373 research outputs found
Metazoários Parasitos De Lambari Astyanax Altiparanae, Coletados Do Rio Do Peixe, São Paulo, Sudeste Do Brasil
In March 2010, 44 specimens of Astyanax altiparanae Garutti & Britski, 2000, commonly known as “lambari do rabo amarelo”, collected from the Peixe river in the state of São Paulo, Brazil were analyzed. Out of these 44 fishes, 38 had at least one species of metazoan parasite. Fifteen metazoan parasites species were collected and identified: Urocleidoides trinidadensis, Diaphorocleidus kabatai, Diaphorocleidus orthodusus, Diaphorocleidus sp., Urocleidoides sp., Trinibaculum altiparanae, Gyrodactylus sp., Jainus hexops, Contracaecum sp., Procamallanus (Spirocamallanus) inopinatus, Vaigamus sp., Amplexibranchius bryconis, Ergasilus sp., Zonocotyloides haroltravassossi and Henneguya sp. Six species of parasites presented a prevalence of over 10%. Weight and length of fishes didn’t influence the parasitism. All parasites presented an aggregated distribution. The parasite community of Astyanax altiparanae from the Peixe river was characterized as having high richness and low uniformity. © 2016, Universidade Federal de Santa Maria. All rights reserved.46587688
The Constraint on FCNC Coupling of the Top Quark with a Gluon from ep Collisions
Using the constraint on the single top production cross-section obtained at
the HERA collider, , we evaluate an upper limit on
oupling constant of the anomalous top quark interaction with a gluon via
flavor-changing neutral current: ,
BRComment: Latex, 3 figures, missed references were adde
Sneutrino Identification in Lepton Pair Production at ILC with Polarized Beams
Numerous non-standard dynamics are described by contact-like effective
interactions that can manifest themselves in electron-positron collisions only
through deviations of the observables (cross sections, asymmetries) from the
Standard Model predictions. If such a deviation were observed, it would be
important to identify the actual source among the possible non-standard
interactions as many different new physics scenarios may lead to very similar
experimental signatures. We study the possibility of uniquely identifying the
indirect effects of s-channel sneutrino exchange, as predicted by
supersymmetric theories with R-parity violation, against other new physics
scenarios in high-energy e^+e^- annihilation into lepton pairs at the
International Linear Collider. These competitive models are interactions based
on gravity in large and in TeV-scale extra dimensions, anomalous gauge
couplings, Z' vector bosons and compositeness-inspired four-fermion contact
interactions. To evaluate the identification reach on sneutrino exchange, we
use as basic observable a double polarization asymmetry, that is particularly
suitable to directly test for such s-channel sneutrino exchange effects in the
data analysis. The availability of both beams being polarized plays a crucial
role in identifying the new physics scenario.Comment: 10 pages, 3 figure
Discriminating Z' from anomalous trilinear gauge coupling signatures in e+e- \to W+W- at ILC with polarized beams
New heavy neutral gauge bosons Z' are predicted by many models of physics
beyond the Standard Model. It is quite possible that Z's are heavy enough to
lie beyond the discovery reach of the CERN Large Hadron Collider LHC, in which
case only indirect signatures of Z' exchanges may emerge at future colliders,
through deviations of the measured cross sections from the Standard Model
predictions. We discuss in this context the foreseeable sensitivity to Z's of
W^\pm-pair production cross sections at the e^+e^- International Linear
Collider (ILC), especially as regards the potential of distinguishing
observable effects of the Z' from analogous ones due to competitor models with
anomalous trilinear gauge couplings (AGC) that can lead to the same or similar
new physics experimental signatures at the ILC. The sensitivity of the ILC for
probing the Z-Z' mixing and its capability to distinguish these two new physics
scenarios is substantially enhanced when the polarization of the initial beams
and the produced W^\pm bosons are considered. A model independent analysis of
the Z' effects in the process e^+e^- \to W^+W^- allows to differentiate the
full class of vector Z' models from those with anomalous trilinear gauge
couplings, with one notable exception: the sequential SM (SSM)-like models can
in this process not be distinguished from anomalous gauge couplings. Results of
model dependent analysis of a specific Z' are expressed in terms of discovery
and identification reaches on the Z-Z' mixing angle and the Z' mass.Comment: 33 pages; v2: version to appear in EPJ
Associated production of light gravitinos in e^+e^- and e^-\gamma collisions
Light gravitino productions in association with a neutralino (selectron) in
e^+e^- (e^-\gamma) collisions are restudied in a scenario that the lightest
supersymmetric particle is a gravitino and the produced neutralino (selectron)
promptly decays into a photon (electron) and a gravitino. We explicitly give
the helicity amplitudes for the production processes by using the effective
goldstino interaction Lagrangian, and present the cross sections with different
collision energies and mass spectra. We also examine selection efficiencies by
kinematical cuts and beam polarizations for the signal and background
processes, and show that the energy and angular distributions of the photon
(electron) can explore the mass of the t-channel exchange particle as well as
the mass of the decaying particle at a future e^+e^- (e^-\gamma) collider.Comment: 12 pages, 12 figures, 4 tables; references added, version to appear
in EPJ
Colour reconnections in Herwig++
We describe the implementation details of the colour reconnection model in
the event generator Herwig++. We study the impact on final-state observables in
detail and confirm the model idea from colour preconfinement on the basis of
studies within the cluster hadronization model. Moreover, we show that the
description of minimum bias and underlying event data at the LHC is improved
with this model and present results of a tune to available data.Comment: 19 pages, 21 figures, 2 tables. Matches with published versio
On the mechanisms of heavy-quarkonium hadroproduction
We discuss the various mechanisms potentially at work in hadroproduction of
heavy quarkonia in the light of computations of higher-order QCD corrections
both in the Colour-Singlet (CS) and Colour-Octet (CO) channels and the
inclusion of the contribution arising from the s-channel cut in the CS channel.
We also discuss new observables meant to better discriminate between these
different mechanisms.Comment: Invited review talk at 3rd International Conference On Hard And
Electromagnetic Probes Of High-Energy Nuclear Collisions (HP2008), 8-14 June
2008, Illa da Toxa, Galicia, Spain. 11 pages, 21 figures, LaTeX, uses
svjour.cls and svepj.clo (included
Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s=13TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2fb−1 of proton–proton collisions at a centre-of-mass energy of s=13TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:σtt¯=818±8(stat)±27(syst)±19(lumi)±12(beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
Determination of QCD condensates from tau-decay data
We have used the latest data from the ALEPH Collaboration to extract values
for QCD condensates up to dimension d=12 in the V-A channel and up to dimension
d=8 in the V, A and V+A channels. Performing 2- and 3-parameter fits, we obtain
new results for the correlations of condensates. The results are consistent
among themselves and agree with most of the previous results found in the
literature.Comment: 22 page
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