An E${}_6$ interpretation of an $e^{+}{e}^{-}\gamma \gamma E{/}_T$ event

Abstract

The lowest-dimensional representation of the group E${}_6$ contains both the standard quarks and leptons and a set of exotic quarks and leptons whose decays can involve a series of chains ending in radiative decay of one light neutrino species to another. An example is given based on the decomposition E${}_6\to$ SU(2)${}_I\times$ SU(6), where SU(2)${}_I$ is an ``inert'' subgroup whose gauge bosons $W_I^{(\pm )}$ and $Z_I$ are all electromagnetically neutral, while SU(6) contains the conventional SU(5) grand-unified group. The possibility is explored that such a chain is responsible for an event observed by the Collider Detector at Fermilab (CDF) involving the production in proton-antiproton collisions at $E_{c.m.}=1.8$ TeV of an electron-positron pair, two photons, and missing energy ($e^{+}{e}^{-}\gamma \gamma E{/}_T$).

Comments: 14 pages, latex, no figures. Revised version submitted to PRD