Single-photon events ine+e−collisions

We provide a detailed investigation of single-photon production processes in $e^{+}{e}^{-}$ collisions with missing momenta carried by neutrinos or neutralinos. The transition amplitudes for both processes can be organized into a generic simplified, factorized form; each neutral $V\pm A$ vector current of missing energy carriers is factorized out and all the characteristics of the reaction are solely included in the electron vector current. Firstly, we apply the generic form to give a unified description of single-photon production with a Dirac-type or Majorana-type neutrino pair and to confirm their identical characteristics as suggested by the so-called practical Dirac-Majorana confusion theorem. Secondly, we show that the generic amplitude form is maintained with the anomalous P- and C-invariant $\mathrm{WW}\gamma$ couplings in the neutrino-associated process and it enables us to easily understand the large contributions of the anomalous $\mathrm{WW}\gamma$ couplings at higher energies and, in particular, at points away from the Z-resonance peak. Finally, the neutralino-associated process, which receives modifications in both the left-handed and right-handed electron currents due to the exchanges of the left-handed and right-handed selectrons, can be differentiated from the neutrino-associated ones through the left-right asymmetries and/or the circular polarization of the outgoing photon.