A SUPERSTRING Z' AT O(1 TeV)?

Abstract

We discuss the scale and effects of a new neutral gauge boson, Z', in our recently derived superstring standard-like model, which is a combination of B - L and T3R and provides a mechanism to suppress proton decay. We show that the mass and mixing angle of the Z' with the standard model Z depend only on MZ and MW. For the central values of MZ and MW from recent experiments, MZ'~1000 GeV . We discuss the effect of Z-Z' mixing on the width of the Z and investigate the effect on primordial nucleosynthesis calculations, from which we find that the existence of light right-handed neutrinos with a Z' is excluded unless MZ'≥1.5 TeV .

Moduli fixing in realistic string vacua

“…The left-moving {y, ω} states are divided into {y 3,···,6 }, {y 1 , y 2 , ω 5 , ω 6 }, {ω 1,···,4 } and χ 12 , χ 34 , χ 56 generate the left-moving N = 2 world-sheet supersymmetry. At the level of the NAHE set the sectors b 1 , b 2 and b 3 produce 48 multiplets, 16 from each, in the 16 representation of SO (10). The states from the sectors b j are singlets of the hidden E 8 gauge group and transform under the horizontal SO(6) j (j = 1, 2, 3) symmetries.…”

“…These additional vectors reduce the number of generations to three, one from each of the sectors b 1 , b 2 and b 3 , and simultaneously break the four dimensional gauge group. The assignment of boundary conditions to {ψ 1,···,5 } breaks SO (10) to one of its subgroups [11]. Similarly, the hidden E 8 symmetry is broken to one of its subgroups, and the flavor SO(6) 3 symmetries are broken to U(1) n , with 3 ≤ n ≤ 9.…”

“…(2.7), is to separate the gauge degrees of freedom, spanned by the world-sheet fermions {ψ 1,···,5 ,η 1 ,η 2 ,η 3 ,φ 1,···,8 }, from the internal compactified degrees of freedom {y, ω|ȳ,ω} 1,···,6 . In the realistic free fermionic models [11,14] this is achieved by the vector 2γ [14], with 10) which breaks the E 8 × E 8 symmetry to SO(16) × SO (16). The Z 2 × Z 2 twist induced by b 1 and b 2 breaks the gauge symmetry to SO(4) 3 × SO(10) × U(1) 3 × SO (16).…”

“…together with a consistent choice of one-loop GSO phases [9]. Both models produce three generations and the SO(10) GUT gauge group is broken to SU(3) × SU(2) × U(1) 2 .…”

“…A particular class of string compactifications that exhibit promising phenomenological properties are the so-called free fermionic heterotic-string models [4,5,6,7,8,9,10,11,12,13]. These models are related to Z 2 × Z 2 orbifold compactifications [14], and many of their appealing phenomenological properties are rooted in the underlying Z 2 × Z 2 orbifold structure [14].…”