384 resultados para Rare collisions
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Rare collisions of a classical particle bouncing between two walls are studied. The dynamics is described by a two-dimensional, nonlinear and area-preserving mapping in the variables velocity and time at the instant that the particle collides with the moving wall. The phase space is of mixed type preventing diffusion of the particle to high energy. Successive and therefore rare collisions are shown to have a histogram of frequency which is scaling invariant with respect to the control parameters. The saddle fixed points are studied and shown to be scaling invariant with respect to the control parameters too. © 2012 Elsevier B.V. All rights reserved.
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We present a search for the flavor-changing neutral current decay B-s(0)->phi mu(+)mu(-) using about 0.45 fb(-1) of data collected in p (p) over bar collisions at root s=1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We find an upper limit on the branching ratio of this decay normalized to B-s(0)-> J/psi phi of B(B-s(0)->phi mu(+)mu(-))/B(B-s(0)-> J/psi phi)< 4.4x10(-3) at the 95% C.L. Using the central value of the world average branching fraction of B-s(0)-> J/psi phi, the limit corresponds to B(B-s(0)->phi mu(+)mu(-))< 4.1x10(-6) at the 95% C.L., the most stringent upper bound to date.
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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)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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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).
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We study the production and signatures of doubly charged Higgs bosons (DCHBs) in the process gamma gamma <-> H(--)H(++) at the e(-)e(+) International Linear Collider and CERN Linear Collider, where the intermediate photons are given by the Weizsacker-Willians and laser backscattering distributions.
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Background and Objectives B subgroups are rare and the genetic analysis reported to date has been limited.Materials and Methods Serological and molecular investigations were performed in blood from a B-subgroup donor.Results Red cells did not react with anti-B and anti-AB reagents. However, cells absorbed anti-B. Red cells presented positive reactions with anti-H, and saliva secreted H substance. The molecular study demonstrated a B allele with the substitutions 467C>T, 646T>A, 681G>A, 771C>T, 796C>A, 803G>C, 829G>A and an 0 allele with the sequence of 002.Conclusions It is probable that the presence in exon 7 of some of the 002 substitutions could have weakened the enzymatic activity of the encoded B transferase.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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In the present study, we described a rare association of polycystic liver disease (PCLD) with intracranial meningiomas in patients included on a liver transplant list, focusing on the diagnosis, treatment and possible association with any genetic alterations. Two female patients, aged 39 and 49 years were included on a liver transplant list due to extensive PCLD, with symptoms related to an abdominal compartmental syndrome. Screening for extrahepatic manifestation revealed a right frontal meningioma in the first patient, and a parietal posterior calcified meningioma in the second patient, measuring 1 and 7x3x2 cm in diameter, respectively. Following tumor removal, the histological pattern was compatible with fibrous and transitional meningioma, respectively. Cytogenetic studies conducted following surgery did not reveal any changes in metaphase chromosomes. The postoperative follow-up for the two patients was uneventful, without complications, with the patients remaining on a liver transplant waiting list. We conclude that screening for extrahepatic manifestations of PCLD is mandatory, as certain lesions require treatment prior to liver transplantation. The lack of a genetic or familial association between these two cases show they are likely to have occurred by chance, rather than representing a previously unrecognized association between polycystic liver disease and cranial meningioma.
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This report describes a case of a 49-year-old man with cough, recurrent hemoptysis, and dyspnea during 18 months, presenting with radiological findings of alveolar infiltrate and cystic lesions in left upper lobe. Laboratory studies revealed normocytic hypochromic anemia and normal coagulation tests. C-reactive protein and mucoproteins were negative. Serum protein electrophoresis and complement, urinalysis, serum creatinine, creatinine clearance, and 24-hour urine protein were normal. Tests for antineutrophil cytoplasmic antibodies and anti-glomerular-basement membrane antibodies were negative. Tests for connective tissue diseases were all negative. Histological findings were consistent with those of idiopathic pulmonary hemosiderosis. Radiological findings are discussed.