  We calculate formation spectra of eta-nucleus systems in (pi,N) reactions
with nuclear targets, which can be performed at existing and/or forthcoming
facilities, including J-PARC, in order to investigate eta-nucleus interactions.
Based on the N^*(1535) dominance in the eta N system, eta-mesic nuclei are
suitable systems for study of in-medium properties of the N^*(1535) baryon
resonance, such as reduction of the mass difference of N and N^* in nuclear
medium, which affects level structure of the eta and N^*-hole modes. We find
that clear information on the in-medium N^*- and eta-nucleus interactions can
be obtained through the formation spectra of the eta-mesic nuclei. We also
discuss the experimental feasibilities by showing several spectra of (pi,N)
reactions calculated with possible experimental settings. Coincident
measurements of pi N pairs from the N^* decays in nuclei help us to reduce
backgrounds.
