A STANDARD-LIKE MODEL IN THE 4-DIMENSIONAL FREE FERMIONIC STRING FORMULATION

We show how the Standard Model may be derived from the heterotic string with no intermediate energy scale by using the free fermionic formulation. An explicit model is presented, with the following properties: (i) The observable gauge group is SU(3)C × SU(2)L × U(1)n where n = 1 or 2, after a possible symmetry breaking at the string level. (ii) The complete massless spectrum is derived and is shown to be anomaly free apart from a single "anomalous" U(1). In the observable sector there are only three generations of chiral fermions with their superpartners. (iii) There are enough scalar doublets and singlets to break the gauge symmetry in a realistic way. (iv) All trilinear superpotential couplings have been calculated. (v) The weak hypercharge is uniquely defined, including a possible new, generation independent, U(1) symmetry, which may remain unbroken down to low energies, and prevents fast proton decay. © 1990.