Living orthogonally: quasi-universal extra dimensions

Abstract

The minimal Universal Extra Dimension scenario is highly constrained owing to opposing constraints from the observed relic density on the one hand, and the nonobservation of new states at the LHC on the other. Simple extensions in five-dimensions can only postpone the inevitable. Here, we propose a six-dimensional alternative with the key feature being that the SM quarks and leptons are localized on orthogonal directions whereas gauge bosons traverse the entire bulk. Several different realizations of electroweak symmetry breaking are possible, while maintaining agreement with low energy observables. This model is not only consistent with all the current constraints opposing the minimal Universal Extra Dimension scenario but also allows for a multi-TeV dark matter particle without the need for any fine-tuning. In addition, it promises a plethora of new signatures at the LHC and other future experiments.

Fat brane and seesaw mechanism in extra dimensions

“…The solutions of Eqs. (7) and (8) are found for the two different regions in the ED space, that is, inside the fat brane and outside it. The solution for the wave function in region I have the form f (n) 2 (y) = A n cos(x n y/R) + B n sin(x n y/R), but imposing that it vanishes at y = 0 in order to satisfy the coupled BC, we have the following solutions for this region…”

“…Extra dimensions (ED) have been used to explain a plethora of phenomena in particle physics and cosmology, including the hierarchy [1][2][3][4][5][6][7][8] and flavor problems [9][10][11], proton stability [12], the origin of electroweak symmetry breaking [13][14][15][16], the breaking of grand unified gauge groups [17][18][19][20], the number of fermion generations [21][22][23][24][25][26], the seesaw mechanism [27,28], and leptogenesis [29]. The standard model (SM) itself can be enlarged if its content is promoted to fields that propagate into a compact ED, in the so-called Universal Extra Dimension (UED) models.…”