Repulsion and absorption of the Σ\Sigma-nucleus potential for Σ−\Sigma^--5^5He in the 6^6Li(π−\pi^-, K+K^+) reaction

We study phenomenologically inclusive spectra of the $^6$Li($\pi^-$, $K^+$) reaction at 1.2 GeV/$c$ within a distorted-wave impulse approximation with the optimal Fermi-averaging $\pi^- p \to K^+ \Sigma^-$ $t$ matrix. We attempt to clarify the property of a $\Sigma$-nucleus potential for $\Sigma^-$-$^5$He by comparing the calculated spectra with the data of the J-PARC E10 experiment. The result shows that the repulsive and absorptive components of the $\Sigma^-$-$^5$He potential provide the ability to explain the data of the continuum spectra in $\Sigma$ and $\Lambda$ regions; the strengths of $V_\Sigma \simeq$ +30 MeV and $W_\Sigma \simeq$ $-$26 MeV are favored within the Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of the size and potential range for $\Sigma^-$-$^5$He in the neutron excess of $(N-Z)/(N+Z)=$ 0.2 are also discussed.Comment: 35 pages, 11 figure

中間子ビームによる核内ΣN相互作用の研究

Tohoku University田村裕和課

Beam and SKS spectrometers at the K1.8 beam line

High-resolution spectrometers for both incident beams and scattered particles have been constructed at the K1.8 beam line of the Hadron Experimental Facility at J-PARC. A point-to-point optics is realized between the entrance and exit of QQDQQ magnets for the beam spectrometer. Fine-pitch wire chamber trackers and hodoscope counters are installed in the beam spectrometer to accept a high rate beam up to 107 Hz. The superconducting kaon spectrometer for scattered particles was transferred from KEK with modifications to the cryogenic system and detectors. A missing-mass resolution of 1.9 ± 0.1 MeV/c2 (FWHM) was achieved for the ∑ peaks of (π±, K+) reactions on a proton target in the first physics run of E19 in 2010