Inflection-point inflation in a hyper-charge oriented U(1)X model

Abstract

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 (φ I M P l ). In order for a renormalization group (RG) improved effective λφ 4 potential to develop an inflection-point, the running quartic coupling λ(φ) must exhibit a minimum with an almost vanishing value in its RG evolution, namely λ(φ I ) ≃ 0 and β λ (φ I ) ≃ 0, where β λ is the beta-function of the quartic coupling. In this paper, 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. Focusing on the case that the U(1) X gauge symmetry is mostly oriented towards the SM U(1) Y direction, we 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. In addition, the inflection-point inflation provides a unique prediction for the running of the spectral index α ≃ −2.7 × 10 −3 60 N 2 (N is the e-folding number), which can be tested in the near future.

Towards a measurement of the spectral runnings

“…−5 , as long as the potential does not experience a sudden change near CMB scales [10,[31][32][33][34][35][36]. In the same way that large local non-gaussianities would rule out single-field slow-roll inflation [37,38], a running α s much larger than ∼ 10 −3 would also imply a more complex model of inflation.…”

The waning of the WIMP? A review of models, searches, and constraints

“…The new Z particles, i.e., the gauge bosons of these U (1) groups, can be coupled to the SM fermions either indirectly, through kinetic mixing [242][243][244][245][246][247][248][249] with the Z -boson, or directly in case the SM fermions have non-trivial charges under the new symmetry group (see e.g., Refs. [250][251][252][253][254][255][256]). We will focus, in this section, on this last case while the case of kinetic mixing will be reviewed later in the text.…”

Nonminimal quartic inflation in classically conformal U(1)X extended standard model

“…Nevertheless, as has been pointed out in Ref. [27], the Z ′ boson with mass of O(1 TeV) can still be tested at the LHC Run-2 when the U(1) X gauge symmetry is oriented to the SM U(1) Y hyper-charge direction, namely, |x H | ≫ 1.…”