Extensive polymorphism and chromosomal characteristics of ribosomal DNA in the characid fish Triportheus venezuelensis (Characiformes, Characidae)

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

IDENTIFYING THE HIGGS-BOSON IN ELECTRON-PHOTON COLLISIONS

We analyze the production and detection of the Higgs boson in the next generation of linear e+e-colliders operating in the egamma mode. In particular, we study the production mechanism e+gamma --> egammagamma --> e + H, where one photon is generated via the laser backscattering mechanism, while the other is radiated via the usual bremsstrahlung process. We show that this is the most important mechanism for Higgs boson production in a 500 GeV egamma collider for M(H) greater than or similar to 140 GeV. We also study the signals and backgrounds for detection of the Higgs boson in the different decay channels bbBAR, W+W-, and ZZ, and suggest kinematical cuts to improve the signature of an intermediate-mass Higgs boson.

CYTOGENETIC STUDIES ON THE SUBFAMILY HYPOPTOPOMATINAE (PISCES, SILURIFORMES, LORICARIIDAE) .3. ANALYSIS OF 7 SPECIES

Cytogenetic studies carried out on nine species belonging to five genera of the subfamily Hypoptopomatinae showed that this group has a relatively constant diploid number, 2n = 54, with only one species having 2n = 72 chromosomes. Nevertheless, the karyotypic formulae, NOR position and C-band pattern are very different among species and sometimes among local populations, with species having undifferentiated sex chromosomes and species having the XX/XY or the ZZ/ZW mechanisms. The population structure of species belonging to the subfamily Hypoptopomatinae suggests that many chromosome rearrangements have been fixed in the different species and populations due to their geographic isolation and these karyotypic differences may be very important today for species definition.

Chromosomal evolution in Gekkonidae. I. Chromosome painting between Gekko and Hemidactylus species reveals phylogenetic relationships within the group

Geckos are a large group of lizards characterized by a rich variety of species, different modes of sex determination and diverse karyotypes. In spite of many unresolved questions on lizards' phylogeny and taxonomy, the karyotypes of most geckos have been studied by conventional cytogenetic methods only. We used flow-sorted chromosome-specific painting probes of Japanese gecko (Gekko japonicus), Mediterranean house gecko (Hemidactylus turcicus) and flat-tailed house gecko (Hemidactylus platyurus) to reveal homologous regions and to study karyotype evolution in seven gecko species (Gekko gecko, G. japonicus, G. ulikovskii, G. vittatus, Hemidactylus frenatus, H. platyurus and H. turcicus). Generally, the karyotypes of geckos were found to be conserved, but we revealed some characteristic rearrangements including both fissions and fusions in Hemidactylus. The karyotype of H. platyurus contained a heteromorphic pair in all female individuals, where one of the homologues had a terminal DAPI-negative and C-positive heterochromatic block that might indicate a putative sex chromosome. Among two male individuals studied, only one carried such a polymorphism, and the second one had none, suggesting a possible ZZ/ZW sex determination in some populations of this species. We found that all Gekko species have retained the putative ancestral karyotype, whilst the fission of the largest ancestral chromosome occurred in the ancestor of modern Hemidactylus species. Three common fissions occurred in the ancestor of Mediterranean house and flat-tailed house geckos, suggesting their sister group relationships. PCR-assisted mapping on flow-sorted chromosome libraries with conserved DMRT1 gene primers in G. japonicus indicates the localization of DMRT1 gene on chromosome 6.

Efeito da seleção quanto ao peso corporal nas características reprodutivas em linhagens de frangos de corte

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Strongly interacting vector bosons at the CERN LHC: Quartic anomalous couplings

We analyze the potential of the CERN Large Hadron Collider to study anomalous quartic vector-boson interactions through the production of vector-boson pairs accompanied by jets. In the framework of SU(2) L⊗U(1) Y chiral Lagrangians, we examine all effective operators of order p 4 that lead to new four-gauge-boson interactions but do not alter trilinear vertices. In our analyses, we perform the full tree-level calculation of the processes leading to two jets plus vector-boson pairs, W +W -,W ±W ±,W ±Z, or ZZ, taking properly into account the interference between the standard model and the anomalous contributions. We obtain the bounds that can be placed on the anomalous quartic interactions and we study the strategies to distinguish the possible new couplings. ©1998 The American Physical Society.

