Mass and Γ3π0/Γγγ decay branching ratio of the η-meson from the p(γ, η)p reaction

Abstract

Neat threshold photoproduction of eta-mesons from the proton has been measured at, the MAMI accelerator with the TAPS spectrometer. The mass of the eta-meson was deduced from the threshold energy for eta-photoproduction. The result of m(eta)=(547.12 +/- 0.06 +/- 0.25) MeV supports the low value of the eta-mass reported from a dp -< He-3(eta) measurement at SATURNE in 1992. The eta-decay branching ratio Gamma(3 pi degrees)/Gamma(gamma gamma) was measured to be (0.832 +/-0.005 +/-0.012)