Browsing by Subject "Higgs Physics"

Sort by: Order: Results:

Now showing items 1-5 of 5
  • Di Chiara, Stefano; Tuominen, Kimmo (2015)
    We study an extension of the Standard Model featuring a hidden sector that consists of a new scalar charged under a new SU(N)(D) gauge group, singlet under all Standard Model gauge interactions, and coupled with the Standard Model only via a Higgs portal. We assume that the theory is classically conformal, with electroweak symmetry breaking dynamically induced via the Coleman-Weinberg mechanism operating in the hidden sector. Due to the symmetry breaking pattern, the SU(N)(D) gauge group is completely Higgsed and the resulting massive vectors of the hidden sector constitute a stable dark matter candidate. We perform a thorough scan over the parameter space of the model at different values of N = 2, 3, and 4, and investigate the phenomenological constraints. We find that N = 2, 3 provide the most appealing model setting in light of present data from colliders and dark matter direct search experiments. We expect a heavy Higgs to be discovered at LHC by the end of Run II or the N = 3 model to be ruled out.
  • Cordero-Cid, A.; Hernandez-Sanchez, J.; Keus, V.; King, S. F.; Moretti, S.; Rojas, D.; Sokolowska, D. (2016)
    We study an extension of the Standard Model (SM) in which two copies of the SM scalar SU(2) doublet which do not acquire a Vacuum Expectation Value (VEV), and hence are inert, are added to the scalar sector. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z(2) symmetry. The lightest neutral particle from the inert sector, which has a mixed CP-charge due to CP-violation, is hence a Dark Matter (DM) candidate. We discuss the new regions of DM relic density opened up by CP-violation, and compare our results to the CP-conserving limit and the Inert Doublet Model (IDM). We constrain the parameter space of the CP-violating model using recent results from the Large Hadron Collider (LHC) and DM direct and indirect detection experiments.
  • Huitu, Katri; Keus, Venus; Koivunen, Niko; Lebedev, Oleg (2016)
    ATLAS and CMS have reported an excess in the flavor violating decay of the Higgs boson, h -> mu tau. We show that this result can be accommodated through a mixing of the Higgs with a flavon, the field responsible for generating the Yukawa matrices in the lepton sector. We employ a version of the Froggatt-Nielsen mechanism at the electroweak scale, with only the leptons and the flavon transforming non-trivially under the corresponding symmetry group. Non-observation of charged lepton flavor violation (LFV) in other processes imposes important constraints on the model, which we find to be satisfied in substantial regions of parameter space.
  • Keus, Venus; Koivunen, Niko; Tuominen, Kimmo (2018)
    We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Higgs doublet model (2HDM) and its extension by a singlet scalar. We focus on the contributions of the added scalars to the anomalous magnetic moment of the muon, (g - 2)(mu), in the presence of CP-violation, and the electric dipole moment of the electron (eEDM) in these models. In the absence of CP-violation, CP-even and CP-odd scalars contribute with an opposite sign to the anomalous magnetic moment of the muon and as a result these models generally require very light scalars to explain the observed discrepancy in (g - 2)(mu). We study the effect of CP-violation on the anomalous magnetic moment of the muon and its compatibility with the eEDM constraints. We show that given the current status of the global set of constraints applied on all values of cot beta, in the CP-violating scalar extensions, there exist no viable parameter space in agreement with both a(mu), and eEDM bounds.
  • Gorda, Tyler; Helset, Andreas; Niemi, Lauri; Tenkanen, Tuomas V. I.; Weir, David J. (2019)
    Due to the infrared problem of high-temperature field theory, a robust study of the electroweak phase transition (EWPT) requires use of non-perturbative methods. We apply the method of high-temperature dimensional reduction to the two Higgs doublet model (2HDM) to obtain three-dimensional effective theories that can be used for non-perturbative simulations. A detailed derivation of the mapping between the full four-dimensional and the effective three-dimensional theories is presented. The results will be used in future lattice studies of the 2HDM. In the limit of large mass mixing between the doublets, existing lattice results can be recycled. The results of such a study are presented in a companion paper.