Fedor Bezrukov

The Standard Model Higgs boson as the inflaton

We argue that the Higgs boson of the Standard Model can lead to inflation and produce cosmological perturbations in accordance with observations. An essential requirement is the non-minimal coupling of the Higgs scalar field to gravity; no new particle besides already present in the electroweak theory is required.

Higgs boson mass and new physics

A bstractWe discuss the lower Higgs boson mass bounds which come from the absolute stability of the Standard Model (SM) vacuum and from the Higgs inflation, as well as the prediction of the Higgs boson mass coming from the asymptotic safety of the SM. We account for the three-loop renormalization group evolution of the couplings of the SM and for a part of the two-loop corrections that involve the QCD coupling αs to the initial conditions for their running. This is one step beyond the current state-of-the-art procedure (“one-loop matching-two-loop running”). This results in a reduction of the theoretical uncertainties in the Higgs boson mass bounds and predictions, associated with the SM physics, to 1–2xa0GeV. We find that with the account of existing experimental uncertainties in the mass of the top quark and αs (taken at the 2σ level) the bound reads MHu2009≥u2009Mmin (equality corresponds to the asymptotic-safety prediction), where

Higgs inflation: consistency and generalisations

{{M}_{{min }}}=left( {129pm 6} right)

On initial conditions for the Hot Big Bang

GeV. We argue that the discovery of the SM Higgs boson in this range would be in agreement with the hypothesis of the absence of new energy scales between the Fermi and Planck scales, whereas the coincidence of MH with Mmin would suggest that the electroweak scale is determined by Planck physics. In order to clarify the relation between the Fermi and Planck scales a construction of an electron-positron or muon collider with a center-of-mass energy ~ (200u2009+u2009200xa0GeV) (Higgs and t-quark factory) would be needed.

Standard Model Higgs boson mass from inflation: Two loop analysis

We analyse the self-consistency of inflation in the Standard Model, where the Higgs field has a large non-minimal coupling to gravity. We determine the domain of energies in which this model represents a valid effective field theory as a function of the background Higgs field. This domain is bounded above by the cutoff scale which is found to be higher than the relevant dynamical scales throughout the whole history of the Universe, including the inflationary epoch and reheating. We present a systematic scheme to take into account quantum loop corrections to the inflationary calculations within the framework of effective field theory. We discuss the additional assumptions that must be satisfied by the ultra-violet completion of the theory to allow connection between the parameters of the inflationary effective theory and those describing the low-energy physics relevant for the collider experiments. A class of generalisations of inflationary theories with similar properties is constructed.

A facility to search for hidden particles at the CERN SPS: the SHiP physics case.

We analyse the process of reheating the Universe in the electroweak theory where the Higgs field plays a role of the inflaton. We estimate the maximal temperature of the Universe and fix the initial conditions for radiation-dominated phase of the Universe expansion in the framework of the Standard Model (SM) and of the νMSM - the minimal extension of the SM by three right-handed singlet fermions. We show that the inflationary epoch is followed by a matter dominated stage related to the Higgs field oscillations. We investigate the energy transfer from Higgs-inflaton to the SM particles and show that the radiation dominated phase of the Universe expansion starts at temperature Tr (3-15) × 1013GeV, where the upper bound depends on the Higgs boson mass. We estimate the production rate of singlet fermions at preheating and find that their concentrations at T r are negligibly small. This suggests that the sterile neutrino Dark Matter (DM) production and baryogenesis in the νMSM with Higgs-driven inflation are low energy phenomena, having nothing to do with inflation. We study then a modification of the νMSM, adding to its Lagrangian higher dimensional operators suppressed by the Planck scale. The role of these operators in Higgs-driven inflation is clarified. We find that these operators do not contribute to the production of Warm Dark Matter (WDM) and to baryogenesis. We also demonstrate that the sterile neutrino with mass exceeding 100keV (a Cold Dark Matter (CDM) candidate) can be created during the reheating stage of the Universe in necessary amounts. We argue that the mass of DM sterile neutrino should not exceed few MeV in order not to overclose the Universe.

Standard Model Higgs boson mass from inflation

We extend the analysis of [1] of the Standard Model Higgs inflation accounting for two-loop radiative corrections to the effective potential. As was expected, higher loop effects result in some modification of the interval for allowed Higgs masses mmin < mH < mmax, which somewhat exceeds the region in which the Standard Model can be considered as a viable effective field theory all the way up to the Planck scale. The dependence of the index ns of scalar perturbations on the Higgs mass is computed in two different renormalization procedures, associated with the Einstein (I) and Jordan (II) frames. In the procedure I the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to ns = 0.97 and r = 0.0034 respectively. In the procedure II the index ns acquires the visible dependence on the Higgs mass and and goes out of the admitted interval at mH below mmin. We compare our findings with the results of [2].

keV sterile neutrino dark matter in gauge extensions of the standard model

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, [Formula: see text] and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the standard model and describe interactions between new particles and four different portals-scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the standard model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation.

Higgs inflation at the critical point

We analyse one-loop radiative corrections to the inflationa ry potential in the theory, where inflation is driven by the St andard Model Higgs field. We show that inflation is possible provided the Higgs mass mH lies in the interval mmin < mH < mmax, where mmin = [136.7 + (mt− 171.2)× 1.95] GeV, mmax = [184.5 + (mt− 171.2)× 0.5] GeV and mt is the mass of the top quark. In the renormalization scheme associated with the Einstein frame the predictions of the spectral index of scalar fluctuati ons and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to ns = 0.97 and r = 0.0034 correspondingly.

Light inflaton Hunter's Guide

It is known, that a keV scale sterile neutrino is a good warm dark matter candidate. We study how this possibility could be realized in the context of gauge extensions of the standard model. The naieve expectation leads to large thermal overproduction of sterile neutrinos in this setup. However, we find that it is possible to use out-of-equilibrium decay of the other right-handed neutrinos of the model to dilute the present density of the keV sterile neutrinos and achieve the observed dark matter density. We present the universal requirements that should be satisfied by the gauge extensions of the standard model, containing right-handed neutrinos, to be viable models of warm dark matter, and provide a simple example in the context of the left-right symmetric model.