Quintessence Saves Higgs Instability

We study a model where quintessence potential $e^{-\xi\phi}$ coupled to Higgs potential. We calculate the evolution of the quintessence, and track the running of the effective Higgs self-coupling. We find it slightly larger than that of the standard model in the past. Requiring the electroweak vacuum to be absolutely stable in inflationary era, we find a lower bound $\xi> 0.35\pm 0.05$, where the uncertainty is mainly from the measurement of the top quark mass. This lower bound, together with the upper bound from the observation for dark energy $\xi\lesssim0.6$, narrows down the parameter space and makes it possible to test this model in the near future. Interestingly, the bound on $\xi$, if actually shown to be the case by observation, supports the recently proposed Swampland Conjecture.Comment: 6 pages, 1 figur

LHC Search for Right-handed Neutrinos in Z′Z^\prime Models

We consider right-handed neutrino pair production in generic $Z^\prime$ models. We propose a new, model-independent analysis using final states containing a pair of same-sign muons. A key aspect of this analysis is the reconstruction of the RH neutrino mass, which leads to a significantly improved sensitivity. Within the $U(1)_{(B-L)_{3}}$ model, we find that at the HL-LHC it will be possible to probe RH neutrino masses in the range $0.2\lesssim M_{N_R} \lesssim 1.1\,$TeV.Comment: 6 pages, 5 figure