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

TL;DR

This study investigates the $ ext{Sigma}$-nucleus potential for $ ext{Sigma}^-$-$^5$He using inclusive spectra from the $^6$Li($ ext{pi}^-$, $K^+$) reaction at 1.2 GeV/$c$, revealing a repulsive and absorptive potential consistent with heavier nuclei.

Contribution

It provides a phenomenological analysis of the $ ext{Sigma}$-nucleus potential for $ ext{Sigma}^-$-$^5$He, incorporating experimental data and a Woods-Saxon potential model, which is novel for this specific system.

Findings

The $ ext{Sigma}^-$-$^5$He potential is repulsive and absorptive.

Strengths of $V_ ext{Sigma} oughly +30$ MeV and $W_ ext{Sigma} oughly -26$ MeV fit the data.

Results are consistent with analyses for heavier nuclei.

Abstract

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.