[en] If the Higgs boson mass is (125 ± 1) GeV, the standard model cannot be a fundamental theory up to the GUT (Grand Unification) scale due to the vacuum stability arguments. We show that if the dark matter of the Universe consists of stable scalar particles, the vacuum stability constraints are modified and the theory can be valid up to a high scale. We argue that the present LHC data may favour such a scenario. (authors)

[en] We show that if the Higgs boson mass is (125 ± 1) GeV, the CMSSM (Constrained Minimal Supersymmetric Standard Model) sparticle spectrum that is testable at the LHC is restricted only to two distinct possibilities - either of the lightest s-lepton or stop are degenerate in mass with the lightest supersymmetric particle that is the dark matter. This implies that the CMSSM spectrum is now known. However, the two possible options both represent very difficult spectra for the LHC because very soft particles are produced in sparticle decays. We encourage the LHC experiments to perform detailed studies of the two possible CMSSM sparticle spectra. (authors)

[en] We study the impact of semi-annihilations χχ ↔ χX; where χ is dark matter and X is any standard model particle, on dark matter phenomenology. We formulate scalar dark matter models with minimal field content that predict non-trivial dark matter phenomenology for different discrete Abelian symmetries Z_N, N > 2, and contain semi-annihilation processes. We implement such an example model in micrOMEGAs and show that semi-annihilations modify the phenomenology of this type of models. (authors)

[en] We consider classically scale-invariant theories with non-minimally coupled scalar fields, where the Planck mass and the hierarchy of physical scales are dynamically generated. The classical theories possess a fixed point, where scale invariance is spontaneously broken. In these theories, however, the Planck mass becomes unstable in the presence of explicit sources of scale invariance breaking, such as non-relativistic matter and cosmological constant terms. We quantify the constraints on such classical models from Big Bang Nucleosynthesis that lead to an upper bound on the non-minimal coupling and require trans-Planckian field values. We show that quantum corrections to the scalar potential can stabilise the fixed point close to the minimum of the Coleman-Weinberg potential. The time-averaged motion of the evolving fixed point is strongly suppressed, thus the limits on the evolving gravitational constant from Big Bang Nucleosynthesis and other measurements do not presently constrain this class of theories. Field oscillations around the fixed point, if not damped, contribute to the dark matter density of the Universe.

[en] Within the framework of scalar-tensor theories, we study the conditions that allow single field inflation dynamics on small cosmological scales to significantly differ from that of the large scales probed by the observations of cosmic microwave background. The resulting single field double inflation scenario is characterised by two consequent inflation eras, usually separated by a period where the slow-roll approximation fails. At large field values the dynamics of the inflaton is dominated by the interplay between its non-minimal coupling to gravity and the radiative corrections to the inflaton self-coupling. For small field values the potential is, instead, dominated by a polynomial that results in a hilltop inflation. Without relying on the slow-roll approximation, which is invalidated by the appearance of the intermediate stage, we propose a concrete model that matches the current measurements of inflationary observables and employs the freedom granted by the framework on small cosmological scales to give rise to a sizeable population of primordial black holes generated by large curvature fluctuations. We find that these features generally require a potential with a local minimum. We show that the associated primordial black hole mass function is only approximately lognormal.

[en] We reconsider complex scalar singlet dark matter stabilised by a ℤ₃ symmetry. We refine the stability bounds on the potential and use constraints from unitarity on scattering at finite energy to place a stronger lower limit on the direct detection cross section. In addition, we improve the treatment of the thermal freeze-out by including the evolution of the dark matter temperature and its feedback onto relic abundance. In the regions where the freeze-out is dominated by resonant or semi-annihilation, the dark matter decouples kinetically from the plasma very early, around the onset of the chemical decoupling. This results in a modification of the required coupling to the Higgs, which turns out to be at most few per cent in the semi-annihilation region, thus giving credence to the standard approach to the relic density calculation in this regime. In contrast, for dark matter mass just below the Higgs resonance, the modification of the Higgs invisible width and direct and indirect detection signals can be up to a factor 6.7. The model is then currently allowed at 56.8 GeV to 58.4 GeV (depending on the details of early kinetic decoupling) ≲ M_S ≲ 62.8 GeV and at M_S ≳ 122 GeV if the freeze-out is dominated by semi-annihilation. We show that the whole large semi-annihilation region will be probed by the near-future measurements at the XENONnT experiment.

[en] The evidence for a new neutral scalar particle from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far, suggests the existence of new coloured scalars. To study this possibility, we propose a supersymmetry inspired simplified model, extending the Standard Model with a singlet scalar and with heavy scalar fields carrying both colour and electric charges – new scalar quarks. To allow the latter to decay, and to generate the dark matter of the Universe, we also add a neutral fermion to the particle content. We show that this model provides a two-parameter fit to the observed diphoton excess consistently with cosmology, while the allowed parameter space is bounded by the consistency of the model. In the context of our simplified model this implies the existence of other supersymmetric particles accessible at the LHC, rendering this scenario falsifiable.

[en] The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such scalars appear in Multi-Higgs-Doublet models, in particular in the popular Two-Higgs-Doublet model, allowing for charged and additional neutral Higgs bosons. These models have the attractive property that electroweak precision observables are automatically in agreement with the Standard Model at the tree level. For the most popular version of this framework, Model II, a discovery of a charged Higgs boson remains challenging, since the parameter space is becoming very constrained, and the QCD background is very high. We also briefly comment on models with dark matter which constrain the corresponding charged scalars that occur in these models. The stakes of a possible discovery of an extended scalar sector are very high, and these searches should be pursued in all conceivable channels, at the LHC and at future colliders. (orig.)