Electroweak Limits on General New Vector Bosons

We study extensions of the Standard Model with general new vector bosons. The full Standard Model gauge symmetry is used to classify the extra vectors and constrain their couplings. We derive the corresponding effective Lagrangian, valid at energies lower than the mass of the extra vectors, and use it to extract limits from electroweak precision observables, including LEP 2 data. We consider both universal and nonuniversal couplings to fermions. We study the interplay of several extra vectors, which can have the effect of opening new regions in parameter space. In particular, it allows to explain the anomaly in the bottom forward-backward asymmetry with perturbative couplings. Finally, we analyze quantitatively the implications for the Higgs mass.Comment: Latex 50 pages, 12 eps figures. Typos fixed, comments and references adde

Looking for signals beyond the neutrino Standard Model

Any new neutrino physics at the TeV scale must include a suppression mechanism to keep its contribution to light neutrino masses small enough. We review some seesaw model examples with weakly broken lepton number, and comment on the expected effects at large colliders and in neutrino oscillations.Comment: LaTeX 10 pages, 9 PS figures. Contribution to the Proceedings of the XXXI International School of Theoretical Physics "Matter To The Deepest" Ustron, Poland, September 5-11, 2007. Typos correcte

Impact of extra particles on indirect Z' limits

We study the possibility of relaxing the indirect limits on extra neutral vector bosons by their interplay with additional new particles. They can be systematically weakened, even below present direct bounds at colliders, by the addition of more vector bosons and/or scalars designed for this purpose. Otherwise, they appear to be robust.Comment: Latex 23 pages, 8 eps figures. Minor changes, version published in Phys. Rev.

Effect of solar cycle 23 in foF2 trend estimation

The effect of including solar cycle 23 in foF2 trend estimation is assessed using experimental values for Slough (51.5°N, 359.4°E) and Kokobunji (35.7°N, 139.5°E), and values obtained from two models: (1) the Sheffield University Plasmasphere-Ionosphere model, SUPIM, and (2) the International Reference Ionosphere, IRI. The dominant influence on the F2 layer is solar extreme ultraviolet (EUV) radiation, evinced by the almost 90% variance of its parameters explained by solar EUV proxies such as the solar activity indices Rz and F10.7. This makes necessary to filter out solar activity effects prior to long-term trend estimation. Solar cycle 23 seems to have had an EUV emission different from that deduced from traditional solar EUV proxies. During maximum and descending phase of the cycle, Rz and F10.7 seem to underestimate EUV solar radiation, while during minimum, they overestimate EUV levels. Including this solar cycle in trend estimations then, and using traditional filtering techniques, may induce some spurious results. In the present work, filtering is done in the usual way considering the residuals of the linear regression between foF2 and F10.7, for both experimental and modeled values. foF2 trends become less negative as we include years after 2000, since foF2 systematically exceeds the values predicted by a linear fit between foF2 and F10.7. Trends become more negative again when solar cycle 23 minimum is included, since for this period, foF2 is systematically lower than values predicted by the linear fit. foF2 trends assessed with modeled foF2 values are less strong than those obtained with experimental foF2 values and more stable as solar cycle 23 is included in the trend estimation. Modeled trends may be thought of as a ‘zero level’ trend due to the assumptions made in the process of trend estimation considering also that we are not dealing with ideal conditions or infinite time series.Fil: Elias, Ana Georgina. Universidad Nacional de Tucuman. Facultad de Ciencias Exactas y Tecnologia. Departamento de Fisica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Haro Barbás, Blas F.. Universidad Nacional de Tucuman. Facultad de Ciencias Exactas y Tecnologia. Departamento de Fisica; ArgentinaFil: Shibasaki, Kiyoto . Nobeyama Solar Radio Observatory; JapónFil: Souza, Jonas R.. Centro de Previsao de Tempo E Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; Brasi

Vacuum tribological behaviour of self lubricant quasicrystalline composite coatings

High temperature resistant self-lubricant coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys (QC) as the hard phase for wear resistance, have been deposited by thermal spray. The coatings also comprise lubricating materials (silver and BaF2-CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating belonging to this family, with excellent microstructural quality. The coating was deposited by HVOF and tested under vacuum on a pin-on-disc tribometer. Different loads, linear speeds and pin materials were studied. The pin scars and disc wear tracks were characterized by EDS-SEM. A minimum mean steady friction coefficient of 0.32 was obtained employing a X-750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin

Electroweak constraints on see-saw messengers and their implications for LHC

We review the present electroweak precision data constraints on the mediators of the three types of see-saw mechanisms. Except in the see-saw mechanism of type I, with the heavy neutrino singlets being mainly produced through their mixing with the Standard Model leptons, LHC will be able to discover or put limits on new scalar (see-saw of type II) and lepton (see-saw of type III) triplets near the TeV. If discovered, it may be possible in the simplest models to measure the light neutrino mass and mixing properties that neutrino oscillation experiments are insensitive to.Comment: 8 pages, 4 figures, To appear in the Proceedings of the Rencontres de Moriond 2008 EW Session, La Thuile (Italy), March 1-8, 200

Exploratory study of polycyclic aromatic hydrocarbons occurrence and distribution in manure pyrolysis products

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAH) have been investigated in the products derived from the pyrolysis of pig manure at low temperatures (<550 °C) in a fixed bed reactor. The focus was on the sixteen PAH identified as priority pollutants by the US Environment Protection Agency (EPA). The pyrolysis does not generate a significant additional amount of EPA-PAH to that existing in the original pig manure, under the operational conditions studied (<550 °C). While the total EPA-PAH yield does not indicate a notable dependence on the pyrolysis temperature, the EPA-PAH distribution among the three pig manure pyrolysis products as well as the speciation changed significantly with the temperature. The proportion of heavy PAH species increased as the temperature increased. The initial EPA-PAH in the manure samples plays a significant role in both their concentration and speciation in the biochar. The relationship of the EPA-PAH concentration and speciation in the biochar with those of the raw material was corroborated with a cow manure sample and the biochars obtained from its pyrolysis. For this reason, feedstocks with low EPA-PAH concentrations are recommended in order to obtain biochars with concentrations below the maximum allowed threshold established for their use as a soil enhancer by the International Biochar Initiative (IBI) and in the European Biochar Certificate

Vacuum Tribological Behaviour of Self-Lubricating Quasicrystalline Composite Coatings

High-temperature-resistant self-lubricating coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys as the hard phase for wear resistance can be deposited by a thermal spray technique. The coatings also contain lubricating materials (silver and BaF2CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating of this type, with a very good microstructural quality. The coating was deposited by high-velocity oxygen fuel spraying and tested under vacuum using a pin-on-disc tribometer. Different loads, linear speeds, and pin materials were studied. The pin scars and disc wear tracks were characterised using a combination of scanning electron microscopy and energy dispersive spectrometry. A minimum mean steady friction coefficient of 0.32 was obtained when employing an X750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pi