A Novel String Derived Z' With Stable Proton, Light-Neutrinos and R-parity violation

Understand

The Standard Model indicates the realization of grand unified structures in nature, and can only be viewed as an effective theory below a higher energy cutoff.

• While the renormalizable Standard Model forbids proton decay mediating operators due to accidental global symmetries, many extensions of the Standard Model introduce such dimension four, five and six operators.
• Furthermore, quantum gravity effects are expected to induce proton instability, indicating that the higher energy cutoff scale must be above 10^{16}GeV.
• Quasi-realistic heterotic string models provide the arena to explore how perturbative quantum gravity affects the particle physics phenomenology.