Universal extra dimension: Violation of Kaluza-Klein parity

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 $S_1\mathrm{/}\text{ztwo}$ 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.