New measurements of the beam normal single spin asymmetry in the electron elastic and quasielastic scattering on the proton and deuteron, respectively, at large backward angles and at $⟨Q^2⟩=0.22(\mathrm{GeV}/c{)}^2$ and $⟨Q^2⟩=0.35(\mathrm{GeV}/c{)}^2$ are reported. The experimentally observed asymmetries are compared with the theoretical calculation of Pasquini and Vanderhaeghen [Phys. Rev. C 70, 045206 (2004).]. The agreement of the measurements with the theoretical calculations shows a dominance of the inelastic intermediate excited states of the nucleon, $\pi N$ and the $\mathrm{\Delta }$ resonance. The measurements explore a new, important parameter region of the exchanged virtual photon virtualities.

• Received 14 December 2016

DOI:https://doi.org/10.1103/PhysRevLett.119.012501