Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Searches for heavy Higgs bosons in two-Higgs-doublet models and for t→ch decay using multilepton and diphoton final states in pp collisions at 8 TeV

Searches are presented for heavy scalar (H) and pseudoscalar (A) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of pp collisions collected with the CMS experiment at the LHC at a center-of-mass energy of root s = 8 TeV and corresponding to an integrated luminosity of 19.5 fb(-1). The decays H -> hh and A -> Zh, where h denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. The search results are presented in terms of the H and A production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% C.L. cross section upper limits of approximately 7 pb on sigma B for H -> hh and 2 pb for A -> Zh. Also presented are the results of a search for the rare decay of the top quark that results in a charm quark and an SM Higgs boson, t -> ch, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% C.L. upper limit of 0.56% on B(t -> ch).

Immunolocalization of myosin Va in the developing nervous system of embryonic chicks

Myosins are molecular motors associated with the actin cytoskeleton that participate in the mechanisms of cellular motility. During the development of the nervous system, migration of nerve cells to specific sites, extension of growth cones, and axonal transport are dramatic manifestations of cellular motility. We demonstrate, via immunoblots, the expression of myosin Va during early stages of embryonic development in chicks, extending from the blastocyst period to the beginning of the fetal period. The expression of myosin Va in specific regions and cellular structures of the nervous system during these early stages was determined by immunocytochemistry using a polyclonal antibody. Whole mounts of chick embryos at 24-30-h stages showed intense immunoreactivity of the neural tube in formation along its full extent. Cross-sections at these stages of development showed strong labeling in neuroepithelial cells at the basal and apical regions of the neural tube wall. Embryos at more advanced periods of development (48h and 72 h) showed distinctive immunolabeling of neuroepithelial cells, neuroblasts and their cytoplasmic extensions in the mantle layer of the stratified neural tube wall, and neuroblasts and their cytoplasmic extensions in the internal wall of the optic cup, as well as a striking labeling of cells in the apparent nuclei of cranial nerves and budding fibers. These immunolocalization studies indicate temporal and site-specific expression of myosin Va during chick embryo development, suggesting that myosin Va expression is related to recruitment for specific cellular tasks.

IR-visible upconversion and thermal effects in Pr3+/Yb3+-codoped Ga2O3 : La2S3 chalcogenide glasses

IR-visible upconversion fluorescence spectroscopy and thermal effects in pr(3+)/Yb3+-codoped Ga2O3:La2S3 chalcogenide glasses excited at 1.064 mum is reported. Intense visible upconversion emission in the wavelength region of 480-680 nm peaked around 500, 550, 620 and 660 nm is observed. Upconversion excitation of the Pr3+ excited-state visible emitting levels is achieved by st combination of phonon-assisted absorption, energy-transfer and phonon-assisted excited-state absorption processes. A threefold upconversion emission enhancement induced by thermal effects when the codoped sample was heated in the temperature range of 20-200 degreesC is demonstrated. The thermal-induced enhancement is attributed to a multiphonon-assisted anti-Stokes process which takes place in the excitation of the ytterbium and excited-state absorption of the praseodymium. The thermal effect is modelled by conventional rate equations considering temperature-dependent effective absorption cross-sections for the F-2(7/2)-F-2(5/2) ytterbium transition and (1)G(4)-P-3(0) praseadymium excited-state absorption, and it is shown to agree very well with experimental results. Frequency upconversion in singly Pr3+-doped samples pumped at 836 nm and 1.064 mum in a two-beam configuration is also examined.

NN -> NN pi(+) reaction near threshold in a chiral power counting approach

Power-counting arguments are used to organize the interactions contributing to the NN-->d pi,pn pi reactions near threshold. We estimate the contributions from the three formally leading mechanisms: the Weinberg-Tomozawa (WT) term, the impulse term, and the Delta-excitation mechanism. Subleading but potentially large mechanisms, including S-wave pion rescattering, the Galilean correction to the WT term, and short-ranged contributions are also examined. The WT term is shown to be numerically the largest, and the other contributions are found to approximately cancel. Similarly to the reaction pp-->pp pi(0), the computed cross sections are considerably smaller than the data. We discuss possible origins of this discrepancy.

