We present a successful realization of sneutrino tribrid inflation 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 field and the right-handed neutrinos serves multiple purposes. These include the generation of heavy Majorana masses for the right-handed 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 inflation with right-handed sneutrino as the inflaton. 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 yields the following 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 ≲ dn_s/dln k ≲ -0.0026 (-0.00014 ≲ dn_s/dln 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, n_s =0.966, reported by Planck 2018. The possibility of realizing metastable cosmic strings in a grand unified theory setup is briefly discussed. The metastable cosmic string network admits string tension values in the range 10-8≲ Gμs ≲ 10-6, and predicts a stochastic gravitational wave background lying within the 2-σ bounds of the recent NANOGrav 12.5-yr data.

A realistic tribrid model of sneutrino inflation is constructed in an R-symmetric SU (5) grand unified theory (GUT). To avoid the monopole problem, a pseudosmooth inflationary trajectory is generated with the help of an additional Z 5 symmetry which is broken during and after inflation. The predictions of inflationary parameters are made at the central value of the scalar spectral index, n s = 0.968. The largest possible value of the tensor to scalar ratio, r 0.0027, is obtained with sub-Planckian field values ( m P ). A successful realization of reheating and leptogenesis is achieved by avoiding the gravitino problem with a reheat temperature as low as 10 6 GeV. The predicted range of the gauge symmetry breaking scale, 5×10 16 M/GeV 5×10 17 , turns out to be somewhat larger than the typical GUT scale. With additional vectorlike families, a successful gauge coupling unification is achieved by avoiding the no-go theorem related to R-symmetric SU (5) GUT.

A supersymmetric hybrid inflation framework is employed to realize a class of non-minimal inflation models with U (1) R × Z n global symmetry. This framework naturally incorporates models based on grand unified theories by avoiding the most commonly faced monopole problem. The predictions of inflationary observables, the scalar spectral index n s = 0.960 − 0.966 and the tensor to scalar ratio r = 0.0031 − 0.0045, are in perfect agreement with the Planck 2018 data. For sub-Planckian values of the field the Z n symmetry is only allowed for n ≤ 4.