordsLinked to original sources

arXiv2025

Measurement of $Λ$ Polarization in the $π^{-}p \to K^{0} Λ$ Reaction at $p_{π^{-}}=1.33$ GeV/$c$ toward a New $Λp$ Scattering Experiment

This paper presents high-precision experimental data of the polarization of the $Λ$ hyperon in the $π^{-}p \to K^{0} Λ$ reaction, measured in the angular range $0.6<\cos θ^{CM}_{K0}<1.0$ with a fine bin width of $d\cos θ^{CM}_{K0}=0.05$. The data were obtained from the J-PARC E40 experiment at the K1.8 beamline in the J-PARC Hadron Experimental Facility. The observed average polarization of $Λ$ in the range $0.60<\cos θ^{CM}_{K0}<0.85$ was $0.932 \pm 0.058 \,(\text{stat}) \pm 0.028 \,(\text{syst})$, demonstrating the successful extraction of precise polarization observables. This result provides essential experimental input for partial wave analysis (PWA) of dynamical coupled-channel (DCC) models, which aim to uncover the underlying mechanisms of $N^{*}$ resonances that emerge in intermediate states of $πN$ and $γN$ interactions. Besides, it indicates the feasibility of a strongly polarized $Λ$ beam suitable for future $Λp$ scattering experiments (e.g., J-PARC E86).

nucl-ex↗

arXiv2022

Measurement of differential cross sections for $Σ^+p$ elastic scattering in the momentum range 0.44-0.80 GeV/c

We performed a novel $Σ^+ p$ scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 $Σ^+ p$ elastic scattering events were identified from $4.9 \times 10^7$ tagged $Σ^+$ particles in the $Σ^+$ momentum range 0.44 -- 0.80 GeV/$c$. The differential cross sections of the $Σ^+ p$ elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the $^3 S_1$ and $^1 P_1$ channels for the first time. The phase shift of the $^3 S_1$ channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as $20^\circ<|δ_{^3S_1}|<35^\circ$. If the sign of $δ_{^3S_1}$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted.

nucl-ex↗

arXiv2022

Precise measurement of differential cross sections of the Σ-p --> Λ n reaction in momentum range 470-650 MeV/c

The differential cross sections of the Σ-p --> Λ n reaction were measured accurately for the Σ- momentum (p_{Σ}) ranging from 470 to 650 MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the Σ-p --> Λ n reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of Δcosθ = 0.1. The obtained differential cross sections show slightly forward-peaking structure in the measured momentum regions.The cross sections integrated for -0.7 < cosθ < 1.0 were obtained as 22.5 +- 0.68 (stat.) +- 0.65 (syst.) mb and 15.8 +-0.83(stat.) +- 0.52 (syst.) mb for 470<p_{Σ}(MeV/c)<550 and 550<p_{Σ}(MeV/c)<650, respectively. These results show a drastic improvement compared to past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

nucl-ex↗

arXiv2021

Measurement of the differential cross sections of the Sigma-p elastic scattering in momentum range of 470 to 850 MeV/c

A high statistics $Σp$ scattering experiment has been performed at the J-PARC Hadron Experimental Facility. Data for momentum-tagged $Σ^{-}$ running in a liquid hydrogen target were accumulated by detecting the $π^{-}p \to K^{+}Σ^{-}$ reaction with a high intensity $π^{-}$ beam of 20 M/spill. Differential cross sections of the $Σ^{-}p$ elastic scattering were derived with a drastically improved accuracy by identifying the largest statistics of about 4,500 events from 1.72 $\times$ $10^{7}$ $Σ^{-}$. The derived differential cross section shows a clear forward-peaking angular distribution for a $Σ^{-}$ momentum range from 470 to 850 MeV/$c$. The accurate data will impose a strong constraint on the theoretical models of the baryon-baryon interactions.

nucl-ex↗

arXiv2019

Write-ups for workshop on the project for the hadron experimental facility of J-PARC, Partial collection of LOIs at the extended hadron hall and the related topics

This write-up document is a summary of International workshop on the project for the extended hadron experimental facility which was held from March 26 to 28, 2018 at KEK Tokai Campus. This document is a collection of Letter Of Intents (LOIs) related to the proposed beam lines in the extended hadron experimental facility at J-PARC.

nucl-ex↗

arXiv2018

Trigger Merging Module for the J-PARC E16 Experiment

An experiment to measure an invariant mass of ϕ mesons in nuclear medium is planned as the J-PARC E16 experiment. A trigger merging module (TRG-MRG) has been developed to detect leading-edges from 256 channels of discriminator-output signals and transmit those serialized hit data to trigger decision module with four optical links. The result of the test shows enough performance of the TRG-MRG as 1 ns TDC and data multiplexer with four 6.25 Gbps transceivers.

physics.ins-det↗

arXiv2017

Missing-mass spectroscopy with the ${}^{6}$Li($π^{-}, K^{+}$)X reaction to search for ${}^{6}_Λ$H

