307 research outputs found
Charged Higgs Production in the 1 TeV Domain as a Probe of Supersymmetric Models
We consider the production, at future lepton colliders, of charged Higgs
pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and
working in the MSSM, we show that, for c.m. energies in the one TeV range, a
one-loop logarithmic Sudakov expansion that includes an "effective" next-to
subleading order term is adequate to the expected level of experimental
accuracy. We consider then the coefficient of the linear (subleading) SUSY
Sudakov logarithm and the SUSY next to subleading term of the expansion and
show that their dependence on the supersymmetric parameters of the model is
drastically different. In particular the coefficient of the SUSY logarithm is
only dependent on while the next to subleading term depends on a
larger set of SUSY parameters. This would allow to extract from the data
separate informations and tests of the model.Comment: 18 pages and 13 figures e-mail: [email protected]
SUSY Scalar Production in the Electroweak Sudakov Regime of Lepton Colliders
We consider the production of SUSY scalar pairs at lepton colliders, for c.m.
energies much larger than the mass of the heaviest SUSY (real or virtual)
particle involved in the process. In that energy regime, we derive the leading
and subleading terms of the electroweak Sudakov logarithms in the MSSM, first
working at one loop with physical states and then resumming to all orders with
asymptotic expansions. We show that the first order of the resummed expression
reproduces the physical one loop approximation, and compute systematically the
possible effects on various observables both at one loop and to all orders. We
discuss the regimes and the processes where the one loop approximation can or
cannot be trusted, working in an energy range between 1 TeV and 4 TeV under a
"light" SUSY mass assumption. As a byproduct of our analysis, we propose a
determination of the MSSM parameter tan(beta) showing how a relative accuracy
of about 25 percent can be easily achieved in the region tan(beta)>14, under
reasonable experimental assumptions.Comment: 35 pages and 15 figures e-mail: [email protected]
Resummation of Yukawa enhanced and subleading Sudakov logarithms in longitudinal gauge boson and Higgs production
Future colliders will probe the electroweak theory at energies much larger
than the gauge boson masses. Large double (DL) and single (SL) logarithmic
virtual electroweak Sudakov corrections lead to significant effects for
observable cross sections. Recently, leading and subleading universal
corrections for external fermions and transverse gauge boson lines were
resummed by employing the infrared evolution equation method. The results were
confirmed at the DL level by explicit two loop calculations with the physical
Standard Model (SM) fields. Also for longitudinal degrees of freedom the
approach was utilized for DL-corrections via the Goldstone boson equivalence
theorem. In all cases, the electroweak Sudakov logarithms exponentiate. In this
paper we extend the same approach to both Yukawa enhanced as well as subleading
Sudakov corrections to longitudinal gauge boson and Higgs production. We use
virtual contributions to splitting functions of the appropriate Goldstone
bosons in the high energy regime and find that all universal subleading terms
exponentiate. The approach is verified by employing a non-Abelian version of
Gribov's factorization theorem and by explicit comparison with existing one
loop calculations. As a side result, we obtain also all top-Yukawa enhanced
subleading logarithms for chiral fermion production at high energies to all
orders. In all cases, the size of the subleading contributions at the two loop
level is non-negligible in the context of precision measurements at future
linear colliders.Comment: 32 pages, 7 figures, uses LaTeX2
The role of universal and non universal Sudakov logarithms in four fermion processes at TeV energies: the one-loop approximation revisited
We consider the separate effects on four fermion processes, in the TeV energy
range, produced at one loop by Sudakov logarithms of universal and not
universal kind, working in the 't Hooft xi=1 gauge. Summing the various vertex
and box contributions allows to isolate two quite different terms.The first one
is a combination of vertex and box quadratic and linear logarithms that are
partially universal and partially not universal and independent of the
scattering angle theta. The second one is theta-dependent, not universal,
linearly logarithmic and only produced by weak boxes. We show that for several
observables, measurable at future linear e+e- colliders (LC, CLIC), the role of
the latter term is dominant and we discuss the implications of this fact for
what concerns the reliability of a one-loop approximation.Comment: 22 pages and 13 figures; version to appear in Phys.Rev.D. e-mail:
[email protected]
Caracterização fenotípica e genética de cepas de Bordetella pertussis isoladas em São Paulo, Brasil, 1988-2002
