Minimal nonsupersymmetricSO(10)model: Gauge coupling unification, proton decay, and fermion masses

Abstract

We present a minimal renormalizable non-supersymmetric SO(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54 H + 126 H + 10 H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 10 35 yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of τ p 1.29 × 10 34 yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, M I ≈ (10 13 − 10 14 ) GeV which is also the B − L scale, is of the right order for the righthanded neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p → e + π 0 and p → νπ + .Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario. *

Axion predictions in SO(10) × U(1)PQ models

“…1 In fact, it is well established that GUTs based on the gauge group SO(10) [17,18] may solve the fundamental problems i)-iv) discussed above exploiting the same mechanisms as our bottom-up variant of SMASH [19][20][21][22][23][24]. In fact, the right-handed neutrinos and thus the seesaw mechanism and the possibility of baryogenesis via thermal leptogenesis [25] occur automatically in these models.…”

“…a 45 H , also charged under the PQ symmetry [21,23]. A third way is to introduce an SO(10) singlet complex scalar field responsible for the U(1) PQ symmetry breaking [24]. We will consider in this paper benchmark models from all these three categories.…”

“…According to the latter, scalars get masses of the order of their VEVs, so that the scalars remaining active in the RG at a given scale are those whose VEVs lie below that scale. We consider however an exception [24,33]: in order to have a 2HDM at low energies, we will assume that Σ u and Σ d , the SM doublets in the (15, 2, 2) P S of the 126 H , have masses of the order of M BL . Such a choice is not arbitrary.…”

“…where 24) with f PQ andN k determined from the VEVs and PQ charges as in equations (3.18) and (3.21). As anticipated earlier, the θ k parameter for a given group (see (3.1)) and the axion enter the low-energy Lagrangian in the combination θ k + 1/f A,k A.…”

The ATLAS diboson resonance in non-supersymmetric SO(10)

“…Majorana mass terms of right-handed neutrinos can be generated at an intermediate scale, which may explain the smallness of neutrino masses. These interesting aspects have stimulated many extensive studies of SO(10) GUTs [15][16][17][18][19][20][21][22].…”