Entropy, Baryon Asymmetry and Dark Matter from Heavy Neutrino Decays

TL;DR

This paper explores how decays of heavy Majorana neutrinos can explain the early universe's entropy, baryon asymmetry, and dark matter production, linking neutrino properties with superparticle masses.

Contribution

It demonstrates a natural mechanism connecting heavy neutrino decays to entropy, baryogenesis, and dark matter, with quantitative constraints on superparticle and neutrino masses.

Findings

Heavy neutrino decays can produce the observed baryon asymmetry.

Thermal gravitino production accounts for dark matter.

Neutrino mass measurements can test the viability of this scenario.

Abstract

The origin of the hot phase of the early universe remains so far an unsolved puzzle. A viable option is entropy production through the decays of heavy Majorana neutrinos whose lifetimes determine the initial temperature. We show that baryogenesis and the production of dark matter are natural by-products of this mechanism. As is well known, the cosmological baryon asymmetry can be accounted for by leptogenesis for characteristic neutrino mass parameters. We find that thermal gravitino production then automatically yields the observed amount of dark matter, for the gravitino as the lightest superparticle and typical gluino masses. As an example, we consider the production of heavy Majorana neutrinos in the course of tachyonic preheating associated with spontaneous B-L breaking. A quantitative analysis leads to contraints on the superparticle masses in terms of neutrino masses: For a light neutrino mass of 10^{-5} eV the gravitino mass can be as small as 200 MeV, whereas a lower neutrino mass bound of 0.01 eV implies a lower bound of 9 GeV on the gravitino mass. The measurement of a light neutrino mass of 0.1 eV would rule out heavy neutrino decays as the origin of entropy, visible and dark matter.