Jožef Stefan Institute

About: Jožef Stefan Institute is a facility organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Liquid crystal & Dielectric. The organization has 3828 authors who have published 12614 publications receiving 291025 citations.

Yukawa sector in nonsupersymmetric renormalizable SO(10)

Abstract: We discuss the ordinary, nonsupersymmetric SO(10) as a theory of fermion masses and mixings. We construct two minimal versions of the Yukawa sector based on ${\overline{\mathbf{126}}}_{\mathbf{H}}$ and either ${\mathbf{10}}_{\mathbf{H}}$ or ${\mathbf{120}}_{\mathbf{H}}$. The latter case is of particular interest since it connects the absolute neutrino mass scale with the size of the atmospheric mixing angle ${\ensuremath{\theta}}_{A}$. It also relates the smallness of ${V}_{cb}$ with the largeness of ${\ensuremath{\theta}}_{A}$. These results are based on the analytic study of the second and third generations. Furthermore, we discuss the structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark matter and the predictivity of the theory.

Scattering phase shifts for two particles of different mass and nonzero total momentum in lattice QCD

Abstract: We derive the relation between the scattering phase shift and the two-particle energy in the finite box, which is relevant for extracting the strong phase shifts in lattice QCD. We consider elastic scattering of two particles with different mass and with nonzero total momentum in the lattice frame. This is a generalization of the L\"uscher formula, which considers zero total momentum, and a generalization of Rummukainen-Gottlieb's formula, which considers degenerate particles with nonzero total momentum. We focus on the most relevant total momenta in practice, i.e. $\mathbf{P}=(2\ensuremath{\pi}/L){e}_{z}$ and $\mathbf{P}=(2\ensuremath{\pi}/L)({e}_{x}+{e}_{y})$, including their multiples and permutations. We find that the $P$-wave phase shift can be reliably extracted from the two-particle energy if the phase shifts for $l\ensuremath{\ge}2$ can be neglected, and we present the corresponding relations. The reliable extraction of the $S$-wave phase shift is much more challenging since ${\ensuremath{\delta}}_{l=0}$ is always accompanied by ${\ensuremath{\delta}}_{l=1}$ in the phase shift relations, and we propose strategies for estimating ${\ensuremath{\delta}}_{l=0}$. We also propose the quark-antiquark and meson-meson interpolators that transform according the considered irreducible representations.

Light colored scalars from grand unification and the forward-backward asymmetry in tt̄ production

Abstract: The experimental results on the $t\overline{t}$ production cross section at the Tevatron are well described by the QCD contributions within the standard model, while the recently measured forward-backward asymmetry is larger than predicted within this framework. We consider light colored scalars appearing in a particular $SU(5)$ grand unified theory model within the 45-dimensional Higgs representation. A virtue of the model is that it connects the presence of a light colored $SU(2)$ singlet (${\ensuremath{\Delta}}_{6}$) and a color octet weak doublet (${\ensuremath{\Delta}}_{1}$) with bounds on the proton lifetime, which constrain the parameter space of both scalars. We find that both the total $t\overline{t}$ production cross section and the forward-backward asymmetry can be accommodated simultaneously within this model. The experimental results prefer a region for the mass of ${\ensuremath{\Delta}}_{6}$ around 400 GeV, while ${\ensuremath{\Delta}}_{1}$ is then constrained to have a mass around the TeV scale as well. We analyze possible experimental signatures and find that ${\ensuremath{\Delta}}_{6}$ associated top production could be probed in the $t\overline{t}+\mathrm{\text{jets}}$ final states at Tevatron and the LHC.

Structural and FTIR spectroscopic studies of gel-xerogel-oxide transitions of SnO 2 and SnO 2 : Sb powders and dip-coated films prepared via inorganic sol-gel route

Abstract: Sb doped and undoped SnO2 thin solid coatings were prepared by the dip-coating technique via the sol-gel route. Aqueous gels of undoped compound were made by using a SnCl4 precursor and doping was achieved through the addition of SbCl3 in the concentration range 1–10 mol%. Fourier transform infrared (FTIR), ATR and near normal reflectance spectroscopic techniques were utilized to determine the vibrational spectra of aqueous gels, xerogels and oxides of Sb doped and undoped compounds. Analysis of the corresponding FTIR spectra revealed the existence of Sb-O modes at 770 cm−1. The drying of both types of gel was accompanied by the formation of hydrogen bonds of medium strength wit the OH-O length about 2.7–2.8 A. Some properties of pure and Sb doped oxide powders formed in the temperature range ≤1000°C were measured by the thermogravimetry, X-ray diffraction and FTIR spectroscopic techniques. The doping brought about a broadening of the X-ray diffraction peaks. The reflectivity of the samples increased in the spectral range 4000-600 cm−1 up to 60%, due to the formation of plasma modes. Thin solids films were made by the dip-coating method. The efficiency of the dip-coating process was 0.02–0.1 μm per dipping, depending on the viscosity of the gel. The electrical resistivity of the doped SnO2 coatings was about 1.2 × 10−2 ω cm and thus comparable to the electrical resistivity of the alkoxide derived Sb doped SnO2. Doping decreased visible transmittance ∼5% but infrared reflectance increased up to 40%, depending on the film thickness.