Using lattice QCD, we presented the first study of charmonium resonances taking intoaccount their strong decay. The mass and the decay width of the lowest charmonium vector resonance ψ(3770) was determined by simulating the scattering of DD ¯ in p-wave. The results are in favourable agreement with the experimental mass and width. The scattering matrix for DD ¯ scattering in s-wave was also determined, which is relevant for scalar charmonium resonance. Only the ground state charmonium χc1(1P) is known, while the experimental candidate for its first excitation is still not commonly accepted at present. Our results shed light on this open problem and indicate a possible existence of a scalar charmonium state with a mass between 3.9 and 4.0 GeV. Further lattice simulations and experimental results will be needed to resolve this open problem.

COBISS.SI-ID: 2847588

We investigated the phenomenology of flavored dark matter (DM). DM stability is guaranteed by an accidental Z3 symmetry, a subgroup of the standard model (SM) flavor group that is not broken by the SM Yukawa interactions. We considered an explicit realization where the quark part of the SM flavor group is fully gauged. If the dominant interactions between DM and visible sector are through flavor gauge bosons, as we showed for Dirac fermion flavored DM, then the DM mass is bounded between roughly 0.5 TeV and 5 TeV if the DM multiplet mass is split only radiatively. In general, however, no such relation exists. We demonstrated this using scalar flavored DM where the main interaction with the SM is through the Higgs portal. For both cases we derived constraints from flavor, cosmology, direct and indirect DM detection, and collider searches.

COBISS.SI-ID: 29148455

Prompted by the recent experimental hint of h → τμ events by the CMS Collaboration, we have carefully examined the implications of lepton flavor violating (LFV) Higgs decays at the percent level on possible extensions of the Standard Model. In particular we have shown how a tentative B(h → τμ) signal can be combined with other Higgs measurements to yield a robust lower bound on the effective LFV Higgs Yukawa couplings to taus and muons. Then we have reexamined the connection between LFV Higgs decays and LFV radiative decays of charged leptons, and demonstrated using effective field theory methods that the current hint from the CMS experiment implies τ → μγ at rates, which could be observable at the Belle II experiment. In explicit models, the τ → μγ constraint is generically much more severe.

COBISS.SI-ID: 28675111

We show that supersymmetric E6 Grand Unified Theory with a Higgs sector consisting of 27, 351 and 78 dimensional representations provides a realistic scenario for symmetry breaking and fermion mass generation. The Yukawa sector consists of only two symmetric matrices describing all of quark and neutrino masses and mixings. This model, having 11 superpotential parameters, alongside the two symmetric Yukawa matrices, seems to be the best realistic candidate for a minimal renormalizable supersymmetric E6 unified theory.

COBISS.SI-ID: 29033767

We show that within the Left-Right symmetric model, lepton number violating decays of the Higgs boson can be discovered at the LHC. The process is due to the mixing of the Higgs with the triplet that breaks parity. As a result, the Higgs can act as a gateway to the origin of heavy Majorana neutrino mass. To assess the LHC reach, a detailed collider study of the same-sign di-leptons plus jets channel is provided. This process is complementary to the existing nuclear and collider searches for lepton number violation and can probe the scale of parity restoration even beyond other direct searches.

COBISS.SI-ID: 28795175