60 resultados para sivers asymmetries


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Several left-right parity violating asymmetries in lepton-lepton scattering in fixed target and collider experiments are considered as signals for doubly charged vector bosons (bileptons).

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Several parity-violating left-right asymmetries in Miller electron-electron and muon-muon scattering are considered in the context of the electroweak standard model at the tree level in fixed target and collider experiments. We show that in colliders the asymmetry with only one of the beams polarized is large enough to compensate the smaller cross section at high energies. We also show that these asymmetries are very sensitive to a doubly charged vector bilepton resonance but they are insensitive to scalar ones.

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By considering left-right (L-R) asymmetries we study the capabilities of lepton colliders in searching for new exotic vector bosons. Specifically we study the effect of a doubly charged bilepton boson and an extra neutral vector boson appearing in a 3-3-1 model on the L-R asymmetries for the processes e-e- → e-e-, μ-μ- → μ-μ- and e-μ- → e-μ- and show that these asymmetries are very sensitive to these new contributions and that they are in fact powerful tools for discovery of this sort of vector bosons.

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Introduction: Our objective was to determine the perception of smile esthetics among orthodontists and laypeople with respect to asymmetries on the maxillary incisor edges in a frontal smile analysis. Methods: Two frontal close-up smile photos of 2 women, 1 white and 1 Afro-Brazilian, were selected for this study. Both smiles displayed healthy maxillary anterior dentitions. The images were digitally altered to create tooth wear on the maxillary left central and lateral incisors in 0.5-mm increments. The final images were randomly assembled into a photo album that was given to 120 judges, 60 orthodontists and 60 laypersons. Each rater was asked to evaluate the attractiveness of the images with visual analog scales. The data collected were statistically analyzed with 1-way analysis of variance with the Tukey post-hoc test and the unpaired Student t test. Results: The most attractive smiles in both types of smiles were those without asymmetries and the 0.5-mm wear in the lateral incisor. In general, tooth wear was considered unattractive by both groups of raters following a pattern: the more tooth wear, the more unattractive the smile; tooth wear in the central incisor was considered more unattractive than in the lateral incisor. For both group of raters, 0.5 mm of wear in the central incisor was considered unattractive, whereas the thresholds for lateral incisor discrepancies were 0.5 mm for orthodontists and 1.0 mm for laypersons. Conclusions: The result of this study corroborates the clinical assumption that symmetry between the maxillary central incisors is a paramount goal for esthetic treatments. Copyright © 2013 by the American Association of Orthodontists.

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We consider, in the electroweak standard model context, several left-right asymmetries in μe elastic scattering at fixed target and collider experiments. For the former case, we show that the muon mass effects are important in a wide energy range. We also show that these asymmetries are sensitive to the electroweak mixing angle θW. The effect of an extra Z' neutral vector boson appearing in a 3-3-1 model is also considered. The capabilities of these asymmetries in the search of this extra Z' are addressed.

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Purpose: To verify if uterine cerclage can induce craniosynostosis or any cranial deformity in new born Wistar rats. Methods: One pregnant female Wistar rat underwent laparotomy on day 18 of gestation and the uterus cervix was closed with a 3-0 nylon suture to avoid delivery, that occurs normally on the 21 day. The suture was released after 48 hours beyond the normal gestation period. The female rat delivered 11 pups. Six surviving rats from the delivery (group A - constrained group). Two rats were born from another mother and in the same age were used as control group (group B - 2 nonconstrained controls) were allowed to grow. They were sacrificed 1.2 years after their birth all the eight animals. Linear measurement, routine histology and computed tomography of the skull were performed at the time of their death to evaluate the cranial asymmetries by mesurements of the anatomical landmarks of the craniofacial skeleton of the rats on the two groups and compared then. Results: We did not observe statistically significant differences in any of the compared measurements (p>0.05) obtained through the morphologic and radiologic methods. Histologic examinations did not reveal any sign of premature fusion or suture imbrications. Critical decrease in longitudinal body size was noticed as the limbs too in all the animals of group A. Conclusion: Constriction of uterine cervix leads to fetus suffering, even death for a few animals, associated to small body size, but not to craniosynostosis.

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Several left-right asymmetries in Moller (electron-electron), muon-muon and electron-muon scattering are considered in the context of the electroweak standard model and in a model with SU(3)(C) x SU(3)(L) x U(1)(Y) gauge symmetry at tree level in collider experiments. We show that these asymmetries are very sensitive to a doubly charged vector bilepton in the case of ee and mu mu colliders and to an extra Z' neutral vector boson contribution in e(-)mu (-) collider.

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We use a version of the meson cloud model, including the kaon and the K-* contributions, to estimate the electric and magnetic strange form factors of the nucleon. We compare our results with the recent measurements of the strange quark contribution to parity-violating asymmetries in the forward G0 electron-proton scattering experiment. We conclude that it is very important to determine experimentally the electric and magnetic strange form factors, and not only the combination G(E)(s)+eta G(M)(s), if one does really intend to understand the strangeness of the nucleon.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)