Gauge coupling unification and light exotica in string theory.

Area of Science:

• High-energy particle physics
• String theory and cosmology
• Particle phenomenology

Background:

• The Standard Model of particle physics has limitations, motivating searches for new physics beyond it.
• String theory offers a framework for unifying gravity with other fundamental forces, potentially predicting new particles.
• Gauge coupling unification suggests that the strengths of fundamental forces converge at high energies.

Purpose of the Study:

• To investigate the implications of light vectorlike exotica with fractional electric charge for the CERN Large Hadron Collider (LHC).
• To explore the theoretical origins of such exotic particles within string theory constructions.
• To assess the consistency of these exotica with gauge coupling unification at the one-loop level.

Main Methods:

• Analysis of orbifold constructions within heterotic string theory to identify potential exotic states.
• One-loop calculations to examine the impact of these exotic particles on gauge coupling unification.
• Phenomenological considerations for detecting fractional-charged exotica at the LHC.

Main Results:

• Light vectorlike exotica with fractional electric charge are predicted by specific orbifold constructions of the heterotic string.
• These predicted exotica are compatible with gauge coupling unification at the one-loop level.
• The consistency holds even though these states do not form complete SU(5) multiplets.

Conclusions:

• The study provides a theoretical basis for the existence of fractional-charged exotic particles within string theory.
• These findings suggest potential new avenues for discovery at the CERN Large Hadron Collider.
• The results offer insights into the unification of fundamental forces and the structure of beyond-Standard-Model physics.