How many new particles do we need after the Higgs boson?

TL;DR

This paper discusses the minimal extension of the Standard Model with right-handed neutrinos, exploring how many new particles are needed to address neutrino oscillations, dark matter, and baryon asymmetry.

Contribution

It analyzes the potential of adding right-handed neutrinos to complete the Standard Model and explains their role in solving cosmological puzzles.

Findings

Right-handed neutrinos can explain neutrino oscillations.

Minimal extension may address dark matter and baryon asymmetry.

Further particles or mechanisms might be necessary for a complete theory.

Abstract

The discovery of the scalar boson completes the experimental confirmation of the particles predicted by the Standard Model, which achieves to describe almost all phenomena observed in nature in terms of a few symmetry principles and a handful of numbers, the constants of nature. Neutrino oscillations are the only confirmed piece of evidence for physics beyond the Standard Model found in the laboratory. They can easily be explained if the neutrinos have partners with right handed chirality like all other fermions. Remarkably, right handed neutrinos can simultaneously explain long standing puzzles from cosmology, namely Dark Matter and the baryon asymmetry of the universe. I discuss how close this minimal extension of the Standard Model by right handed neutrinos can bring us to a complete theory of nature and what else may be needed.