Morphologically differentiated sex chromosomes in neotropical freshwater fish

A general survey of the occurrence of morphologically differentiated sex chromosomes in the neotropical freshwater fishes is presented. The total number of 32 occurrences involving simple XX-XY and ZZ-ZW, and multiple X1X2Y, XY1Y2 and ZW1W2 sex chromosome systems is described, with comments on the aspects of sex chromosome evolution in this fish fauna. The occurrence of different sex chromosome systems in related species of the same genus, or in different populations of the same nominal species, involving male and sometimes female heterogamety, and differences in the molecular composition of sex-linked heterochromatin, are considered as indicative of the early stage of sex chromosomes evolution in fish.

Search for the standard model Higgs boson in ZH→ + -bb̄ production with the D0 detector in 9.7fb -1 of pp̄ collisions at √s=1.96TeV

We present a search for the standard model (SM) Higgs boson produced in association with a Z boson in 9.7fb -1 of pp̄ collisions collected with the D0 detector at the Fermilab Tevatron Collider at √s=1.96TeV. Selected events contain one reconstructed Z→e +e - or Z→μ +μ - candidate and at least two jets, including at least one jet identified as likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production in the same final state. It is found to be consistent with its SM prediction. We set upper limits on the ZH production cross section times branching ratio for H→bb̄ at the 95% C.L. for Higgs boson masses 90≤M H≤150GeV. The observed (expected) limit for M H=125GeV is 7.1 (5.1) times the SM cross section. © 2012 American Physical Society.

Cytogenetic analysis in Thoracocharax stellatus (Kner, 1858) (Characiformes, Gasteropelecidae) from Paraguay river basin, Mato Grosso, Brazil

Thoracocharax stellatus (Characiformes, Gasteropelecidae) is a small Neotropical species of fish, widely distributed in several rivers of South America. Evidence for karyotype heteromorphysm in populations from different geographical regions has been reported for this species. In this way, populations of T. stellatus from the Paraguay River basin were cytogenetically characterized and the results were compared with other studies performed in the same species but from different basins. The results showed a diploid number of 2n = 54 for T. stellatus, with chromosomes arranged in 6 metacentric (m), 6 submetacentric (sm), 2 subtelocentric (st) and 40 acrocentric (a), for both sexes, with a simple Nucleolus Organiser Region (NOR) system reported by the techniques of silver nitrate impregnation and fluorescent in situ hybridisation (FISH) using 18S rDNA sequences as probe. The distribution of constitutive heterochromatin, observed by the C-band technique and Chromomycin A3 staining showed great similarity among the analyzed populations and consists mainly of discrete blocks in the pericentromeric and telomeric regions of most chromosomes. The presence of female heterogamety was alsoobserved indicating a ZZ/ZW system with W chromosome almost totally heterochromatic. The results also show cytogenetic diversity of the group and are useful to understand the mechanisms of karyotype evolution of the family. © Edson Lourenço da Silva et al.

Chromosome painting of Z and W sex chromosomes in Characidium (Characiformes, Crenuchidae)

Some species of the genus Characidium have heteromorphic ZZ/ZW sex chromosomes with a totally heterochromatic W chromosome. Methods for chromosome microdissection associated with chromosome painting have become important tools for cytogenetic studies in Neotropical fish. In Characidium cf. fasciatum, the Z chromosome contains a pericentromeric heterochromatin block, whereas the W chromosome is completely heterochromatic. Therefore, a probe was produced from the W chromosome through microdissection and degenerate oligonucleotide-primed polymerase chain reaction amplification. FISH was performed using the W probe on the chromosomes of specimens of this species. This revealed expressive marks in the pericentromeric region of the Z chromosome as well as a completely painted W chromosome. When applying the same probe on chromosome preparations of C. cf. gomesi and Characidium sp., a pattern similar to C. cf. fasciatum was found, while C. cf. zebra, C. cf. lagosantense and Crenuchus spilurus species showed no hybridization signals. Structural changes in the chromosomes of an ancestral sexual system in the group that includes the species C. cf. gomesi, C. cf. fasciatum and Characidium sp., could have contributed to the process of speciation and could represent a causal mechanism of chromosomal diversification in this group. The heterochromatinization process possibly began in homomorphic and homologous chromosomes of an ancestral form, and this process could have given rise to the current patterns found in the species with sex chromosome heteromorphism. © 2013 Springer Science+Business Media Dordrecht.

Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs

A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 fb-1, collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or μ pairs, is 126.2±0.6(stat) ±0.2(syst) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis. © 2013 CERN. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Search for a standard-model-like Higgs boson with a mass in the range 145 to 1000 GeV at the LHC

A search for a standard-model-like Higgs boson in the H→WW and H→ZZ decay channels is reported, for Higgs boson masses in the range 145

Searches for Higgs bosons in pp collisions at s=7 and 8 TeV in the context of four-generation and fermiophobic models

Searches are reported for Higgs bosons in the context of either the standard model extended to include a fourth generation of fermions (SM4) with masses of up to 600 GeV or fermiophobic models. For the former, results from three decay modes (ττ, WW, and ZZ) are combined, whilst for the latter the diphoton decay is exploited. The analysed proton-proton collision data correspond to integrated luminosities of up to 5.1 fb-1 at 7 TeV and up to 5.3 fb-1 at 8 TeV. The observed results exclude the SM4 Higgs boson in the mass range 110-600 GeV at 99% confidence level (CL), and in the mass range 110-560 GeV at 99.9% CL. A fermiophobic Higgs boson is excluded in the mass range 110-147 GeV at 95% CL, and in the range 110-133 GeV at 99% CL. The recently observed boson with a mass near 125 GeV is not consistent with either an SM4 or a fermiophobic Higgs boson. © 2013 CERN.

Observation of a new boson with mass near 125 GeV in pp collisions at √=7 and 8 TeV

A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb-1 at √=7 TeV, and up to 5.3 fb-1 at √ s=8 TeV. The results for five Higgs boson decay modes γγ, ZZ, WW, ττ, and bb, which show a combined local significance of 5 standard deviations near 125 GeV, are reviewed. A fit to the invariant mass of the two high resolution channels, γγ and ZZ → 4ℓ, gives a mass estimate of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The measurements are interpreted in the context of the standard model Lagrangian for the scalar Higgs field interacting with fermions and vector bosons. The measured values of the corresponding couplings are compared to the standard model predictions. The hypothesis of custodial symmetry is tested through the measurement of the ratio of the couplings to the W and Z bosons. All the results are consistent, within their uncertainties, with the expectations for a standard model Higgs boson. [Figure not available: see fulltext.] © 2013 CERN for the benefit of the CMS collaboration.

Search for exotic resonances in diboson final states with the CMS detector at the LHC

The results of searches for new resonances decaying to a pair of massive vector bosons (WW, WZ, ZZ) are presented. All searches are performed using 5.0 fb-1 of proton-proton collisions, at TeV of center of mass energy, collected by the Compact Muon Solenoid detector at the Large Hadron Collider. No significant excess compared to the standard model background expectation is observed, and upper limits at 95% confidence level are set on the production cross section times the branching fraction of hypothetical particles decaying to a pair of vector bosons. The results are interpreted in the context of several benchmark models, such as the Randall-Sundrum gravitons, the Sequential Standard Model W′, and Technicolor. Graviton resonances in the Randall-Sundrum model with masses smaller than 940 GeV/c2, for coupling parameter k/MPl = 0.05 are excluded. Bulk (ADPS) Randall-Sundrum gravitons with masses smaller than 610 GeV/c2 are excluded, for k/MPl = 0.05. Sequential Standard Model W′ with masses smaller than 1143 GeV/c2 are excluded, as well as ρTC in the 167-687 GeV/c2 mass range, in Low Scale Technicolor models with M(πTC) = 3/4 M(ρTC) - 25 GeV/c2. © 2013 IOP Publishing Ltd.