Measurement of Excitation Spectra in the 12C(p, d) Reaction near the eta ' Emission Threshold

Excitation spectra of C-11 are measured in the C-12(p, d) reaction near the eta' emission threshold. A proton beam extracted from the synchrotron SIS-18 at GSI with an incident energy of 2.5 GeV impinges on a carbon target. The momenta of deuterons emitted at 0 degrees are precisely measured with the fragment separator (FRS) operated as a spectrometer. In contrast to theoretical predictions on the possible existence of deeply bound eta'-mesic states in carbon nuclei, no distinct structures are observed associated with the formation of bound states. The spectra are analyzed to set stringent constraints on the formation cross section and on the hitherto barely known eta'-nucleus interaction.