Exploration of decaying dark matter in a left-right symmetric model

TL;DR

This paper investigates how decaying dark matter within a left-right symmetric model can produce observable cosmic-ray signals, especially in neutrinos and gamma-rays, by involving triplet scalars that decay into leptons.

Contribution

It introduces a model where dark matter decay is mediated by triplet scalars with lepton number, enhancing neutrino signals and explaining cosmic-ray observations.

Findings

Neutrino flux can be significantly enhanced due to triplet couplings.

Predicted muon flux from neutrinos can be several times larger than direct decay models.

High energy gamma-ray contributions depend on mass hierarchy between DM and triplets.

Abstract

$SU(2)_L$ triplet scalars appear in models motivated for the left-right symmetry, neutrino masses and dark matter (DM), etc.. If the triplets are the main decay products of the DM particle, and carry nonzero lepton numbers, they may decay dominantly into lepton pairs, which can naturally explain the current experimental results reported by PAMELA and Fermi-LAT or ATIC. We discuss this possibility in an extended left-right symmetric model in which the decay of DM particle is induced by tiny soft charge-conjugation ($C$) violating interactions, and calculate the spectra for cosmic-ray positrons, neutrinos and gamma-rays. We show that the DM signals in the flux of high energy neutrinos can be significantly enhanced, as the triplets couple to both charged leptons and neutrinos with the same strength. In this scenario, the predicted neutrino-induced muon flux can be several times larger than the case in which DM particle only directly decays into charged leptons. In addition, the charged components of the triplet may give an extra contribution to the high energy gamma-rays through internal bremsstrahlung process, which depends on the mass hierarchy between the DM particle and the triplet scalars.