Abstract
We consider a simple extension of the minimal left-right symmetric model (LRSM) in order to explain the PeV neutrino events seen at the IceCube experiment from a heavy decaying dark matter. The dark matter sector is composed of two fermions: one at PeV scale and the other at TeV scale such that the heavier one can decay into the lighter one and two neutrinos. The gauge annihilation cross sections of PeV dark matter are not large enough to generate its relic abundance within the observed limit. We include a pair of real scalar triplets ΩL,R which can bring the thermally overproduced PeV dark matter abundance into the observed range through late time decay and consequent entropy release thereby providing a consistent way to obtain the correct relic abundance without violating the unitarity bound on dark matter mass. Another scalar field, a bitriplet under left-right gauge group is added to assist the heavier dark matter decay. The presence of an approximate global U(1)X symmetry can naturally explain the origin of tiny couplings required for long-lived nature of these decaying particles. We also show, how such an extended LRSM can be incorporated within a non-supersymmetric SO(10) model where the gauge coupling unification at a very high scale naturally accommodate a PeV scale intermediate symmetry, required to explain the PeV events at IceCube.
Highlights
We consider a simple extension of the minimal left-right symmetric model (LRSM) in order to explain the PeV neutrino events seen at the IceCube experiment from a heavy decaying dark matter
While we do not follow a general top-down approach here similar to [44, 45], we start with a left-right symmetric model having necessary particle content to produce the correct dark matter relic abundance along with the IceCube high energy neutrino events and consider the possible embedding of these particles within SO(10) multiplets
The important stage of symmetry breaking G224 → GSM is happened when righthanded Higgs field ΩR(1, 3, 15) gets its non-zero vev. This symmetry breaking scale is fixed at few PeV scale such that decaying dark matter ΣR, right-handed charged gauge boson WR and relevant scalars playing an important role in dark matter phenomenology and IceCube explanation — all lie around that scale
Summary
The left-right symmetric model [39,40,41,42,43] is one of the most widely studied BSM framework that can simultaneously explain the origin of tiny neutrino masses and parity violation at weak interactions. The scalar content of the minimal LRSM consist of a bidoublet Φ responsible for generating Dirac mass terms of all fermions and for breaking the electroweak gauge symmetry spontaneously. The minimal model has a pair of complex triplet scalars ∆L,R in order to break the LRSM gauge symmetry spontaneously to that of the SM and to generate Majorana mass terms of light and heavy neutrinos. The parity odd scalar helps in gauge coupling unification as we will discuss later, and splits the masses of left and right handed dark matter candidates. A non-zero vev of the parity odd singlet scalar σ lead to the masses of fermion triplets as MR = MΣ + λσ σ , ML = MΣ − λσ σ This generates a mass splitting of 2λσ σ between the two dark matter particles. In LSkicnalar the covariant derivatives Dμ for the scalars can be written in a way similar to that of the fermions
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