We analyze the prospects for discovering supersymmetry at the Fermilab Tevatron and CERN LEP colliders in the scenario that the lightest supersymmetric particle is a gravitino of mass < ∼ 1 keV. We consider in particular the case that the lightest neutralino has a nearly 100% branching fraction into gravitino + photon within the detector. This implies that supersymmetric events should contain both missing (transverse) energy and two energetic photons. Therefore one can search for supersymmetry simply through inclusive production of superpartners. We consider the exclusion and reach capabilities of the Tevatron in exploring the supersymmetric parameter space, and study the efficiencies which can be achieved in this search. We also consider the discovery reach and backgrounds at LEP with √ s = 160, 175, and 190 GeV. * Supported mainly by an INFN postdoctoral fellowship, Italy.

We have analyzed the single eeγγ + / E T event at CDF and found that the expected rate and kinematics are consistent with selectron pair production. We consider two classes of general low-energy supersymmetric theories, where either the lightest neutralino ("neutralino LSP" scenario) or the gravitino ("light gravitino" scenario) is the lightest supersymmetric particle. The parameter space of the supersymmetric Lagrangian is tightly constrained by the kinematics of the event and the branching ratios for the necessary decay chain of the selectron. We identify a region of the parameter space satisfying all low-energy constraints, and consistent with the selectron interpretation of the eeγγ + / E T event. We discuss other supersymmetric processes at Fermilab Tevatron and at CERN LEP in both scenarios that could confirm or exclude a supersymmetric explanation of the event, and that could distinguish between the neutralino LSP and the light gravitino scenarios. * Supported by a INFN postdoctoral fellowship, Italy.

We consider a general class of models with gauge-mediated supersymmetry breaking in which the gravitino is the lightest supersymmetric particle. Several qualitatively different scenarios arise for the phenomenology of such models, depending on which superpartner͑s͒ decay dominantly to the gravitino. At CERN LEP 2, neutralino pair production and slepton pair production can lead to a variety of promising discovery signals, which we systematically study. We investigate the impact of backgrounds for these signals and show how they can be reduced, and outline the effects of model parameter variations on the discovery potential. ͓S0556-2821͑97͒02815-4͔PACS number͑s͒: 14.80.Ly, 12.60.Jv to 1/F 2 ͒ in the light gravitino ͑small F͒ limit ͓24͔.In the GMSB models to be considered in this study, the NLSP is always either a neutralino or a charged slepton. In the former case, the lightest neutralino (Ñ 1 ) decays into a photon and a gravitino with a width ⌫͑Ñ 1 →␥G ͒ϭ 1␥ 48 m Ñ 1 5 M 2 m G 2 ϭ20 1␥ ͩ m Ñ 1 100 GeV ͪ 5 ͩ ͱF 10 TeV ͪ Ϫ4 eV,

A bstractW e report a study on the m easurem ent of the SU SY breaki ng scal e p F i n the fram ework of gauge-m edi ated supersym m etry breaki ng (G M SB ) m odel s at the LH C .T he work i s focused on the G M SB scenari o w here a stau i s the next-to-l i ghtest SU SY parti cl e (N LSP) and decays i nto a gravi ti no w i th l i feti m e c N LSP i n the range 0. 5 m to 1 km . W e study the i denti cati on ofl ongl i ved sl eptons usi ng the m om entum and ti m e of i ght m easurem ents i n the m uon cham bers of the AT LA S experi m ent. A real i sti c eval uati on ofthe stati sti caland system ati c uncertai nti es on the m easurem entofthe sl epton m assand l i feti m e i sperform ed,based on a detai l ed si m ul ati on of the detectorresponse.A ccessi bl e range and preci si on on p F achi evabl e w i th a counti ng m ethod are assessed. M any features ofouranal ysi s can be extended to the study ofdi erenttheoreti cal fram eworks w i th si m i l ar si gnatures at the LH C .

We present a refined and expanded analysis of the CDF eeγγ + / E T event as superpartner production, assuming the lightest neutralino is the lightest supersymmetric particle. A general low-energy Lagrangian is constrained by a minimum cross section times branching ratio into two electrons and two photons, kinematics consistent with the event, and LEP1-LEP130 data. We examine how the supersymmetric parameters depend on the kinematics, branching ratios and experimental predictions with a selectron interpretation of the event, and discuss to what extent these are modified by other interpretations. Predictions for imminent CERN LEP upgrades and the present and future Fermilab Tevatron are presented. Finally, we briefly discuss the possible connection to other phenomena including a light stop, the neutralino relic density, the shift in R b and the associated shift in α s , and implications for the form of the theory. * Supported mainly by a INFN postdoctoral fellowship, Italy.