Quest for a phenomenologically consistent low cutoff theory

The Randall-Sundrum model with the Higgs localized on the IR brane solves the gauge hierarchy problem. However, the associated low cutoff ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi mathvariant="normal">Λ</a:mi> <a:mo>∼</a:mo> <a:mn>10</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>TeV</a:mi> </a:mrow> </a:math> ) generically leads to unacceptably rapid nucleon decay and excessively large Majorana neutrino masses. Achieving consistency while simultaneously explaining the Yukawa hierarchy requires either a horizontal symmetry or a discrete gauged symmetry. We demonstrate that eliminating all dangerous operators within a horizontal symmetry framework must come with large and unattractive charge assignments, if possible at all. Hence, we consider an exact discrete gauged <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:msub> <d:mi mathvariant="bold">Z</d:mi> <d:mi>N</d:mi> </d:msub> </d:math> symmetry, with fermion mass hierarchies generated via wave function overlap. We employ this to reproduce the current Cabibbo-Kobayashi-Maskawa and Pontecorvo-Maki-Nakagawa-Sakata structures. Assuming universal five-dimensional Yukawa couplings, generation-blind profile for right-handed neutrinos, and flat profile for the third generation SM doublets, it predicts Dirac neutrinos with a total mass <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mo>∼</g:mo> <g:mn>66</g:mn> <g:mtext> </g:mtext> <g:mtext> </g:mtext> <g:mi>meV</g:mi> </g:math> . Since the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:msub> <i:mi mathvariant="bold">Z</i:mi> <i:mi>N</i:mi> </i:msub> </i:math> charges must be generation blind, flavor observables serve as key probes.