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Testing the Seesaw Mechanism and Leptogenesis with Gravitational Waves
Jeff A Dror1,2, Takashi Hiramatsu3, Kazunori Kohri4,5,6
1Department of Physics, University of California, Berkeley, California 94720, USA.
Physical Review Letters
|February 15, 2020
Summary
The seesaw mechanism and thermal leptogenesis could be tested using gravitational waves. Future space missions may detect cosmic string gravitational waves, probing the entire thermal leptogenesis range.
Area of Science:
- Particle Physics
- Cosmology
- Astrophysics
Background:
- Neutrino masses are explained by the seesaw mechanism, which requires right-handed neutrinos.
- Thermal leptogenesis, a mechanism for generating baryon asymmetry, is linked to the seesaw mechanism.
- Current models often place right-handed neutrinos at high energy scales, near grand unification.
Purpose of the Study:
- To explore the testability of the seesaw mechanism with thermal leptogenesis via stochastic gravitational backgrounds.
- To identify symmetries that allow for lighter right-handed neutrinos while maintaining consistency with neutrino data.
- To investigate the potential for detecting gravitational waves from cosmic strings generated by symmetry breaking.
Main Methods:
- Analyzing the implications of lighter right-handed neutrinos for the seesaw mechanism and thermal leptogenesis.
- Enumerating possible symmetries that protect light right-handed neutrinos and their breaking patterns.
- Calculating the expected stochastic gravitational wave background from cosmic strings associated with these symmetries.
Main Results:
- Lighter right-handed neutrinos, consistent with atmospheric and solar neutrino data, necessitate a symmetry protection mechanism.
- The breaking of such symmetries below the reheating temperature can lead to detectable gravitational waves from cosmic strings.
- Future space-borne gravitational wave missions have the potential to probe the entire parameter space relevant for thermal leptogenesis.
Conclusions:
- The seesaw mechanism with thermal leptogenesis is potentially testable through observations of the stochastic gravitational wave background.
- Cosmic string networks provide a viable source for detectable gravitational waves in scenarios with light right-handed neutrinos.
- Experimental verification of these gravitational waves would offer crucial insights into the origin of neutrino masses and matter-antimatter asymmetry.
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