The lead-glass electromagnetic calorimeter for the SELEX experiment Balatz, M.Y.; Cooper, P.S.; Davidenko, G.V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2005, Letnik:
545, Številka:
1
Journal Article
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A large-acceptance, highly segmented electromagnetic lead-glass calorimeter for Experiment E781 (SELEX) at Fermi National Acceleration Laboratory was designed and built. This detector has been used ...to reconstruct photons and electrons with energies ranging from a few GeV up to 500
GeV in the collisions of the 600
GeV
Σ
-
hyperons,
π
mesons and protons with the target nucleons. The design, calibration and performance of the calorimeter are described. Energy resolution and position resolution are assessed using both calibration electron beams and
π
0
mesons reconstructed in 600
GeV hadron–hadron interactions. The performance of the calorimeter in selecting resonant states that involve photons is demonstrated.
We report the first observation of the Cabibbo-suppressed charm baryon decay Xi(+)(c)-->pK(-)pi(+). We observe 150+/-22+/-5 events for the signal. The data were accumulated using the SELEX ...spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma(-) beam. The branching fractions of the decay relative to the Cabibbo-favored Xi(+)(c)-->Sigma+K-pi(+) and Xi(+)(c)-->Xi(-)pi(+)pi(+) are measured to be B(Xi(+)(c)-->pK(-)pi(+))/B(Xi(+)(c)-->Sigma+K-pi(+)) = 0.22+/-0. 06+/-0.03 and B(Xi(+)(c)-->pK(-)pi(+))/B(Xi(+)(c)-->Xi(-)pi(+)pi(+)) = 0.20+/-0.04+/-0.02, respectively.
We observe a signal for the doubly charmed baryon Xi(+)(cc) in the charged decay mode Xi(+)(cc)-->Lambda(+)(c)K-pi(+) in data from SELEX, the charm hadroproduction experiment at Fermilab. We observe ...an excess of 15.9 events over an expected background of 6.1+/-0.5 events, a statistical significance of 6.3sigma. The observed mass of this state is 3519+/-1 MeV/c(2). The Gaussian mass width of this state is 3 MeV/c(2), consistent with resolution; its lifetime is less than 33 fs at 90% confidence.
The neurotoxic effect of exposure of rat cerebellar granule cells to glutamate (100 microM) is to a large extent prevented by incubation of neurons not only with micromolar, but even with nanomolar ...concentrations of gangliosides GM1, GD1b, and GT1b. GM1 was also shown to decrease significantly the per cent of dead neurons in culture after induction of lipid peroxidation. Exposure to glutamate was found to cause a significant decrease of the activity of Na+, K+-ATP-ase in rat brain cortex synaptosomes, but superoxide dismutase, alpha-tocopherol, or 10-100 nM GM1 practically prevented its action. Other data showing the ability of gangliosides to inhibit the intensification of free radical reactions by glutamate (based on the estimation of methemoglobin formation, SH group content, etc.) have been obtained. The results suggest that gangliosides are able to decrease the glutamate-induced activation of free radical reactions in nerve cells. This effect appears to contribute to their protective action against glutamate neurotoxicity.
A large-scale prototype of the PHOS electromagnetic spectrometer, which is part of the ALICE detector, has been built and tested. This prototype has 256 detector channels and is operated at −25
°C. ...Each detector channel is a lead-tungstate crystal coupled to an Avalanche Photo-Diode with a low-noise preamplifier. The prototype includes a 16×16 crystal matrix, photo-detectors, analog and digital electronics, a thermo-stabilized cooling system, a light-emitting diode monitoring system, and a charged-particle detector acting as veto counter. Results of measurements using electron and hadron beams of the CERN PS and SPS accelerators are discussed, and the performance of the prototype is evaluated.
We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for Λ̄c− compared to Λc+ as a function of xF, and on pt2 distributions for Λc+. These data were measured in the ...same apparatus using incident π−, Σ− beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF⩾0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Λc formation, as suggested by the leading quark picture.
Low doses (0.1–0.3
μg
ml
per 10
6 cells) of the lipopolysaccharide toxin (LPS) from
Salmonella typhimurium were shown to increase (after an 18 h incubation) the intracellular content of free ...cholesterol (CH), esterified cholesterol (EC) and triglycerides (TG) by 30–40% in the primary culture of rabbit hepatocytes. A similar increase was found for the incorporation of
14Cacetate into these lipids. The concentration of lipids in cultural medium, under these conditions, was also augmented: by 30–40% for CH; by 50–60% for TG and by 60–80% for EC. Higher doses (up to 50
μg
ml
) of LPS hardly affected the lipid content in hepatocytes but strongly (by two-fold) inhibited the secretion of lipids. It is suggested that in vivo low concentrations of LPS in bloodstream (in the absence of conspicuous pathology) might induce hyperlipidemia directly influencing on hepatic cells, while, under the higher concentrations of LPS, hyperlipidemia caused by cachectin (or tumor necrosis factor) is probably observed.
Lipopolysaccharide toxin; Hyperlipidemia; (Rabbit hepatocyte)
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