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A value for the mass of the eta meson has been determined at the COSY-ANKEfacility through the measurement of a set of deuteron laboratory beam momentaand associated 3He center-of-mass momenta in the d+p -> 3He+X reaction. The etawas then identified by the missing-mass peak and the production thresholddetermined. The individual beam momenta were fixed with a relative precision of3 x 10^-5 for values around 3 GeV/c by using a polarized deuteron beam andinducing an artificial depolarizing spin resonance, which occurs at awell-defined frequency. The final-state momenta in the two-body d+p -> 3He+etareaction were investigated in detail by studying the size of the 3He momentumellipse with the forward detection system of the ANKE spectrometer. Finalalignment of the spectrometer for this high precision experiment was achievedthrough a comprehensive study of the 3He final-state momenta as a function ofthe center-of-mass angles, taking advantage of the full geometrical acceptance.The value obtained for the mass, m(eta)=(547.873 +- 0.005(stat) +- 0.027(syst))MeV/c^2, is consistent and competitive with other recent measurements, in whichthe meson was detected through its decay products.

New determination of the mass of the eta meson at COSY-ANKE