Z'-portal right-handed neutrino dark matter in the minimal non-exotic U(1) extension of the Standard Model

Dr. Nobuchika Okada (host Dev), University of Alabama
September 21, 2017 at 3:00 pm
241 Compton
Event Description 

I will discuss a concise dark matter (DM) scenario in the context of non-exotic U(1) extension of the Standard Model (SM), where a new U(1)_X gauge symmetry is introduced along with three generations of right-handed neutrinos (RHNs) and an SM gauge singlet Higgs field. The model is a generalization of the minimal gauged U(1)BL (baryon number minus lepton number) extension of the SM, in which the extra U(1)_X gauge symmetry is expressed as a linear combination of the SM U(1)_Y and U(1)_BL gauge symmetries. We introduce a Z_2-parity and assign an odd-parity only for one RHN among all particles, so that this Z_2-odd RHN plays a role of DM. The so-called minimal seesaw mechanism is implemented in this model with only two Z_2-even RHNs. In this context, we investigate physics of the RHN DM, focusing on the case that this DM particle communicates with the SM particles through the U(1)_X gauge boson (Z' boson). This "Z'-portal RHN DM" scenario is controlled by only three free parameters: the U(1)_X gauge coupling, the Z' boson mass (mZ'), and the U(1)_X charge of the SM Higgs doublet (x_H). We consider various phenomenological constraints to identify a phenomenologically viable parameter space. The most important constraints are the observed DM relic abundance and the LHC Run-2 results on the search for a narrow resonance with the di-lepton final state. We find that these are complementary with each other and narrow the allowed parameter region, leading to the lower mass bound of mZ'> 2.7 TeV. I will also discuss an update by the ATLAS collaboration (April, 2017) on the search for the narrow resonance.

Coffee: 2:30 pm, 241 Compton