EXPLORATORY STUDIES OF ANOMALOUSLY LONG-LIVED HADRONIC ATOMS

点击翻译按钮获取中文摘要

(1) Extensitive experimental programs on long-lived antiprotons in helium media have been carried out by using the antiproton beam from LEAR at CERN.First, delayd annihilation time spectra of antiprotons were measured precisely. Not only in liquid phase but also in gas and solid phase 3% of stopped antiprotons were observed to have lifetimes about 3-4 microseconds. Secondly, laser resonance spectroscopy was developed to clarify the mechanism of this anomalous longevity. The method proposed was to induce stimulated transitions between a metastable state and a short-lived state using an intense pulsed laser and to detect the transition as a sharp spike in delayd annihilation time spectra. Successful observations of many resonance transitions came out. The resonance wavelengths observed agree with theoretical expectations, which established that the metastability arises from long-lived states of large angular momenta. The precise spectroscopy including the observation of hyperfine structure has provided important data on the particle-antiparticle symmetry and few-body theories. Various effects of surrounding helium and foregn atoms and molecules on the metastable atoms have also been found and studied by laser spectroscopy.(2) Deeply-bound pionic states in 207Pb have been discocovered at GSI using the 208Pb (d, 3He) reaction at 600 MeV.