We consider numerical fits to non-supersymmetric SO(10)-based models in which neutrino mass is generated by the type-I or type-II seesaw mechanism or a combination of both.The fits are performed with a sophisticated top-down procedure, taking into account the renormalization group equations of the gauge and Yukawa couplings, integrating out relevant degrees of freedom at their corresponding mass scales, and using recent data for the Standard Model observables. We find acceptable fits for normal neutrino mass ordering only and with neutrino mass generated by either type-I seesaw only or a combination of types I and II seesaw in which type-I seesaw is dominant. Furthermore, we find predictions from the best fit regarding the small neutrino masses, the effective neutrinoless double beta decay mass, and the leptonic CP-violating phase. Finally, we show that the fits are rather insensitive to the chosen value of the unification scale. * tohlsson@kth.se † pernow@kth.se arXiv:1903.08241v2 [hep-ph] 19 Jun 2019 from M GUT to M Z , a complete analysis should integrate out the right-handed neutrinos at their respective mass scales, which has been carried out in Refs. [18,23]. Other works either performed the fits at M GUT or assumed that all right-handed neutrinos were integrated out simultaneously during the RG evolution.In this work, we consider fits to non-SUSY SO(10) models with neutrino mass being generated by either the type-I or type-II seesaw mechanism or a combination of both, similar to Ref. [25]. The procedure used is similar to that of Ref. [18], which involves sampling the parameters of the models at M GUT , evolving them down to M Z using the RGEs, and comparing the resulting values to data of the observables. The novelty of this work is the combination of the type-I and type-II seesaw mechanisms with a proper and complete treatment of the RG evolution, including integrating out right-handed neutrinos at their respective mass scales. Furthermore, we use updated data for all fermion observables. This paper is structured as follows. First, in Sec. II, we present the model that we investigate and the origin of the seesaw mechanism in SO(10). Next, in Sec. III, we describe how the parameters of this model are related to those of the SM. Then, in Sec. IV, we discuss the parametrization and the numerical procedure used. Finally, in Sec. V, we present the results before summarizing our findings and concluding in Sec. VI. II. MODELThe model that we consider is a non-SUSY SO(10) model with each generation of fermions and right-handed neutrinos belonging to a 16 F representation, whereas the Higgs scalars reside in the 10 H and 126 H representations. We also introduce a global U(1) PQ symmetry which has a double purpose. Firstly, it solves the strong CP problem and provides the QCD axions [26][27][28][29]. Secondly, and more importantly for the Yukawa sector, it allows us to complexify the real 10 H representation without introducing additional couplings [30], as described in Sec. II A.We assume that the SO(10) symmetr...

We investigate the complete renormalization group running of fermion observables in two different realistic non-supersymmetric models based on the gauge group SO(10) with intermediate symmetry breaking for both normal and inverted neutrino mass orderings. Contrary to results of previous works, we find that the model with the more minimal Yukawa sector of the Lagrangian fails to reproduce the measured values of observables at the electroweak scale, whereas the model with the more extended Yukawa sector can do so if the neutrino masses have normal ordering. The difficulty in finding acceptable fits to measured data is a result of the added complexity from the effect of an intermediate symmetry breaking as well as tension in the value of the leptonic mixing angle θ 23 .

We present a minimal non-supersymmetric SO(10) GUT breaking directly to the Standard Model gauge group. Precise gauge coupling unification is achieved due to the presence of two color-octet scalars, one of which is accessible to LHC searches. Proton lifetime is predicted to be below 4.5 × 10 34 years, which is within the projected five-year sensitivity of the proposed Hyper-Kamiokande experiment. We find that the Standard Model observables are reproduced to a reasonable accuracy in a numerical fit, which also predicts the unknown neutrino parameters. Finally, the two scalar representations stabilize the electroweak vacuum and the dark matter is comprised of axions.