We explain the cosmic ray positron-electron excess using a two component dark matter model. The two particle species in the dark matter sector are assumed to be in thermal equilibrium in the early universe. While one particle is stable and is the present day dark matter, the second one is metastable and decays after the universe is about a nanosecond old. In this model it is simple to accommodate the large apparent annihilation cross section of simple dark matter models, that are needed in order to explain the cosmic ray anomaly without large spikes in the local dark matter density.
COBISS.SI-ID: 22779943
We analyse the constraints on dimension-six Delta F=1 effective operators in models respecting the MFV hypothesis, both in the one-Higgs doublet case and in the two-Higgs doublet scenario with large tan beta. The constraints are derived mainly from the b -) s inclusive observables measured at the B factories. The implications of these bounds in view of improved measurements in exclusive and inclusive observables in b -) s l^+ l^- and s -) d nu nubar transitions are discussed.
COBISS.SI-ID: 22772007
We have developed a model independent framework to study the minimal flavor violation hypothesis. Methods known from nonlinear sigma models were used to describe the breaking of flavor symmetry in the standard model and to provide a book keeping framework for beyond standard model contributions resummed to all orders in large top yukawa couplings.
COBISS.SI-ID: 22999335
Motivated by the disagreement between experimental and lattice QCD results on the D_s decay constant we systematically reinvestigate role of leptoquarks in charm meson decays. We consider scalar leptoquarks that transform as a weak interaction triplet, doublet, or singlet in a model independent approach. Using the current experimental measurements in tau, kaon and charm sectors, we find that scalar leptoquarks cannot naturally explain the D_s --) mu nu and D_s --) tau nu decay widths simultaneously.
COBISS.SI-ID: 2203492
We performed the first lattice QCD simulation of tetraquarks, which uses the variational method. We determined the spectrum of the lightest scalar states with I= 0,1/2,1 using tetraquark interpolators, that had different spatial structure and the same color/spin structure. The ground states in all channels were found to be the scattering states, which are unaviodable. We did not find tetraquarks or the first excited scattering states and we presented analytical arguments for that. We proposed another set of interpolators, which lead to indication for tetraquarks in the next simulation.
COBISS.SI-ID: 22893607