4,082 research outputs found
On the B and J/Psi Cross Section Measurements at Ua1 and CDF
We analise the implications of the measurement of and inclusive
\pt\ distributions performed in collisions by the UA1 and CDF
experiments.Comment: 16 pages + 8 topdrawer figs included at the end, Latex, IFUP-TH 2/9
Hunting for CDF Multi-Muon "Ghost" Events at Collider and Fixed-Target Experiments
In 2008 the CDF collaboration discovered a large excess of events containing
two or more muons, at least one of which seemed to have been produced outside
the beam pipe. We investigate whether similar "ghost" events could (and should)
have been seen in already completed experiments. The CDF di-muon data can be
reproduced by a simple model where a relatively light X particle undergoes
four-body decay. This model predicts a large number of ghost events in Fermilab
fixed-target experiments E772, E789 and E866, applying the cuts optimized for
analyses of Drell-Yan events. A correct description of events with more than
two muons requires a more complicated model, where two X particles are produced
from a very broad resonance Y. This model can be tested in fixed-target
experiments only if the cut on the angles, or rapidities, of the muons can be
relaxed. Either way, the UA1 experiment at the CERN ppbar collider should have
observed O(100) ghost events.Comment: 15 pages, 9 figure
Electron Cyclotron Radiative Transfer in the Presence of Polarization Scrambling in Wall Reflections
Is There a Significant Excess in Bottom Hadroproduction at the Tevatron?
We discuss the excess in the hadroproduction of B mesons at the Tevatron. We
show that an accurate use of up-to-date information on the B fragmentation
function reduces the observed excess to an acceptable level. Possible
implications for experimental results reporting bottom quark cross sections,
also showing an excess with respect to next-to-leading order theoretical
predictions, are discussed.Comment: 5 pages, Latex, 4 figures. Submitted to Phys. Rev. Let
Low mass lepton pair production in hadron collisions
The hadroproduction of lepton pairs with mass and transverse momentum
can be described in perturbative QCD by the same partonic subprocesses as
prompt photon production. We demonstrate that, like prompt photon production,
lepton pair production is dominated by quark-gluon scattering in the region
. This leads to sensitivity to the gluon density in kinematical
regimes that are accessible both at collider and fixed target experiments while
eliminating the theoretical and experimental uncertainties present in prompt
photon production.Comment: Talk given by M. Klasen at the International Conference on the
Structure and Interactions of the Photon, PHOTON 99, Freiburg i. Brsg.,
Germany, May 23-27, 1999. To be published in the proceedings. 6 pages, 6
postscript figure
Treatment and seroconversion in a cohort of children suffering from recent chronic Chagas infection in Yoro, Honduras
Between 1999-2002, Médécins Sans Frontières-Spain implemented a project seeking to determine the efficacy and safety of benznidazole in the treatment of recent chronic Chagas disease in a cohort of seropositive children in the Yoro Department, Honduras. A total of 24,471 children were screened for Trypanosoma cruzi IgG antibodies through conventional enzyme-linked immunosorbent assays (ELISA) on filter paper. Recombinant ELISA (0.93% seroprevalence) showed 256 initially reactive cases, including 232 confirmed positive cases. Of these, 231 individuals were treated with benznidazole (7.5 mg/kg/day) for 60 days and were followed with a strict weekly medical control and follow-up protocol. At the end of the project, 229 patients were examined by the Honduras Secretariat of Health for post-treatment serological assessments; 88.2% seroconverted after 18 months and 93.9% seroconverted after three years. No differences were found in the seroconversion rates according to age or sex. Most of the side effects of the treatment were minor. These results support the argument that in areas where T. cruzi I is predominant and in areas affected by T. cruzi II, when vector transmission has been interrupted, Chagas disease diagnosis and treatment are feasible, necessary and ethically indisputable
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