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

We comment on the statement by Kuznetsov et al. that the structure around $W=1.72$ GeV seen in the beam asymmetry in Compton scattering off the proton is not observed in the total cross section of $\eta$ photoproduction on the neutron.

Figure 1

Excitation functions for quasifree photoproduction of $\eta$ mesons. Inset: total cross sections for quasifree neutrons bound in the deuteron (red circles) and in ${}^3\mathrm{He}$ nuclei (green squares). Data are as published in Fig. 1 of Ref. [5]. Fit curves include Breit-Wigner resonance for the structure at 1726 MeV. Main figure: finer binned data for the measurement with deuterium target. Red circles (blue triangles): quasifree neutron (proton) data. Curves: total fit (solid black curve), background contributions (dashed black curve), and sum of two narrow signal Breit-Wigner functions (red solid curve). Open black circles: background-subtracted neutron data. Vertical lines: markers at $W=1681$ MeV and $W=1726$ MeV.