A. Aydemir et al., The ratios of energy losses through photoneutrino process in superstring inspired E-6 model and in the standard model, MOD PHY L A, 16(8), 2001, pp. 497-505
In general E-6 inspired model which has two additional U(1) symmetries at t
he string scale whose one combination is a light enough vector boson Z(thet
a), we compute the contribution of Z(theta) to the gammae(-) --> e(-)<(<nu>
)over bar>nu scattering at the aim of calculating the energy loss. We find
that the two U(1)'s must be combined at 90 degrees to have a significant co
ntribution.