Z→bbˉZ\to b\bar b in U(1)RU(1)_R Symmetric Supersymmetry

We compute the one-loop corrections to the $Z \to b\bar{b}$ vertex in the $U(1)_R$ symmetric minimal supersymmetric extension of the standard model. We find that the predicted value of $R_b$ is consistent with experiment if the mass of the lighter top squark is no more than 180 GeV. Furthermore, other data combines to place a lower bound of 88 GeV on the mass of the light top squark. A top squark in this mass range should be accessible to searches by experiments at FNAL and LEP.Comment: Corrected typos; added footnotes and a reference. 19 pages, LaTeX, includes 8 figures, full postscript version at http://smyrd.bu.edu/htfigs/htfigs.htm

Universality-Breaking Effects in Leptonic Z Decays

We analyze the possibility of universality violation in diagonal leptonic decays of the $Z$ boson, in the context of interfamily "see-saw" models. In a minimal extension of the Standard Model with right-handed neutrino fields, we find that universality-breaking effects increase quadratically with the heavy Majorana neutrino mass and may be observed in the running $LEP$ experiments.Comment: MZ-TH/93-04 #, LaTeX, 14 p. (2 Figs

Study of the virus vector genus Trichodorus (Diphtherophorina, Trichodoridae) from the Iberian Peninsula, an apparent centre of speciation

Trichodoridae are polyphagous root ectoparasites occurring worldwide. Their major pest status is as virus vector of Tobraviruses. Currently, the family has 102 species classified within 6 genera. The genus Trichodorus is the largest in number of species (56) and predominantly occurs in temperate regions. Traditional morphology-based taxonomy revealed for Europe, a very high species diversity within the Iberian Peninsula, comprising about one fifth of all Trichodoridae described. Characteristic for this fauna is the presence of a morpho-species group within Trichodorus, characterized in males by slightly ventrally curved spicules with a mid-blade constriction with bristles and females with relatively large vaginal sclerotized pieces, quadrangular to triangular in shape. Recent surveys for Trichodoridae in cultivated and natural environments in Southern Spain and compared with the fauna from Portugal revealed four new species of Trichodorus, three of them belonging to this morpho-species group. Molecular analyses based on nuclear ribosomal RNA genes (D2-D3 expansion segments of 28S and partial 18S gene) supported not only the new species but also the morpho-species group as a separate clade. The integrated approach of morphology based taxonomy with molecular and biogeographic data enhanced the accuracy of the observed biodiversity and strengthen the hypothesis of the Iberian Peninsula as a center of speciation.The Society of Nematologists (SON

Integrative taxonomic study of the virus vector family Trichodoridae from the Iberian Peninsula, an apparent centre of speciation

Trichodoridae are polyphagous root ectoparasites occurring worldwide. Their major pest status is as virus vector of Tobraviruses. Currently, the family has 102 species classified within 6 genera. 88% of the species belong to the didelphic genera (females with two well developed genital branches) with the genus Trichodorus being the largest in number of species (56). Trichodorus species predominantly occur in temperate regions. Surveys for trichodorids were carried out in cultivated and natural habitats in Spain and compared with the trichodorid fauna from Portugal. A comparative morphological study was carried out together with molecular analyses based on nuclear ribosomal RNA genes (D2-D3 expansion segments of 28S and partial 18S gene). Characteristic for the Iberian Peninsula is the high number of morphologically closely resembling species but clearly separated molecularly (cryptic species), characterized in males by slightly ventrally curved spicules with a mid-blade constriction with bristles and females with relatively large vaginal sclerotized pieces, quadrangular to triangular in shape. Molecular analyses demonstrated that D2-D3 expansion segments are suitable diagnostic markers for Trichodoridae. Comparative morphology and molecular analyses provide support for the Iberian Peninsula as an apparent centre of speciation. South Africa is another known centre of speciation of Trichodorus.Nematological Society of Southern Afric

Probing leptogenesis

The focus of this paper lies on the possible experimental tests of leptogenesis scenarios. We consider both leptogenesis generated from oscillations, as well as leptogenesis from out-of-equilibrium decays. As the Akhmedov-Rubakov-Smirnov (ARS) mechanism allows for heavy neutrinos in the GeV range, this opens up a plethora of possible experimental tests, e.g. at neutrino oscillation experiments, neutrinoless double beta decay, and direct searches for neutral heavy leptons at future facilities. In contrast, testing leptogenesis from out-of-equilibrium decays is a quite difficult task. We comment on the necessary conditions for having successful leptogenesis at the TeV-scale. We further discuss possible realizations and their model specific testability in extended seesaw models, models with extended gauge sectors, and supersymmetric leptogenesis. Not being able to test high-scale leptogenesis directly, we present a way to falsify such scenarios by focusing on their washout processes. This is discussed specifically for the left-right symmetric model and the observation of a heavy WR, as well as model independently when measuring L = 2 washout processes at the LHC or neutrinoless double beta decay.Fil: Chun, E. J.. Korea Institute For Advanced Study; Corea del SurFil: Cvetic, G.. Universidad Técnica Federico Santa María; ChileFil: Dev, P. S. B.. Washington University in St. Louis; Estados UnidosFil: Drewes, Alejandro Marcelo. Technische Universitat München; Alemania. Université Catholique de Louvain; BélgicaFil: Fong, C. S.. Universidade de Sao Paulo; BrasilFil: Garbrecht, B.. Technische Universitat München; AlemaniaFil: Hambye, T.. Université Libre de Bruxelles; BélgicaFil: Harz, J.. Institut Lagrange de Paris, Sorbonne Universitès; Francia. Centre National de la Recherche Scientifique; FranciaFil: Hernández, P.. Cern - European Organization For Nuclear Research; Suiza. Universidad de Valencia; EspañaFil: Kim, C. S.. Department Of Physics And Ipap, Yonsei University; Corea del SurFil: Molinaro, E.. University Of Southern Denmark; DinamarcaFil: Nardi, E.. Laboratori Nazionali Di Frascati; ItaliaFil: Racker, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Rius, N.. Universidad de Valencia; EspañaFil: Zamora-Saa, J.. Joint Institute For Nuclear Research; Rusi

