Warped Unification, Proton Stability and Dark Matter

TL;DR

It is shown that solving the problem of baryon-number violation in nonsupersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza-Klein particle.

Abstract

Many extensions of the Standard Model have to face the problem of new unsuppressed baryon-number violating interactions. In supersymmetry, the simplest way to solve this problem is to assume R-parity conservation. As a result, the lightest supersymmetric particle becomes stable and a well-motivated dark matter candidate. In this paper, we show that solving the problem of baryon number violation in non supersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza-Klein particle. This exotic particle has gauge quantum numbers of a right-handed neutrino, but carries fractional baryon-number and is related to the top quark within the higher-dimensional GUT. A combination of baryon-number and SU(3) color ensures its stability. Its relic density can easily be of the right value for masses in the 10 GeV--few TeV range. An exciting aspect of these models is that the entire parameter space will be tested at near future dark matter direct detection experiments. Other exotic GUT partners of the top quark are also light and can be produced at high energy colliders with distinctive signatures.

Figures (4)

• Figure 1: Lightest mass of ($-+$) KK fermion as a function of its $c$-parameter. From bottom to top, $M_{KK}=$ 3, 5, 7, 10 TeV. $e^{k \pi r}\sim M_{Pl}/$TeV is the warp factor of RS geometry.
• Figure 2: Example of relic density predictions in warped $SO(10)$ for two values of $M_{KK}$. $c_{t_R}=-1/2$, $c_{t_L,b_L}=0.4$, all $c$'s for other fermions being larger than 1/2. Each region is obtained by varying both $g_{10}$ (from $g^{\prime}$ to $g_s$) and $c_{\nu^{\prime}_L} \in [c_{t_L}- 0.5 , c_{t_L}+ 0.5]$.
• Figure 3: Example (where the Higgs is a PGB) of predictions for elastic scattering cross sections between the LZP and a nucleon (independent of LZP mass). For each $M_{KK}$ region, the four lines denote different values of the $Z^0$-LZP coupling corresponding to, from top to bottom, $c_{\nu^{\prime}_L}=-0.1, 0.1,0.4,0.9$. Horizontal dotted line indicates present experimental limit, which only applies for some range of WIMP masses, see DMplotter for instance. For this range of LZP masses, only $g_{10}$ values below 0.55 survive in the $M_{KK}= 3$ TeV case.
• Figure 4: Pair production and decay of $b^{\prime}_L$, GUT partner of the LZP. Decay occurs through $X^{\prime}$--$X_s$ mixing due to bulk $SO(10)$ breaking.