Threshold effects on prediction for proton decay in non-supersymmetric E6 GUT with intermediate trinification symmetry

We consider a non-supersymmetric E6 Grand Unified Theory (GUT) with intermediate trinification symmetry SU(3)C×SU(3)L×SU(3)R×D (D denoted as D-parity for discrete left-right symmetry) and study the effect of one-loop threshold corrections arising due to every class of superheavy particles (scalars, fermions and vectors). It is observed that, the intermediate mass scale MI and sin2⁡θW remain unaffected by GUT threshold contributions. The threshold modified unification mass scale MU is in excellent agreement with the present experimental proton decay constraint. The novel feature of the model is that GUT threshold uncertainty of MU is found to be controlled by superheavy scalars only, leading to a very predictive scenario for proton decay, which can be verifiable within the foreseeable experiments.