Small steps towards Grand Unification and the electron/positron excesses in cosmic-ray experiments

TL;DR

This paper proposes a minimal extension to the standard model adding Majorana fermions that achieve gauge coupling unification, provide a dark matter candidate, and explain cosmic-ray electron/positron excesses through fermion decay.

Contribution

It introduces a simple model extension with specific fermions that unify gauge couplings, account for dark matter, and explain cosmic-ray anomalies.

Findings

Gauge coupling unification at >10^{15} GeV with fermion mass constraints.

A symmetry ensures the neutral fermion component's long lifetime.

Decay of the fermion explains cosmic-ray electron/positron excesses.

Abstract

We consider a small extension of the standard model by adding two Majorana fermions; those are adjoint representations of the SU(2)_L and SU(3)_c gauge groups of the standard model. In this extension, the gauge coupling unification at an energy scale higher than 10^{15} GeV is realized when the masses of the triplet and the octet fermions are smaller than 10^4 GeV and 10^{12} GeV, respectively. We also show that an appropriate symmetry ensures a long lifetime of the neutral component of the triplet fermion whose thermal relic density naturally explains the observed dark matter density. The electron/positron excesses observed in recent cosmic-ray experiments can be also explained by the decay of the triplet fermion.