Speaker
Description
Inflection-point inflation is an interesting possibility to realize a successful slow-roll inflation when inflation is driven by a single scalar field with its value during inflation below the Planck mass ($\phi_I \leq M_{Pl}$). In order for a renormalization group (RG) improved effective $\lambda \phi^4$ potential to develop an inflection-point, the running quartic coupling $\lambda(\phi)$ must exhibit a minimum with an almost vanishing value in its RG evolution, namely $\lambda(\phi_I) \simeq 0$ and $\beta_{\lambda}(\phi_I) \simeq 0$, where $\beta_{\lambda}$ is the beta-function of the quartic coupling. We consider the inflection-point inflation in the context of the minimal U(1)$_X$ extended Standard Model (SM), a generalization of the minimal U(1)$_{B-L}$ model,where the U(1)$_X$ symmetry is realized as a linear combination of the SM U(1)$_Y$ and the U(1)$_{B-L}$ gauge symmetries.We identify the U(1)$_X$ Higgs field with the inflaton field. For a successful inflection-point inflation to be consistent with the current cosmological observations, the mass ratios among the U(1)$_X$ gauge boson, the right-handed neutrinos, and the U(1)$_X$ Higgs boson are fixed. We first consider the $B-L$ limit with the gauge boson mass less than $1$ TeV. We find that the scenario can be tested in the future collider experiments such as the High-Luminosity LHC and the SHiP experiments. On the other extreme, we consider the scenario such that the U(1)$_X$ gauge symmetry is mostly oriented towards the SM U(1)$_Y$ direction and investigate a consistency between the inflationary predictions and the latest LHC Run-2 results on the search for a narrow resonance with the di-lepton final state.
Summary
Inflation
