Σ⁺p弾性散乱の微分断面積測定および位相差解析

京都大学新制・課程博士博士(理学)甲第24408号理博第4907号新制||理||1701(附属図書館)京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 永江 知文, 准教授 成木 恵, 教授 橋本 幸士学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC

Tetraneutron ($^4n$) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. $^4\mathrm{He}({\pi}^- , {\pi}^+)$, as an alternative way to populate tetraneutron. An intense ${\pi}^-$ beam with the kinetic energy of ~850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, will open up a possibility to improve the experimental sensitivity of the formation cross section, which will be much smaller than hitherto known DCX cross sections such as $^9\mathrm{Be}({\pi}^-, {\pi}^+)^9\mathrm{He}\ (g.s.)$.Comment: 4 pages, 1 figure; proceedings of the 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto, Japan, 25-30 July 201

Λ polarization measurement of the

We performed the J-PARC E40 experiment to measure the Σp scattering cross sections from 2018 to 2020. Together with the π−p → K+Σ− data, the π−p → K0Λ data were accumulated as a byproduct. The analysis confirmed that Λ could be identified with an S/N ratio of ∼ 2.67. The polarization of Λ(PΛ) was preliminarily derived as 1.009 ± 0.049 for the K0 angular range of 0.7 < cos θK0, CM < 0.8. It is more accurate than the past data [1]. The high polarization enables us to measure not only the differential cross section but also spin observables of the Λp scattering in the future J-PARC experiment

Results of analysis of Σ

We performed a novel Σ+p scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 Σ+p scattering events were identified by a kinematical consistency check for the recoil proton. The differential cross sections of the Σ+p elastic scattering were derived with better precision than in previous experiments. By exploiting high-quality differential cross section data and the simple representation of Σ+p interaction in the SU(3) flavor symmetry, we performed a phase-shift analysis on hyperon-nucleon scattering data for the first time. The absolute value of the phase shift of the 3S1 channel, where a large repulsive force was predicted due to the Pauli exclusive effect between quarks, was evaluated. These results indicate that the interaction of the 3S1 channel in the Σ+p channel is moderately repulsive, as the Nijmegen extended-soft-core models predicted

Direct measurement of the

The cross sections of the 7Be(n, α)4He reaction for p-wave neutrons were experimentally determined at Ec.m. = 0.20−0.81 MeV close to the Big Bang nucleosynthesis (BBN) energy window for the first time on the basis of the detailed balance principle by measuring the time-reverse reaction. The obtained cross sections are much larger than the cross sections for s-wave neutrons inferred from the recent measurement at the n_TOF facility in CERN, but significantly smaller than the theoretical estimation widely used in the BBN calculations. The present results suggest the 7Be(n, α)4 He reaction rate is not large enough to solve the cosmological lithium proble

Direct measurement of the 7Be(n, α)4 He reaction cross sections for the cosmological Li problem

The cross sections of the 7Be(n, α)4He reaction for p-wave neutrons were experimentally determined at Ec.m. = 0.20−0.81 MeV close to the Big Bang nucleosynthesis (BBN) energy window for the first time on the basis of the detailed balance principle by measuring the time-reverse reaction. The obtained cross sections are much larger than the cross sections for s-wave neutrons inferred from the recent measurement at the n_TOF facility in CERN, but significantly smaller than the theoretical estimation widely used in the BBN calculations. The present results suggest the 7Be(n, α)4 He reaction rate is not large enough to solve the cosmological lithium proble

High resolution spectroscopy of the “Σ

We present a new proposal, J-PARC E90, to measure a missing-mass spectrum near the ΣN threshold for the d(K−, π−) reactions at 1.4 GeV/c. While many previous experiments support apparent enhancement near the ΣN thresh-old, the dynamical origin of this so-called “ΣN cusp” remains yet unsolved. The enhancement suggests either a cusp structure or a weakly bound state. One of the keys to making it clear is improving the missing-mass resolution and statistics. Our new experiment can achieve the missing-mass resolution of 0.4 MeV in σ using the K1.8 beam line and S-2S spectrometers at J-PARC. Further-more, we can suppress quasi-free background processes with the time projection chamber (HypTPC), which operated nicely for the H-dibaryon search experi-ment (J-PARC E42). The J-PARC E90 aims to extract the scattering length of the ΣN system with isospin T = 1/2 and spin-triplet channels