Effective Lagrangians and Light Gravitino Phenomenology
Abstract
We construct the low-energy effective lagrangian for supersymmetry breaking models with a light gravitino. Our effective lagrangian is written in terms of the spin-1/2 Goldstino (the longitudinal component of the gravitino) transforming under a non-linear realization of supersymmetry. The Goldstino is derivatively coupled. We use this lagrangian to place bounds on the supersymmetry breaking scale \sqrt{F} from Goldstino phenomenology. The most stringent bounds come from the coupling of a single photon to Goldstino pairs. For gauge-mediated models, this coupling arises at one loop in the effective lagrangian, and supernova cooling allows \sqrt{F} > 610 GeV or \sqrt{F} < 35 GeV for left-handed slepton masses of order 200 GeV. Nucleosynthesis gives a bound \sqrt{F} \gsim 190 GeV for \Delta N_\nu = 0.8. The invisible width of the Z$gives a bound \sqrt{F} > 140 GeV for tan\beta = 2.Keywords
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