About estimations of a one-photon background in neutrino-oscillation experiments at low neutrino energies

The possible sources of one-photon radiation as a background for the quasi-elastic reaction ν _μ + n → μ⁻ + p are considered. They are relevant in experiments on determination of oscillation parameters at low neutrino energies (E _ν ∼ 1 GeV). The estimation for the cross section of the reaction ν _μ + n → μ ⁻ + p + γ is given at E _ν ^lab = 0.7 GeV as 0.65% of the corresponding cross section of quasielastic reaction. The mechanisms of quasi-elastic reaction are also considered at low neutrino energies on a quark level. The text was submitted by the authors in English.