Central pseudoscalar production in pp scattering and the gluon contribution to the proton spin

Central pseudoscalar production in $pp$ scattering is suppressed at small values of $Q_\perp$, where $Q$ is defined as the difference between the momenta transferred from the two protons. Such a behaviour is expected if the production occurs through the fusion of two vectors. Photon exchange could provide the dominant contribution at low transferred momenta, but we argue that an extension of the experiment could probe the gluon contribution to the proton spin.Comment: 12 pages, 2 figures and 3 tables, uses epsf.sty. Added references and tables. Minor changes include

Heavy-meson physics and flavour violation with a single generation

We study flavour-violating processes which involve heavy B- and D-mesons and are mediated by Kaluza-Klein modes of gauge bosons in a previously suggested model where three generations of the Standard Model fermions originate from a single generation in six dimensions. We find the bound on the size R of the extra spatial dimensions 1/R>3.3 TeV, which arises from the three-body decay B_s to K mu e. Due to the still too low statistics this bound is much less stringent than the constraint arising from K to mu e, 1/R>64 TeV, which was found in a previous work (Frere et al., JHEP, 2003). Nevertheless, we argue that a clear signature of the model would be an observation of K to mu e and B_s to K mu e decays without observations of other flavour and lepton number changing processes at the same precision level.Comment: 15 page

Contrasting patterns of selection between MHC I and II across populations of Humboldt and Magellanic penguins

Indexación: Web of ScienceThe evolutionary and adaptive potential of populations or species facing an emerging infectious disease depends on their genetic diversity in genes, such as the major histocompatibility complex (MHC). In birds, MHC class I deals predominantly with intracellular infections (e.g., viruses) and MHC class II with extracellular infections (e.g., bacteria). Therefore, patterns of MHC I and II diversity may differ between species and across populations of species depending on the relative effect of local and global environmental selective pressures, genetic drift, and gene flow. We hypothesize that high gene flow among populations of Humboldt and Magellanic penguins limits local adaptation in MHC I and MHC II, and signatures of selection differ between markers, locations, and species. We evaluated the MHC I and II diversity using 454 next-generation sequencing of 100 Humboldt and 75 Magellanic penguins from seven different breeding colonies. Higher genetic diversity was observed in MHC I than MHC II for both species, explained by more than one MHC I loci identified. Large population sizes, high gene flow, and/or similar selection pressures maintain diversity but limit local adaptation in MHC I. A pattern of isolation by distance was observed for MHC II for Humboldt penguin suggesting local adaptation, mainly on the northernmost studied locality. Furthermore, trans species alleles were found due to a recent speciation for the genus or convergent evolution. High MHC I and MHC II gene diversity described is extremely advantageous for the long term survival of the species.http://onlinelibrary.wiley.com/doi/10.1002/ece3.2502/epd

Neutrinos in flat extra dimension: towards a realistic scenario

We consider the simple extension of the Standard Model in which an additional right handed neutrino propagates along a flat extra dimension, while the Standard Model fields are confined on a 3-brane. The fifth dimension is $S^1/Z_2$ orbifold compactified. In this scenario, the neutrino mass can be naturally suppressed. By studying systematically the fundamental parameter space, we show that the strong phenomenological constraints on mixing angles between active and sterile neutrinos (especially those derived from the SNO experiment data) do not conflict with the possibility of generating a realistic neutrino mass spectrum. As a second step, we explore the possibility of a successful leptogenesis through the decays of the Kaluza-Klein excitations of the right handed neutrino.Comment: 16 pages, 2 ps figure

Meniscal tears: comparison of the conventional spin-echo and fast spin-echo techniques through image processing

Background: Conventional spin-echo (PD-CSE) and fast spin-echo (PD-FSE) techniques are frequently used to detect meniscal tears. However, the time delay for imaging with PD-CSE has resulted in its replacement with faster techniques, such as proton density fast spin-echo (PD-FSE), which has become a frequent tool at most diagnostic centres. Qualitative analysis shows that the PD-CSE technique is more sensitive, but other authors have not found significant differences between the aforementioned techniques. Therefore, we performed a quantitative analysis in this study that aims to measure differences in the quality of the images obtained with both techniques.Methods: We compared the PD-CSE and PD-FSE techniques by quantitatively analysing the obtained proton density images: the area shown, as well as the brightness and lesion contrast of the obtained image. A set of 100 images from 50 patients thought to contain meniscal tears of the knee were selected. These 100 images were obtained from all individuals using both the PD-CSE and PD-FSE techniques. the images were processed using software developed in Delphi. in addition to these quantifications, three physicians, who are specialists in radiology and capable of analysing magnetic resonance (MR) images of the musculoskeletal system, qualitatively analysed the diagnostic sensitivity of both techniques.Results: On average, samples obtained via the PD-CSE technique contained 22% more pixels in the lesion area. the contrast differed by 28%, and the brightness differed by 31%. the two techniques were correlated using Student's t-test, which showed a statistically significant difference. the specialists detected meniscal tears in 30 of the images obtained via the PD-CSE technique, while only 72% of these cases were detected via the PD-FSE technique.Conclusions: the PD-CSE technique was shown to be superior to PD-FSE for all of the evaluated properties, making its selection preferable.FAEP (Fundacao de Amparo a Ensino e Pesquisa) from Universidade de Mogi das CruzesUniv Mogi das Cruzes, Nucleo Pesquisas Tecnol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Diagnost Imagem EPM, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Diagnost Imagem EPM, São Paulo, BrazilWeb of Scienc

BRS Cedro e BRS Jatobá: cultivares de algodoeiro herbáceo recomendadas para os cerrados do Meio-Norte do Brasil.

bitstream/CPAMN-2009-09/18166/1/CT155.pd

CP Violation beyond the Standard Model

In this talk a number of broad issues are raised about the origins of CP violation and how to test the ideas.Comment: 17 pages, LaTeX, 6 postscript figures. Uses iopart10.clo, iopart12.clo and iopart.cls. Plenary talk given at the BSM Phenomenology Workshop, Durham, UK, 6-11 May 2001. To appear in the proceeding

Thermal production of axino Dark Matter

We reconsider thermal production of axinos in the early universe, adding: a) missed terms in the axino interaction; b) production via gluon decays kinematically allowed by thermal masses; c) a precise modeling of reheating. We find an axino abunance a few times larger than previous computations.Comment: 6 pages, 2 figures. Final version, to appear on JHE

Are the New Physics Contributions from the Left-Right Symmetric Model Important for the Indirect CP Violation in the Neutral B Mesons?

Several works analyzing the new physics contributions from the Left-Right Symmetric Model to the CP violation phenomena in the neutral B mesons can be found in the literature. These works exhibit interesting and experimentally sensible deviations from the Standard Model predictions but at the expense of considering a low right scale \upsilon_R around 1 TeV. However, when we stick to the more conservative estimates for \upsilon_R which say that it must be at least 10^7 GeV, no experimentally sensible deviations from the Standard Model appear for indirect CP violation. This estimate for \upsilon_R arises when the generation of neutrino masses is considered. In spite of the fact that this scenario is much less interesting and says nothing new about both the CP violation phenomenon and the structure of the Left-Right Symmetric Model, this possibility must be taken into account for the sake of completeness and when considering the see-saw mechanism that provides masses to the neutrino sector.Comment: LaTex file. 19 pages, 4 figures. Change in the way the paper address the problem. As a result, change in title, abstract, and some sections. Conclusions unchanged. Version to appear in Foundations of Physics Letter