We introduce the top-BESS model which is the effective description of the strong electroweak symmetry breaking with a single new SU(2)_L+R triplet vector resonance. The model is a modification of the BESS model in the fermion sector. The triplet couples to the third generation of quarks only. This approach reflects a possible extraordinary role of the top quark in the mechanism of electroweak symmetry breaking. The low-energy limits on the model parameters found provide hope for finding sizable signals in the LHC Drell-Yan processes as well as in the s-channel production processes at the ILC. However, there are regions of the model parameter space where the interplay of the direct and indirect fermion couplings can hide the resonance peak in a scattering process even though the resonance exists and couples directly to top and bottom quarks.Comment: published in Physical Review D, minor changes in text, 21 pages, 37 figure

Abstract. We fit the single-hadron transverse-momentum spectra measured in Pb+Pb collisions at √ s N N = 2.76 TeV with the blast-wave model that includes production via resonance decays. Common fit to pions, kaons, (anti)protons, and lambdas yields centrality dependence of the freeze-out temperature and transverse expansion velocity. In the most central collisions we see T = 98 MeV and v t = 0.654. The K * resonance fits into this picture but the φ meson might freeze-out a little earlier. Multistrange baryons seem to decouple at higher temperature and weaker transverse flow. Within our model we observe hints of chemical potential for the charged pions.

We fit the single-particle p t spectra of identified pions, kaons, and (anti)protons from central collisions of gold or lead nuclei at energies between 7.7 and 2760 GeV per nucleon pair. Blast wave model with included resonance production and with an assumption of partial chemical equilibrium is used and the fits are performed with the help of a Gaussian emulator process. A kinetic freeze-out temperature is found about 100 MeV for the lowest collision energies and 80 MeV at the LHC. The average transverse expansion velocity grows with increasing √ s N N from 0.45 to 0.65.Due to partial chemical equilibrium, the influence of resonance decays on the shape of the p t spectra for √ s N N above 27 GeV is small. PACS numbers: 25.75.-q,25.75.Dw,25.75.Ld

We propose an application of the Kolmogorov-Smirnov test for rapidity distributions of individual events in ultrarelativistic heavy ion collisions. The test is particularly suitable to recognise nonstatistical differences between the events. Thus when applied to a narrow centrality class it could indicate differences between events which would not be expected if all events evolve according to the same scenario. In particular, as an example we assume here a possible fragmentation of the fireball into smaller pieces at the quark/hadron phase transition. Quantitative studies are performed with a Monte Carlo model capable of simulating such a distribution of hadrons. We conclude that the Kolmogorov-Smirnov test is a very powerful tool for the identification of the fragmentation process.

Small neutrino masses can arise in some grand unified models or superstring theories. We consider a model with an enhanced fermion sector containing Dirac neutral heavy leptons. The dependence on the mass and mixing parameters of these new fermions is investigated for several measurable quantities.We study the flavor-conserving leptonic decays of the Z boson and universality breaking in these decays. We also consider the W boson mass dependence on neutral heavy lepton parameters. PACS numbers(s): 12.15.Ff, 13.38.Dg

Physics associated with the Higgs field potential is rich and interesting and deserves a concise summary for a broader audience to appreciate the beauty and the challenges of this subject. We discuss the role of the Higgs potential in particle physics, in particular in the spontaneous symmetry breaking and in the mass generation using an example of a simple reflection symmetry, then continue with the temperature and quantum corrections to the potential which lead us to the naturalness problem and the vacuum stability.

Naturally small neutrino masses can arise in some grand unified models. The mechanism of neutrino mass generation in these models typically requires the existence of neutral heavy leptons. We study the low-energy phenomenology of these new fermions. Concentrating on loop corrections due to neutral heavy leptons, we examine how the flavour-conserving leptonic decays of the Z boson, universality breaking in these decays, and the W boson mass depend on the mass and mixings of the neutral heavy leptons. Working within the framework of a superstring-inspired SU(2) L × U(1) Y model, we show that these flavour-conserving processes have some virtues over the traditionally considered flavour-violating decays.i

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