Combining Direct & Indirect Kaon CP Violation to Constrain the Warped KK Scale

TL;DR

This paper combines measurements of direct and indirect Kaon CP violation to set new lower bounds on the Warped KK scale, highlighting the impact of flavor constraints on extra-dimensional models.

Contribution

It demonstrates how incorporating epsilon'/epsilon_K constraints raises the lower bound on the KK scale in Randall-Sundrum models with a bulk Higgs.

Findings

Lower bound on KK scale is 5.5 TeV with a bulk Higgs.

Bound increases to 7.5 TeV in the two-site limit.

Analysis provides the flavor structure of the model with a bulk Higgs.

Abstract

The Randall-Sundrum (RS) framework has a built in protection against flavour violation, but still generically suffers from little CP problems. The most stringent bound on flavour violation is due to epsilon_K, which is inversely proportional to the fundamental Yukawa scale. Hence the RS epsilon_K problem can be ameliorated by effectively increasing the Yukawa scale with a bulk Higgs, as was recently observed in arXiv:0810.1016. We point out that incorporating the constraint from epsilon'/\epsilon_K, which is proportional to the Yukawa scale, raises the lower bound on the KK scale compared to previous analyses. The bound is conservatively estimated to be 5.5 TeV, choosing the most favorable Higgs profile, and 7.5 TeV in the two-site limit. Relaxing this bound might require some form of RS flavour alignment. As a by-product of our analysis, we also provide the leading order flavour structure of the theory with a bulk Higgs.