Universal extra dimension: Violation of Kaluza-Klein parity

TL;DR

This paper explores how asymmetric interactions in the Universal Extra Dimension model violate KK parity, altering dark matter stability and collider signatures, thus impacting the model's testability at experiments like the LHC.

Contribution

It introduces and analyzes KK-parity violating interactions in UED, showing their effects on dark matter and collider phenomenology, which differ from the minimal UED scenario.

Findings

KK parity violation removes dark matter stability

It relaxes bounds on the compactification radius

Collider signals are significantly different from minimal UED

Abstract

The minimal Universal Extra Dimension (mUED) model respects the Kaluza-Klein (KK) parity $(-1)^n$, where $n$ is the KK number. However, it is possible to have interactions located at only one of the two fixed points of the $S_1/\ztwo$ orbifold. Such asymmetric interactions violate the KK parity. This kills the cold dark matter component of UED but also removes the upper bound on the inverse compactification radius, and thus non-observation of the KK excitations even at the Large Hadron Collider does not necessarily invalidate the model. Apart from the decay of the lightest $n=1$ KK excitation, this leads to collider signals which are markedly different from those in the mUED scenario. The phenomenological consequences of such KK-parity violating terms are explored.