Seesaw neutrinos from the heterotic string

Area of Science:

• Particle Physics
• String Theory
• Cosmology

Background:

• The neutrino seesaw mechanism explains the small masses of neutrinos.
• Grand Unified Theories (GUTs) often incorporate seesaw mechanisms but require large representations.
• Heterotic string theory offers a framework for unifying fundamental forces and particles.

Purpose of the Study:

• To investigate the realization of the neutrino seesaw mechanism in E(8) x E(8) heterotic string theory.
• To analyze Z6 orbifold compactifications for their potential to host the seesaw mechanism.
• To determine if these models naturally generate the required Dirac Yukawa couplings and Majorana mass terms.

Main Methods:

• Studying E(8) x E(8) heterotic string theory compactifications on Z6 orbifolds.
• Analyzing the resulting gauge group and matter content for supersymmetry.
• Identifying the presence of Dirac Yukawa couplings and Majorana mass terms for neutrinos.

Main Results:

• Z6 orbifold compactifications yield the supersymmetric standard model gauge group and matter content.
• These models inherently possess the necessary ingredients for the neutrino seesaw mechanism.
• Large Majorana mass terms and Dirac Yukawa couplings are naturally present.
• No large GUT representations are required, unlike conventional seesaw models.
• The number of right-handed neutrinos can be substantial, up to O(100).

Conclusions:

• The neutrino seesaw mechanism is readily achievable in E(8) x E(8) heterotic string theory via Z6 orbifold compactifications.
• These string theory models offer a compelling alternative to traditional GUT-based seesaw mechanisms.
• The abundance of right-handed neutrinos in these models warrants further investigation into their cosmological implications.