Photoproduction of η-mesic ³He
/ Authors
M. Pfeiffer, J. Ahrens, J. Annand, R. Beck, G. Caselotti, S. Cherepnya, K. Fohl, L. Fog, D. Hornidge, S. Janssen
and 16 more authors
V. Kashevarov, R. Kondratiev, M. Kotulla, B. Krusche, J. Mcgeorge, I. MacGregor, K. Mengel, J. Messchendorp, V. Metag, R. Novotný, M. Rost, S. Sack, R. Sanderson, S. Schadmand, A. Thomas, D. Watts
/ Abstract
The photoproduction of eta-mesic He-3 has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma(3)He-<etaX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonancelike structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasibound state. This is supported by studies of a competing decay channel of such a quasibound eta-mesic nucleus into pi(0)pX. A binding energy of (-4.4+/-4.2) MeV and a width of (25.6+/-6.1) MeV is deduced for the quasibound eta-mesic state in He-3.
Journal: Physical Review Letters