Sneutrino tribrid inflation, metastable cosmic strings and gravitational waves

Abstract

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.

Leptogenesis triggered by a first-order phase transition

“…Thus, we briefly comment on the possible signals. In our scenario, there are two sources of the GWs: first, the U(1) B−L FOPT itself generates GWs via vacuum bubble collision, sound waves and magneto-hydrodynamics (MHD) turbulence in the plasma [52][53][54][55][56][57]; second, the cosmic strings forming after the U(1) B−L breaking keep emitting GWs during the evolution of the Universe [82][83][84][85][86][87][88].…”

Probing Miracle-less WIMP Dark Matter via Gravitational Waves Spectral Shapes

“…Numerical simulations [38,39] based on Nambu-Goto action indicate that dominant energy loss from a string loop is in the form of GW radiation if the underlying symmetry is gauged. The resulting GW background is detectable when the symmetry breaking scale Λ CS 10 9 GeV-a fact that makes CS an outstanding probe of super-high scale physics [40][41][42][43][44][45][46][47]. This includes the present scenario of Miracle-less WIMP featuring a high-scale (Λ CS ≡ v BL ) breaking of a gauged U (1) B−L .…”

Probing superheavy dark matter with gravitational waves

“…The BPs obtained in the last section are for M ν R 10 9 GeV, much higher than the available energy scale of any traditional DM direct, indirect or collider searches, making it almost hopeless to test superheavy DM scenario. However, the recently developed GW astronomy offers an unique opportunity to probe this scenario: as the RHN mass M ν R is associated with a high-scale U(1) B−L breaking, which forms cosmic strings that can generate detectable stochastic GW signals [56][57][58][59][60][61][62].…”