Standard coupling unification in SO(10), hybrid seesaw neutrino mass and leptogenesis, dark matter, and proton lifetime predictions

Abstract

We discuss gauge coupling unification of SU(3) C × SU(2) L × U(1) Y descending directly from non-supersymmetric SO(10) while providing solutions to the three outstanding problems of the standard model: neutrino masses, dark matter, and the baryon asymmetry of the universe. Conservation of matter parity as gauged discrete symmetry for the stability and identification of dark matter in the model calls for high-scale spontaneous symmetry breaking through 126 H Higgs representation. This naturally leads to the hybrid seesaw formula for neutrino masses mediated by heavy scalar triplet and right-handed neutrinos. Being quadratic in the Majorana coupling, the seesaw formula predicts two distinct patterns of right-handed neutrino masses, one hierarchical and another not so hierarchical (or compact), when fitted with the neutrino oscillation data. Predictions of the baryon asymmetry via leptogenesis are investigated through the decays of both the patterns of RHν masses. A complete flavor analysis has been carried out to compute CP-asymmetries including washouts and solutions to Boltzmann equations have been utilised to predict the baryon asymmetry. The additional contribution to vertex correction mediated by the heavy left-handed triplet scalar is noted to contribute as dominantly as other Feynman diagrams. We have found successful predictions of the baryon asymmetry for both the patterns of right-handed neutrino masses. The SU(2) L triplet fermionic dark matter at the TeV scale carrying even matter parity is naturally embedded into the non-standard fermionic representation 45 F of SO(10). In addition to the triplet scalar and the triplet fermion, the model needs a nonstandard color octet fermion of mass ∼ 5 × 10 7 GeV to achieve precision gauge coupling unification at the GUT mass scale M 0 U = 10 15.56 GeV.Open Access, c The Authors. Article funded by SCOAP 3 .doi:10.1007/JHEP04(2017)075 JHEP04(2017)075Threshold corrections due to superheavy components of 126 H and other representations are estimated and found to be substantial. It is noted that the proton life time predicted by the model is accessible to the ongoing and planned experiments over a wide range of parameter space.

Unification, proton decay, and topological defects in non-SUSY GUTs with thresholds

“…The neutrino and charged fermion mass and mixing generation in the context of unified theories are discussed in [24,[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. In [62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] different cosmological aspects and dark matter scenarios are discussed. An important result of the present paper, using the goodness of fit test for unification with two-loop renormalisation group evolution equations (RGEs), is the extent to which the inclusion of threshold corrections significantly affects the proton lifetime, allowing several scenarios, which would otherwise be excluded, to survive.…”

Matter parity violating dark matter decay in minimal SO(10), unification, vacuum stability and verifiable proton decay

“…Such a direct SO(10) breaking model is prominently well established in SUSY GUTs [74,75] and also has been applied in non-SUSY SO(10) [26,30,50,76]. In the context of protecting non-SUSY grand desert models by GUT threshold effects , particularly those due to superheavy gauge bosons, such a direct breaking model of SO (10) has been also used earlier [77,78]…”

“…Remnants of gauged discrete symmetries [46][47][48] such as R-parity in SUSY and matter parity in non-SUSY theories have played crucial roles in determining stability and phenomenology of dark matter [23][24][25][26][28][29][30]. In general if a higher rank gauge theory containing U (1) B−L as one of its subgroups leads to SM gauge theory SU (2) L × U (1) Y × SU (3) C ≡ G 213 , then matter parity (MP) of the SM is conserved as a gauged discrete symmetry…”

“…Application of matter parity conserving non-SUSY SO (10) has been extensively exploited [23][24][25][26]28,30] to predict fermions or scalars as WIMP DM candidates [53,54]. Gravity induced small violation of R-parity as the corresponding DM stabilising gauged discrete symmetry in SUSY theories has been extensively investigated to predict new interesting physical phenomena [29].…”

High Scale Type-II Seesaw, Dominant Double Beta Decay within Cosmological Bound and LFV Decays in SU(‎5)

“…All the generational mixings have been found to be much larger than the corresponding quark mixings. Theoretically [6][7][8][9][10][11][12][13] neutrino masses are predicted through various seesaw mechanisms [14][15][16][17][18][19][20][21][22][23][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. In a minimal left-right symmetric [44][45][46][47] grand unified theory (GUT) like SO(10) [48,49] where parity (P) violation in weak interaction is explained along with fermion masses [50][51][52][53][54][55], a number of these seesa...…”