Extra matter at low energy

Abstract

Assuming that the Standard Model arises from the $E_8\times E_8$ Heterotic Superstring, we try to solve the discrepancy between the unification scale predicted by this theory ($\approx g_{GUT}\times 5.27\cdot 10^{17}$ GeV) and the value deduced from LEP experiments ($\approx 2\cdot 10^{16}$ GeV). This will allow us to predict the presence at low energies of three generations of supersymmetric Higgses and vector-like colour triplets.

Comments: Talk given at 1st International Conference on String Phenomenology, Oxford, 6-11 July 2002. 6 pages, 1 figure