Evidence for narrow resonant structures at $W approx 1.68$ and $W approx 1.72$ GeV in real Compton scattering off the proton

First measurement of the beam asymmetry $Sigma$ for Compton scattering off the proton in the energy range $E_{gamma}=0.85 - 1.25$ GeV is presented. The data reveals two narrow structures at $E_{gamma}= 1.036$ and $E_{gamma}=1.119$ GeV. They may signal narrow resonances with masses near $1.68$ and $1.72$ GeV, or they may be generated by the sub-threshold $KLambda$ and $omega p$ production. Their decisive identification requires additional theoretical and experimental efforts.