Experimental consequences of no-scale supergravity in light of the CDF $ee\gamma\gamma$ event

Abstract

We explore two possible interpretations for the CDF $ee\gamma\gamma+E_T\hskip-13pt/\quad$ event in the context of a recently proposed one-parameter no-scale supergravity model with a light gravitino. We delineate the region in parameter space consistent with the kinematics of the event interpreted either as selectron pair-production ($p\bar p\to\tilde e^+\tilde e^-\,X$, $\tilde e=\tilde e_R,\tilde e_L$) or as chargino pair-production ($p\bar p\to\chi^+_1\chi^-_1\,X$). In the context of this model, the selectron interpretation requires $\tilde e=\tilde e_R$ and predicts comparable rates for $\ell^\pm\gamma\gamma+E_T\hskip-13pt/\quad$, whereas the chargino interpretation predicts comparable rates for $(\ell^\pm\ell^{'+}\ell^{'-},\ell^+\ell^-,\ell^+\ell^-jj)\,\gamma\gamma +E_T\hskip-13pt/\quad$. We also consider the constraints from LEP~1.5 and the expectations for LEP~2. We point out that one of the acoplanar photon pairs observed by the OPAL collaboration at LEP~1.5 may be attributable to supersymmetry in the present model via $e^+e^-\to\chi^0_1\chi^0_1\to \gamma\gamma+E_T\hskip-13pt/\quad$. We also show how similar future events at LEP~2 may be used to deduce the neutralino mass.