Any long-lived particle with negative charge can be captured in the Coulomb field of an atomic nucleus thus forming a hydrogenlike exotic atom. The particle which initially may be trapped in a state with high principal quantum number n runs through its atomic cascade, primarily by emitting electrons of the host atom through the Auger effect, or by emitting atomic X-rays, depending on the transition energy between two successive atomic levels. One can estimate that this cascade takes between τ c = 10-15 and 10-19 seconds, depending on the nuclear charge number Z1. Therefore, the lifetime τ of the trapped particle must be long as compared to the cascade time τ c . As far as hadrons are concerned, these must be particles which are either stable or which decay via weak interactions. Some candidates are listed in Table 6.1.
KeywordsOptical Potential Partial Wave Amplitude Absorptive Part Exotic Atom Pionic Wave Function
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