We searched for the bound state of the neutron-rich $Λ$-hypernucleus ${}^{6}_Λ$H, using the ${}^{6}$Li($π^{-}, K^{+}$)X double charge-exchange reaction at a $π^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4 \times 10^{12}$ $π^{-}$ was driven onto a ${}^{6}$Li target of 3.5-g/$\rm cm^2$ thickness. No event was observed below the bound threshold, i.e., the mass of ${}^{4}_Λ$H + 2n, in the missing-mass spectrum of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction in the $2^{\circ}$ < $θ_{πK}$ < $20^{\circ}$ angular range. Furthermore, no event was found up to 2.8 MeV/$c^2$ above the bound threshold. We obtained the the double-differential cross section spectra of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction in the angular range of $2^{\circ}$ < $θ_{πK}$ < $14^{\circ}$. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the ${}^{6}_Λ$H hypernucleus bound state. In addition, not only the bound state region, but also the $Λ$ continuum region and part of the $Σ^{-}$ quasi-free production region of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction, were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the $Σ^{-}$-nucleus optical potential for $Σ^{-}$-${}^{5}$He through spectrum shape analysis.

nucl-ex↗

arXiv2015

Precise determination of $^{12}_Λ$C level structure by $γ$-ray spectroscopy

Level structure of the $^{12}_Λ$C hypernucleus was precisely determined by means of $γ$-ray spectroscopy. We identified four $γ$-ray transitions via the $^{12}$C$(π^{+},K^{+}γ)$ reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet $(2^{-}_{1},1^{-}_{1})$ was measured to be $161.5\pm0.3\text{(stat)}\pm0.3\text{(syst)}$\,keV from the direct $M1$ transition. Excitation energies of the $1^{-}_{2}$ and $1^{-}_{3}$ states were measured to be $2832\pm3\pm4$\,keV and $6050\pm8\pm7$\,keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $Λ$ hypernuclei.

nucl-ex↗

arXiv2014

High-resolution search for the $Θ^{+}$ pentaquark via a pion-induced reaction at J-PARC

The pentaquark $Θ^+$ has been searched for via the $π^-p \to K^-X$ reaction with beam momenta of 1.92 and 2.01 GeV/$c$ at J-PARC. A missing mass resolution of 2 MeV (FWHM) was achieved but no sharp peak structure was observed. The upper limits on the production cross section averaged over the scattering angle from 2$^{\circ}$ to 15$^{\circ}$ in the laboratory frame were found to be less than 0.28 $μ$b/sr at the 90\% confidence level for both the 1.92- and 2.01-GeV/$c$ data. The systematic uncertainty of the upper limits was controlled within 10\%. Constraints on the $Θ^+$ decay width were also evaluated with a theoretical calculation using effective Lagrangian. The present result implies that the width should be less than 0.36 and 1.9 MeV for the spin-parity of $1/2^+$ and $1/2^-$, respectively.

nucl-ex↗

arXiv2014

Search for $^6_Λ$H hypernucleus by the $^6$Li$(π^-,K^+)$ reaction at $p_{π^-}$ = 1.2 GeV/$c$

We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_Λ$H, by the $^6$Li($π^-,K^+$) reaction at $p_{π^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $^6_Λ$H hypernucleus neither below nor above the $^4_Λ$H$+2n$ particle decay threshold. An upper limit of the production cross section for the bound $^6_Λ$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.

nucl-ex↗

arXiv2012

Search for the $Θ^{+}$ pentaquark via the $π^-p\to K^-X$ reaction at 1.92 GeV/$c$

The $Θ^+$ pentaquark baryon was searched for via the $π^-p\to K^-X$ reaction in a missing-mass resolution of 1.4 MeV/$c^2$(FWHM) at J-PARC. $π^-$ meson beams were incident on the liquid hydrogen target with the beam momentum of 1.92 GeV/$c$. No peak structure corresponding to the $Θ^+$ mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2$^{\circ}$ to 15$^{\circ}$ in the laboratory frame was obtained to be 0.26 $μ$b/sr in the mass region of 1.51$-$1.55 GeV/$c^2$.The upper limit of the $Θ^+$ decay width using the effective Lagrangian approach was obtained to be 0.72 MeV/$c^2$ and 3.1 MeV/$c^2$ for $J^P_Θ=1/2^+$ and $J^P_Θ=1/2^-$, respectively.

nucl-ex↗

arXiv2009

Production of Neutron-Rich Lambda Hypernuclei at J-PARC

We discuss the usefulness of the double charge-exchange reactions (DCX) for the production of the neutron-rich Lambda-hypernuclei. We believe the (pi-,K+) reaction is one of the most promising DCX reactions, and propose to produce the neutron-rich Lambda-hypernuclei, 6(Lambda)H and 9(Lambda)He, at the J-PARC 50 GeV PS by the reaction (J-PARC E10 experiment). The design of the experiment is presented.

nucl-ex↗