The Quest for Pionic and Kaonic Nuclear Bound Systems Following Yukawa and Tomonaga

TL;DR

This paper reviews historical and recent developments in meson-nucleus bound states, emphasizing experimental evidence for chiral symmetry restoration and proposing a molecular structure for K- pp with a super strong nuclear force.

Contribution

It introduces new insights into pion and kaon interactions in nuclear media, highlighting experimental findings and theoretical models for dense nuclear systems involving Kbar mesons.

Findings

Experimental evidence for partial chiral symmetry restoration.

Proposal of K- pp as a molecular system with quasi-Lambda(1405).

Introduction of super strong nuclear force via migrating Kbar mesons.

Abstract

After sketching some historical events related to Yukawa and Tomonaga concerning the birth of mesons, the author describes recent developments in the spectroscopy of pion-nucleus bound states via "pion-transfer" reactions. The role of pions as Nambu-Goldstone bosons in nuclear media is emphasized by recently obtained experimental evidence for the partial restoration of chiral symmetry breaking. New light is shed on Kbar mesons, which play a unique role in forming dense nuclear systems. The basic unit, K- pp, is predicted to possess a molecular structure with quasi-Lambda(1405) as an "atomic constituent". We find here "super strong nuclear force" produced by a migrating real Kbar meson in the Heitler-London-Heisenberg scheme in place of the normal nuclear force mediated by Yukawa's virtual mesons.