Minimal universal extra dimensions (mUED) is often thought to predict that the lightest Kaluza-Klein particle (LKP) is the Kaluza-Klein gauge boson $B^1$, leading to conventional missing energy signals at colliders and weakly interacting massive particle (WIMP) dark matter. In fact, the implications of mUED are far richer: the $B^1$, charged Higgs boson $H^{\pm 1}$, and graviton $G^1$ are all possible LKPs, leading to many different phases with distinct signatures. Considering the complete phase diagram, we find predictions for charged or neutral particles with decay lengths of microns to tens of meters; WIMP, superWIMP, or charged relic particles; metastable particles with lifetimes of the order of or in excess of the age of the Universe; and scenarios combining two or more of these phenomena. In the cosmologically preferred region, the Higgs boson mass is between 180 and 245 GeV, the LKP mass is between 810 and 1400 GeV, and the maximal splitting between first Kaluza-Klein modes is less than 320 GeV. This region predicts a variety of exotic collider signals, such as slow charged particles, displaced vertices, tracks with nonvanishing impact parameters, track kinks, and even vanishing charged tracks, all of which provide early discovery possibilities at the Large Hadron Collider.

• Received 21 December 2006

DOI:https://doi.org/10.1103/PhysRevD.75.036004