Cosmic Coincidence and Asymmetric Dark Matter in a Stueckelberg Extension

Abstract

We discuss the possibility of cogenesis generating the ratio of baryon asymmetry to dark matter in a Stueckelberg U(1) extension of the standard model and of the minimal supersymmetric standard model. For the U(1) we choose $L_{\mu}-L_{\tau}$ which is anomaly free and can be gauged. The dark matter candidate arising from this extension is a singlet of the standard model gauge group but is charged under $L_{\mu}-L_{\tau}$. Solutions to the Boltzmann equations for relics in the presence of asymmetric dark matter are discussed. It is shown that the ratio of the baryon asymmetry to dark matter consistent with the current WMAP data, i.e., the cosmic coincidence, can be successfully explained in this model with the depletion of the symmetric component of dark matter from resonant annihilation via the Stueckelberg gauge boson. For the extended MSSM model it is shown that one has a two component dark matter picture with asymmetric dark matter being the dominant component and the neutralino being the subdominant component (i.e., with relic density a small fraction of the WMAP cold dark matter value). Remarkably, the subdominant component can be detected in direct detection experiments such as SuperCDMS and XENON-100. Further, it is shown that the class of Stueckelberg models with a gauged $L_{\mu}-L_{\tau}$ will produce a dramatic signature at a muon collider with the $\sigma(\mu^+\mu^-\to \mu^+\mu^-,\tau^+\tau^-)$ showing a detectable $Z'$ resonance while $\sigma(\mu^+\mu^-\to e^+e^-)$ is devoid of this resonance. Asymmetric dark matter arising from a $U(1)_{B-L}$ Stueckelberg extension is also briefly discussed. Finally, in the models we propose the asymmetric dark matter does not oscillate and there is no danger of it being washed out from oscillations.Comment: 36 pages, 7 figure