Sneutrino Tribrid In ation in Supersymmetric GUTs

Abstract

We realize in ation in Supersymmetric GUT models through a scalar eld which acts as a in aton to connect the particle physics with in ation. Therefore, two models of tribrid in ation are constructed in which sneutrino plays the role of in aton. Both models contains right handed neutrino. However, right handed neutrino is gauge singlet in SU(5) and gauge non singlet in GSM U(1)B􀀀L. A realistic sneutrino tribrid in ation model is constructed in an R-symmetric SU(5) grand uni ed theory (GUT). To avoid the monopole problem, a pseudosmooth in ationary trajectory is generated with the help of an additional Z5 symmetry which is broken during and after in ation. The predictions of in ationary parameters are made at the central value of the scalar spectral index, ns = 0:968. The largest possible value of the tensor to scalar ratio, r . 0:0027, is obtained with subPlanckian eld values (. mP ). A successful realization of reheating and leptogenesis is achieved by avoiding the gravitino problem with a reheat temperature as low as 106 GeV. The predicted range of the gauge symmetry breaking scale, 5 1016 . M=GeV . 5 1017, turns out to be somewhat larger than the typical GUT scale. With additional vectorlike families, a successful gauge coupling uni cation is achieved by avoiding the no-go theorem related to R-symmetric SU(5) GUT. We present a successful realization of sneutrino tribrid in ation model based on a gauged U(1)B􀀀L extension of Minimal Supersymmetric Standard Model (MSSM). A single interaction term involving the B 􀀀 L Higgs eld and the right-handed neutrinos serves multiple purposes. These include the generation of heavy Majorana masses for the righthanded neutrinos to provide an explanation for the tiny neutrino masses via the seesaw mechanism, a realistic scenario for reheating and non-thermal leptogenesis with a reheat temperature as low as 106 GeV, and a successful realization of in ation with right-handed sneutrino as the in aton. The matter parity which helps avoid rapid proton decay survives as a Z2 subgroup of a U(1) R-symmetry. Depending on the choice of model parameters it yields the predicted range of the tensor to scalar ratio, 3 10􀀀11 . r . 7 10􀀀4 (6 10􀀀7 . r . 0:01), and the running of the scalar spectral index, 􀀀0:00022 . dns=d ln k . 􀀀0:0026 (􀀀0:00014 . dns=d ln k . 0:005), along with the B􀀀L breaking scale, 3 1014 . M=GeV . 5 1015 (6 1015 . M=GeV . 2 1016), calculated at the central value of the scalar spectral index, ns = 0:966, reported by Planck 2018. The possibility of realizing metastable cosmic strings in a grand uni ed theory setup is brie y discussed. The metastable cosmic string network admits string tension values in the range 10􀀀8 . G s . 10􀀀6, and predicts a stochastic gravitational wave background lying within the 2- bounds of the recent NANOGrav 12.5-yr data.