OBSERVABLES IN LOW-ENERGY SUPERSTRING MODELS

TLDR

Mixing with the single additional neutral gauge boson reduces the mass of the conventional Z⁰, constraining field vacuum expectation values by the experimental upper bound on this shift. The study compiles phenomenological constraints on the minimal low‑energy effective theory obtainable from the superstring via Calabi‑Yau compactification. The authors derive model‑dependent limits by imposing naturalness—requiring observables to be insensitive to input parameters—on the compiled constraints. Requiring a positive sneutrino mass squared constrains the supersymmetry‑breaking scale more tightly than lower bounds on new charged particles, and the analysis prefers the second neutral gauge boson to weigh ≲320 GeV, with dynamical gauge‑hierarchy generation possible if mt ≲70 GeV.

Abstract

We compile phenomenological constraints on the minimal low-energy effective theory which can be obtained from the superstring by Calabi-Yau compactification. Mixing with the single additional neutral gauge boson in this model reduces the mass of the conventional Z 0 , Field vacuum expectation values are constrained by the experimental upper bound on this shift. Then, requiring the sneutrino mass squared to be positive constrains the scale of supersymmetry breaking more than do lower bounds on the masses of new charged particles and of sparticles. More model-dependent constraints follow from the “naturalness” requirement that observables do not depend sensitively on input parameters. We find a preference for the second neutral gauge boson to weigh ≲320 GeV, [Formula: see text] GeV and [Formula: see text] GeV. Dynamical generation of the gauge hierarchy is possible if m t ≲70 GeV, with lower values of m t being favoured.