Monophoton signals in light gravitino production at $e^+e^-$ colliders

Understand

We revisit the monophoton plus missing energy signature at $e^+e^-$ colliders in supersymmetric (SUSY) models where the gravitino is very light.

• There are two possible processes which provide the signal: gravitino pair production and associated gravitino production with a neutralino, leading the monophoton final state via an additional photon radiation and via the neutralino decay, respectively.
• By using the superspace formalism, we construct a model that allows us to study the parameter space for the both processes.
• We show that the signal cross section and the photon spectra provide information on the masses of the SUSY particles as well as the SUSY breaking scale.