Soft color enhancement of the production of J/psi's by neutrinos

We calculate the production of J/ψ mesons by neutrino-nucleon collisions in fixed target experiments. Soft color, often referred to as color evaporation effects, enhances production cross sections due to the contribution of color octet states. Though still small, J/ψ production may be observable in present and future experiments such as NuTeV and μ colliders. ©2001 The American Physical Society.

Infecção por strigea falconis em buteo magnirostris no Brasil

Background: Buteo magnirostris, popularly known as roadside hawk belongs to the family Accipitridae, Ciconiiformes. The specimen is common throughout Brazil inhabiting open areas, tolerating disturbed areas very well, but avoiding dense forests. The trematodes are common parasites in the intestines of birds of prey, with scant notice of pathogenic infections. However, severe infections of trematodes Strigeidae family have been previously reported as a cause of anemia, diarrhea, enteritis, weight loss and death. This paper aims to report the occurrence of infection in S. Falconis in B. magnirostris diagnosed by post mortem examination. Case: The specimen of B. magnirostris, male, young was sent for necropsy at the Laboratory of Veterinary Pathology, Federal Rural University of Semi-Arid (UFERSA), Mossoró-RN, Brazil. With a history of apathy, anorexia, diarrhea and death in one course of 24 h. The free bird life and even puppy had been captured for training and practice of falconry shortly before the clinical manifestation of infection (time of captivity uninformed). On physical examination ruffled feathers, cachexia and pallor of skeletal muscle was observed. At necropsy there was severe enteritis with petechiae and accumulation of liquid contents into the duodenum. Fifty-two trematodes were found set in duodenal mucosa. The other organs and structures showed no changes. Fragments of all organs were harvested, fixed in 10% formalin buffered, routinely processed for histopathology and stained with hematoxylin and eosin (HE). Parasites were carefully collected, washed in saline, fixed, processed and identified according to the morphology and taxonomy. Histologically, the lesions were restricted to the duodenum and were characterized by melting, severe atrophy and necrosis of the epithelial cells of the intestinal villi; inflammatory infiltrate (consisting of lymphocytes, plasma cells and eosinophils) in the lamina propria, in addition to trematodes infiltrated the mucosa and lamina propria. These were 60-80 mm in diameter, consisted of parenchymal body enclosed by the integument. In some cross sections of the parasite was possible to observe the presence of cecum, testis and uterus, with some variations between sections; there were also yellowish eggs and coated with a delicate membrane. The trematodes contain approximately 1 mm in length and used as morphology and taxonomy has been identified as S. Falconis. Discussion: S. Falconis is a trematode intestinal parasite of birds of prey, with reports of its occurrence in Europe, North America and Central. In neotropical regions is described the occurrence of the subspecies S. Falconis brasiliana. Although the absence of clinical signs is a common pattern, parasitism by trematodes may become evident, common to captivity stress conditions, and thus infections, even for low pathogenic parasites can cause diarrhea, anorexia, weight loss and death, as reported in this paper. A factor that possibly contributed to the scant notice is its small size, which makes the observation of this parasite in analysis of necropsy in non-pathological conditions and also not familiar with the technical laboratories in the morphological shape of the eggs, which creates difficulty in finding the parasite in parasitological analysis in captive animals. Despite being considered poorly pathogenic trematodes, epidemiologically, the presence of the parasite should be considered a health risk to free-living predators, newly captive in parks, zoos, veterinary hospitals, triage center for wildlife and creators, as they may express pathogenicity in immunosuppressed animals. This work contributes to recording the presence S. falconis parasitizing the duodenal mucosa of B. magnirostris in Brazil.

Teorias semiclássica e efetiva da gravitação

Pós-graduação em Física - IFT