Radiative neutralino production in low energy supersymmetric models. II. The case of beam polarization

Abstract

We study the production of the lightest neutralinos in the radiative process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}\ensuremath{\gamma}$ in low energy supersymmetric models for the International Linear Collider energies with longitudinally polarized electron and positron beams. For this purpose we consider the case of nonminimal supersymmetric standard model as well as the case of minimal supersymmetric standard model. At the first stage of a linear collider, with $\sqrt{s}=500\text{ }\text{ }\mathrm{GeV}$, the radiative production of the lightest neutralinos may be a viable channel to study supersymmetric partners of the standard model particles, especially if the other supersymmetric particles are too heavy to be pair produced. We consider in detail the effect of beam polarization on the production cross section. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the nonminimal and minimal supersymmetric standard model when the electron and positron beams are longitudinally polarized. In order to assess the feasibility of experimentally observing the radiative neutralino production process, we consider the background to this process coming from the standard model process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}$ with longitudinally polarized electron and positron beams. We also consider the supersymmetric background to the radiative neutralino production process coming from the radiative production of the scalar partners of the neutrinos (sneutrinos) ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\stackrel{\texttildelow{}}{\ensuremath{\nu}}{\stackrel{\texttildelow{}}{\ensuremath{\nu}}}^{*}\ensuremath{\gamma}$, with longitudinally polarized beams. This process can be a background to the radiative neutralino production when the sneutrinos decay invisibly.