Charged Lepton Flavour Violation from Massive Neutrinos in Z Decays

Present evidences for neutrino masses and lepton flavour mixings allow to predict, in the Standard Model with light neutrinos, branching rates for the decays Z --> e mu, mu tau, e tau of less than 10^{-54}, while present experimental exclusion limits from LEP 1 are of order 10^{-5}. The GigaZ option of the TESLA Linear Collider project will extend the sensitivity down to about 10^{-8}. We study in a systematic way some minimal extensions of the Standard Model and show that GigaZ might well be sensitive to the rates predicted from these scenarios.Comment: 24 pages, 4 figures, LaTeX, uses axodraw.st

Challenges of viticulture adaptation to global change: tackling the issue from the roots

Viticulture is facing emerging challenges not only because of the effect of climate change on yield and composition of grapes, but also of a social demand for environmental-friendly agricultural management. Adaptation to these challenges is essential to guarantee the sustainability of viticulture. The aim of this review is to present adaptation possibilities from the soil-hidden, and often disregarded, part of the grapevine, the roots. The complexity of soil-root interactions makes necessary a comprehensive approach taking into account physiology, pathology and genetics, in order to outline strategies to improve viticulture adaptation to current and future threats. Rootstocks are the link between soil and scion in grafted crops, and they have played an essential role in viticulture since the introduction of phylloxera into Europe at the end of the 19th century. This review outlines current and future challenges that are threatening the sustainability of the wine sector and the relevant role that rootstocks can play to face these threats. We describe how rootstocks along with soil management can be exploited as an essential tool to deal with the effects of climate change and of emerging soil-borne pests and pathogens. Moreover, we discuss the possibilities and limitations of diverse genetic strategies for rootstock breeding.This work is framed in the networking activities of RedVitis (AGL2015-70931-REDT) and RedVitis 2.0 (AGL2017-90759-REDT), funded by the State Research Agency (AEI) of the Spanish Ministry of Science and Innovation. Ms Diana Marin is beneficiary of postgraduate scholarship funded by Universidad Publica de Navarra (FPI-UPNA-2016). Dr Juan Emilio Palomares-Rius acknowledges the State Research Agency (AEI) of the Spanish Ministry of Science and Innovation for the 'Ramon y Cajal' Fellowship RYC-2017-22228 and Dr David Gramaje acknowledges Spanish Ministry of Economy and Competitiveness for the 'Ramon y Cajal' Fellowship RYC-2017-23098

Forage Systems to Optimize Agronomic and Economic Performance in Organic Dairy Systems

Organic dairy production in the USA is growing, but most forage systems research focuses on conventional production practices. As a result, organic dairy producers have limited science-based information to assist with farm and livestock management. The objective of this project was to use a multi-faceted approach to determine the ideal species mixtures for organic dairy production as well as document forage quality, forage yield, soil characteristics, milk production and milk quality during the grazing season. The forages studied ranged from a single species monoculture to a four species mixture of warm and cool season grasses and legumes. Nine distinct forage systems were seeded into small plots at the University of Tennessee and University of Kentucky research farms using organic practices. These plots were monitored for three years for yield, quality, species composition, and soil characteristics. The four best performing forage systems were planted in small paddocks on organic dairy farms in Tennessee and Kentucky to evaluate forage yield, forage quality, seasonality of production, and suitability for on-farm milk production. The superior forage system was established on a 4 ha paddock and compared the existing forage system used by each of the dairy farms. These larger paddocks allowed continued measurements of forage yield and quality, as well as measurements of milk production, milk quality, and grazing behaviour of the animals. The information from this project is currently being incorporated into a total farm management system for organic dairy producers in the Southeastern USA

A Note on Charge Quantization Through Anomaly Cancellation

In a minimal extension of the Standard Model, in which new neutral fermions have been introduced, we show that the requirement of vanishing anomalies fixes the hypercharges of all fermions uniquely. This naturally leads to electric charge quantization in this minimal scenario which has features similar to the Standard Model: invariance under the gauge group $SU(2)_L\otimes U(1)_Y$, conservation of the total lepton number and masslessness for the ordinary neutrinos. Such minimal models might arise as low-energy realizations of some heterotic superstring models or $SO(10)$ grand unified theories.Comment: 14p., TeX, (final version