Search

We investigate the compatibility of pure gravity mediation (or minimal split supersymmetry) with chaotic inflation models in supergravity. We find that an approximate Z2 parity of the inflaton is useful to suppress gravitino production from the thermal bath and to obtain consistent inflation dynamics. We discuss the production of the lightest supersymmetric particle through the decay of the inflaton with approximate Z2 symmetry, and we find that a large gravitino mass is favored in order to avoid overproduction of the lightest supersymmetric particle, while a lower gravitino mass requires the tuning of parameters. This may explain why a gravitino mass of 0(100) TeV rather than 0(100) GeV may be natural [ABSTRACT FROM AUTHOR]

We estimate dark matter (DM) density for the Universe with a reheating temperature smaller than the mass of DM, assuming DM to be a weakly interacting massive particle. During the reheating process, an inflaton decays and releases high-energy particles, which are scattered inelastically by the thermal plasma and emit many particles. DMs are produced through these inelastic scattering processes and pair creation processes by high-energy particles. We properly take account of the Landau-Pomeranchuk-Migdal effect on inelastic processes and show that the resultant energy density of DM is much larger than that estimated in the literature and can be consistent with that observed when the mass of DM is larger than O( 100) GeV. [ABSTRACT FROM AUTHOR]

The axion solution to the strong CP problem calls for an explanation as to why the Lagrangian should be invariant under the global Peccei-Quinn (PQ) symmetry, U(1)PQ, to such a high degree of accuracy. In this paper, we point out that the U(1)PQ can indeed survive as an accidental symmetry in the low-energy effective theory, if the standard model gauge group is supplemented by a gauged and discrete R symmetry, ZRN, forbidding all dangerous operators that explicitly break the Peccei-Quinn symmetry. In contrast to similar approaches, the requirement that the ZRN symmetry be anomaly-free forces us, in general, to extend the supersymmetric standard model by new matter multiplets. Surprisingly, we find a large landscape of viable scenarios that all individually fulfill the current experimental constraints on the QCD vacuum angle as well as on the axion decay constant. In particular, choosing the number of additional multiplets appropriately, the order N of the ZRN symmetry can take any integer value larger than 2. This has interesting consequences with respect to possible solutions of the μ problem, collider searches for vectorlike quarks and axion dark matter. [ABSTRACT FROM AUTHOR]

We propose a curvaton model in which the initial condition of the curvaton oscillation is determined by its attractor behavior during inflation. Assuming a chaotic inflation model, we find that the initial condition determined by the attractor behavior is appropriate to generate a sizable non-Gaussianity contribution to the curvature perturbation, which will be tested in the foreseeable future. Implications on the thermal history of the Universe and on particle physics models are also discussed. [ABSTRACT FROM AUTHOR]

Vector-like quarks are introduced in various new physics models beyond the standard model (SM) at the TeV scale. We especially consider the case that the quark is singlet (triplet) under the SU(2)L (SU(3)c) gauge group and couples only to the third-generation quarks of the SM. The vector-like quark of this kind is often called a top partner. The top partner tp decays into bW, tZ, and th. In the ATLAS and CMS Collaborations, the top partner has been searched in the final states of bW and tZ, while the search based on the decay mode tp → th has not been started yet. However, the decay into th is important, since it is significantly enhanced if some strong dynamics exists in the TeV scale. In the presence of a light Higgs boson, the decay mode tp → th followed by h → bb produces three bottom quarks. We study the sensitivity for the top partner using multi-b-jet events at the 8 TeV run of the Large Hadron Collider (LHC) experiment. The multi-b-jet events turn out to play a complementary role to the existing tp --* bW and tZ searches by the ATLAS and CMS Collaborations. [ABSTRACT FROM AUTHOR]

We discuss the seesaw mechanism which includes the minimum number of parameters for successful leptogenesis and three neutrino oscillations in the spirit of Occam's razor. We show that models with two right-handed neutrinos with two texture zeros supported by Occam's razor cannot fit the observed neutrino parameters consistently for the normal light neutrino mass hierarchy. For the inverted light neutrino mass hierarchy, on the other hand, we find that the models can fit the observed neutrino parameters consistently. Besides, we show that the model predicts the maximal Dirac CP-phase of the neutrino mixing matrix in the measurable range in the foreseeable future for the inverted neutrino mass hierarchy. We also show that the predicted effective Majorana neutrino mass responsible for the neutrinoless double beta decay is around 50 meV which is also within reach of future experiments. [ABSTRACT FROM AUTHOR]

Vector bosons heavier than 10-22 eV can be viable dark matter candidates with distinctive experimental signatures. Ultralight dark matter generally requires a nonthermal origin to achieve the observed density, while still behaving like a pressureless fluid at late times. We show that such a production mechanism naturally occurs for vectors whose mass originates from a dark Higgs. If the dark Higgs has a large field value after inflation, the energy in the Higgs field can be efficiently transferred to vectors through parametric resonance. Computing the resulting abundance and spectra requires careful treatment of the transverse and longitudinal components, whose dynamics are governed by distinct equations of motion. We study these in detail and find that the mass of the vector may be as low as 10-18 eV, while making up the majority of the dark matter abundance. This opens up a wide mass range of vector dark matter as cosmologically viable, and further motivates the experimental searches for such particles. [ABSTRACT FROM AUTHOR]