The Reactions $\pi^{-}p \to \eta n$ and $\pi^{-}p \to X^{0}n$ at 15 and 40 GeV/c

Data on pi /sup -/p charge exchange interactions giving a recoil neutron and a forward-produced state which decays in a final state containing only gamma rays ( pi /sup 0/ to 2 gamma , eta to 2 gamma , omega to pi /sup 0/ gamma , X/sup 0/ to 2 gamma , pi /sup 0/ pi /sup 0 /, etc) are being collected at the Serpukhov accelerator at incident pi /sup -/ momenta between 15 and about 40 GeV/c by a IHEP-CERN (Karlsruhe-Pisa-Vienna) group. Preliminary results are reported for the differential cross section of the reactions pi /sup -/p to eta n and pi /sup -/p to X/sup 0/n up to t approximately=2 (GeV/c)/sup 2/ for eta and t approximately=1 (GeV/c)/sup 2/ for X/sup 0/. (0 refs).