After nearly 10 years since the existence of deeply-bound (1s and 2p) pionic states was theoretically predicted, we have finally succeeded to observe those states using the recoilless (d, He-3) reactions on lead targets. The observed strong-interaction shifts and widths can set stringent constraints on the s-wave part, of the pion-nucleus optical potential parameters, which in turn can be used to estimate the 'effective pion mass' in the nucleus. Possibilities to extend this method of recoilless production of meson-nucleus bound states to study the in-medium behavior of other mesons, such as eta and omega are also discussed. [References: 33]
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