Abstract
SO(10) grand unified theories can ensure the stability of new particles in terms of the gauge group structure itself, and in this respect are well suited to accommodate dark matter (DM) candidates in the form of new stable massive particles. We introduce new fermions in two vector 10 representations. When SO(10) is broken to the standard model by a minimal 45 + 126 + 10 scalar sector with $SU(3)_C \otimes SU(2)_L \otimes SU(2)_R\otimes U(1)_{B-L}$ as intermediate symmetry group, the resulting lightest new states are two Dirac fermions corresponding to combinations of the neutral members of the $SU(2)_L$ doublets in the 10's, which get splitted in mass by loop corrections involving $W_R$. The resulting lighter mass eigenstate is stable, and has only non-diagonal $Z_{L,R}$ neutral current couplings to the heavier neutral state. Direct detection searches are evaded if the mass splitting is sufficiently large to suppress kinematically inelastic light-to-heavy scatterings. By requiring that this condition is satisfied, we obtain the upper limit $M_{W_R} \lesssim 25$ TeV.
Highlights
A plethora of astrophysical and cosmological observations have firmly established that non-baryonic dark matter (DM) must exist in our Universe, and contribute to the overall cosmological energy density about five times more than ordinary matter
Breaking the SO(10) grand unified theories (GUTs) group to the standard model (SM) via the intermediate group SU (3)C ⊗SU (2)L⊗SU (2)R⊗U (1)B−L by means of vacuum expectation values in 45H ⊕126H ⊕10H preserves an exact discrete gauge symmetry Z2, which ensures the stability of the lightest among new fermions belonging to 10-dimensional vector representations
We have added to the SO(10) model two fermionic 10’s, and we have argued that the lightest stable states belonging to these representations correspond to the four neutral members of the SU (2)L ⊗ SU (2)R bi-doublets contained in the two 10’s
Summary
A plethora of astrophysical and cosmological observations have firmly established that non-baryonic dark matter (DM) must exist in our Universe, and contribute to the overall cosmological energy density about five times more than ordinary matter. None of the particles of the standard model (SM) can account for the DM, which constitutes a clear hint of new physics. Electrically neutral and weakly interacting massive particles with mass in the GeV-TeV range are ubiquitous in new physics models, and appear to be well suited to reproduce quantitatively the measured DM energy density if their stability on cosmological time scales can be ensured. From the model-building point of view, DM stability is most commonly enforced by assuming some suitable symmetry that forbids its decay into lighter SM particles.
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