Whooping cough or pertussis was a major cause of childhood morbidity and mortality in the world until the introduction of a whole-cell vaccine in the 1940's. However, since the early 1980's whooping cough cases have increased in many countries, becoming an important problem of public health. This increase may be due to accuracy of laboratory diagnosis and reporting of the disease, a decline in immunity over time, demographic changes, and adaptation of the bacterial population to vaccine-induced immunity. The purpose of this study was to analyze phenotypically and genotypically a collection of 67 Bordetella pertussis isolates recovered during the period 1988-2002 in São Paulo State, Brazil to determine their characteristics and relatedness. All isolates were submitted to susceptibility testing to erythromycin, serotyping, and 56 isolates were analyzed by Pulsed Field Gel Electrophoresis (PFGE). All isolates were susceptible to erythromycin and the majority of them belonged to serotype 1,3. The 56 isolates were classified into 11 PFGE profiles according to the differences in banding patterns. Although more than 60% of the isolates were recovered from patients aged less than three months, almost 15% of them were isolated from adolescents/adults evidencing the increase in the incidence of pertussis among this group of age.A coqueluche ou pertussis foi a maior causa de morbidade e mortalidade infantil em todo o mundo até a introdução de uma vacina na década de 1940. Entretanto, desde a década de 1980, a coqueluche tornou-se, em muitos países , um importante problema de saúde pública. Este acontecimento pode ser atribuído à melhoria do diagnóstico laboratorial e da notificação da doença, declínio da imunidade no decorrer do tempo, mudanças demográficas ou adaptação da população bacteriana à imunidade induzida pela vacina. O objetivo deste estudo foi analisar as características fenotípicas e genotípicas de uma coleção de 67 cepas de Bordetella pertussis isoladas no período 1988-2002 em São Paulo, Brasil. Todas as cepas foram submetidas à determinação do perfil de resistência à eritromicina, à sorotipagem e 56 cepas à eletroforese em campo pulsado (PFGE). Todas as cepas foram sensíveis à eritromicina e a maioria delas pertencia ao sorotipo 1,3. As 56 cepas foram classificadas em 11 perfis de PFGE com base nas diferenças no padrão de bandas. Embora mais de 60% das cepas tenham sido isoladas de crianças com menos de três meses de idade, cerca de 15% delas era de adolescentes/adultos evidenciando um aumento da incidência da coqueluche nesse grupo etário
The Atlantic Ocean at the last glacial maximum: 1. Objective mapping of the GLAMAP sea-surface conditions
Recent efforts of the German paleoceanographic community have resulted in a unique data set of reconstructed sea-surface temperature for the Atlantic Ocean during the Last Glacial Maximum, plus estimates for the extents of glacial sea ice. Unlike prior attempts, the contributing research groups based their data on a common definition of the Last Glacial Maximum chronozone and used the same modern reference data for calibrating the different transfer techniques. Furthermore, the number of processed sediment cores was vastly increased. Thus the new data is a significant advance not only with respect to quality, but also to quantity. We integrate these new data and provide monthly data sets of global sea-surface temperature and ice cover, objectively interpolated onto a regular 1°x1° grid, suitable for forcing or validating numerical ocean and atmosphere models. This set is compared to an existing subjective interpolation of the same base data, in part by employing an ocean circulation model. For the latter purpose, we reconstruct sea surface salinity from the new temperature data and the available oxygen isotope measurements
Binary IS Typing for Staphylococcus aureus
Background: We present an easily applicable test for rapid binary typing of Staphylococcus aureus: binary interspace (IS) typing. This test is a further development of a previously described molecular typing technique that is based on length polymorphisms of the 16S-23S rDNA interspace region of S. aureus. Methodology/Principal Findings: A novel approach of IS-typing was performed in which binary profiles are created. 424 human and animal derived MRSA and MSSA isolates were tested and a subset of these isolates was compared with multi locus sequence typing (MLST) and Amplified Fragment Length Polymorphism (AFLP). Binary IS typing had a high discriminatory potential and a good correlation with MLST and AFLP. Conclusions/Significance: Binary IS typing is easy to perform and binary profiles can be generated in a standardized fashion. These two features, combined with the high correlation with MLST clonal complexes, make the techniqu
Electroweak corrections to W-boson pair production at the LHC
Vector-boson pair production ranks among the most important Standard-Model
benchmark processes at the LHC, not only in view of on-going Higgs analyses.
These processes may also help to gain a deeper understanding of the electroweak
interaction in general, and to test the validity of the Standard Model at
highest energies. In this work, the first calculation of the full one-loop
electroweak corrections to on-shell W-boson pair production at hadron colliders
is presented. We discuss the impact of the corrections on the total cross
section as well as on relevant differential distributions. We observe that
corrections due to photon-induced channels can be amazingly large at energies
accessible at the LHC, while radiation of additional massive vector bosons does
not influence the results significantly.Comment: 29 pages, 15 figures, 4 tables; some references and comments on
\gamma\gamma -> WW added; matches version published in JHE
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