Photoproduction of eta mesons off protons for 0.75 GeV<E(gamma)<3 GeV

Phys Rev Lett. 2005 Jan 14;94(1):012004. doi: 10.1103/PhysRevLett.94.012004. Epub 2005 Jan 14.

Abstract

Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.