Observing Left-Right Symmetry in the Cosmic Microwave Background

Abstract

We consider the possibility of probing left-right symmetric model (LRSM) via cosmic microwave background (CMB). We adopt the minimal LRSM with Higgs doublets, also known as the doublet left-right model (DLRM), where all fermions including the neutrinos acquire masses only via their couplings to the Higgs bidoublet. Due to the Dirac nature of light neutrinos, there exist additional relativistic degrees of freedom which can thermalise in the early universe by virtue of their gauge interactions corresponding to the right sector. We constrain the model from Planck 2018 bound on the effective relativistic degrees of freedom and also estimate the prospects for planned CMB Stage IV experiments to constrain the model further. We find that $W_R$ boson mass below 4.06 TeV can be ruled out from Planck 2018 bound at $2\sigma$ CL in the exact left-right symmetric limit which is equally competitive as the LHC bounds from dijet resonance searches. On the other hand Planck 2018 bound at $1\sigma$ CL can rule out a much larger parameter space out of reach of present direct search experiments, even in the presence of additional relativistic degrees of freedom around the TeV corner. We also study the consequence of these constraints on dark matter in DLRM by considering a right handed real fermion quintuplet to be the dominant dark matter component in the universe.

29 pages, 8 figures, matches version accepted for publication in Phys. Rev. D

References in corpus (13)

• A direct empirical proof of the existence of dark matter
• CMB-S4 Science Case, Reference Design, and Project Plan
• Relic neutrino decoupling with flavour oscillations revisited
• SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope
• General CP Violation in Minimal Left-Right Symmetric Model and Constraints on the Right-Handed Scale
• Pathways to Naturally Small Dirac Neutrino Masses
• Dirac neutrinos and $N_{\mathrm{eff}}$
• Radiative Left-Right Dirac Neutrino Mass
• Naturally Stable Right-Handed Neutrino Dark Matter
• Type III Seesaw and Left-Right Symmetry
• Light Sterile Neutrino and Dark Matter in Left-Right Symmetric Models Without Higgs Bidoublet
• Observable Lepton Number Violation with Predominantly Dirac Nature of Active Neutrinos
• Dirac dark matter in $U(1{)}_{B-L}$ with Stueckelberg mechanism

Cited by in corpus (1)

• Dirac neutrinos and $N_{\mathrm{eff}}$ II: the freeze-in case