Abstract:

Leptogenesis has become one of the leading theories to explain the baryon asymmetry of the universe. The existence of non-zero but tiny neutrino masses has been established through neutrino oscillation experiments. The smallness of the neutrino masses can be understood by introducing heavy right-handed neutrinos. If such neutrinos were produced in the early universe and decayed out of equilibrium, they could generate a finite lepton asymmetry, which would subsequently be converted into the observed baryon asymmetry. However, experimental verification of this theory has remained elusive. We point out that the decay of right-handed neutrinos produces a background of gravitational waves. Detecting this background would provide direct evidence for leptogenesis and the existence of heavy right-handed neutrinos. At the end of the talk, I will discuss the prospects for detecting this gravitational wave background.