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Distributions of brominated organic compounds in the troposphere and lower stratosphere
A comprehensive suite of brominated organic compounds was measured from whole air samples collected during the 1996 NASA Stratospheric Tracers of Atmospheric Transport aircraft campaign and the 1996 NASA Global Tropospheric Experiment Pacific Exploratory Mission-Tropics aircraft campaign. Measurements of individual species and total organic bromine were utilized to describe latitudinal and vertical distributions in the troposphere and lower stratosphere, fractional contributions to total organic bromine by individual species, fractional dissociation of the long-lived species relative to CFC-11, and the Ozone Depletion Potential of the halons and CH3Br. Spatial differences in the various organic brominated compounds were related to their respective sources and chemical lifetimes. The difference between tropospheric mixing ratios in the Northern and Southern Hemispheres for halons was approximately equivalent to their annual tropospheric growth rates, while the interhemispheric ratio of CH3Br was 1.18. The shorter-lived brominated organic species showed larger tropospheric mixing ratios in the tropics relative to midlatitudes, which may reflect marine biogenic sources. Significant vertical gradients in the troposphere were observed for the short-lived species with upper troposphere values 40-70% of the lower troposphere values. Much smaller vertical gradients (3-14%) were observed for CH3Br, and no significant vertical gradients were observed for the halons. Above the tropopause, the decrease in organic bromine compounds was found to have some seasonal and latitudinal differences. The combined losses of the individual compounds resulted in a loss of total organic bromine between the tropopause and 20 km of 38-40% in the tropics and 75-85% in midlatitudes. The fractional dissociation of the halons and CH3Br relative to CFC-11 showed latitudinal differences, with larger values in the tropics. Copyright 1999 by the American Geophysical Union
The Central Laser Facility at the Pierre Auger Observatory
The Central Laser Facility is located near the middle of the Pierre Auger
Observatory in Argentina. It features a UV laser and optics that direct a beam
of calibrated pulsed light into the sky. Light scattered from this beam
produces tracks in the Auger optical detectors which normally record nitrogen
fluorescence tracks from cosmic ray air showers. The Central Laser Facility
provides a "test beam" to investigate properties of the atmosphere and the
fluorescence detectors. The laser can send light via optical fiber
simultaneously to the nearest surface detector tank for hybrid timing analyses.
We describe the facility and show some examples of its many uses.Comment: 4 pages, 5 figures, submitted to 29th ICRC Pune Indi
Performance of a small size telescope (SST-1M) camera for gamma-ray astronomy with the Cherenkov Telescope Array
The foreseen implementations of the Small Size Telescopes (SST) in CTA will
provide unique insights into the highest energy gamma rays offering fundamental
means to discover and under- stand the sources populating the Galaxy and our
local neighborhood. Aiming at such a goal, the SST-1M is one of the three
different implementations that are being prototyped and tested for CTA. SST-1M
is a Davies-Cotton single mirror telescope equipped with a unique camera
technology based on SiPMs with demonstrated advantages over classical
photomultipliers in terms of duty-cycle. In this contribution, we describe the
telescope components, the camera, and the trigger and readout system. The
results of the commissioning of the camera using a dedicated test setup are
then presented. The performances of the camera first prototype in terms of
expected trigger rates and trigger efficiencies for different night-sky
background conditions are presented, and the camera response is compared to
end-to-end simulations.Comment: All CTA contributions at arXiv:1709.0348
Development of a strategy for calibrating the novel SiPM camera of the SST-1M telescope proposed for the Cherenkov Telescope Array
CTA will comprise a sub-array of up to 70 small size telescopes (SSTs) at the
southern array. The SST-1M project, a 4 m-diameter Davies Cotton telescope with
9 degrees FoV and a 1296 pixels SiPM camera, is designed to meet the
requirements of the next generation ground based gamma-ray observatory CTA in
the energy range above 3 TeV. Silicon photomultipliers (SiPM) cameras of
gamma-ray telescopes can achieve good performance even during high night sky
background conditions. Defining a fully automated calibration strategy of SiPM
cameras is of great importance for large scale production validation and online
calibration. The SST-1M sub-consortium developed a software compatible with CTA
pipeline software (CTApipe). The calibration of the SST-1M camera is based on
the Camera Test Setup (CTS), a set of LED boards mounted in front of the
camera. The CTS LEDs are operated in pulsed or continuous mode to emulate
signal and night sky background respectively. Continuous and pulsed light data
analysis allows us to extract single pixel calibration parameters to be used
during CTA operation.Comment: All CTA contributions at arXiv:1709.0348
Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector
Inclusive J/psi production in photon-photon collisions has been observed at
LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X
is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an
integrated luminosity of 617 pb^{-1}, yielding a cross-section of
sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the
event shapes of different types of gamma gamma processes in the PYTHIA program,
we conclude that (74 +/- 22)% of the observed J/psi events are due to
`resolved' photons, the dominant contribution of which is most probably due to
the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.
Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance
This paper presents DELPHI measurements and interpretations of
cross-sections, forward-backward asymmetries, and angular distributions, for
the e+e- -> ffbar process for centre-of-mass energies above the Z resonance,
from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are
consistent with the predictions of the Standard Model and are used to study a
variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering
and several models which include physics beyond the Standard Model: the
exchange of Z' bosons, contact interactions between fermions, the exchange of
gravitons in large extra dimensions and the exchange of sneutrino in R-parity
violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.
A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events
Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the
Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy
and momentum constraint methods. The results are expressed as deviations from
the nominal LEP centre-of-mass energy, measured using other techniques. The
results are found to be compatible with the LEP Energy Working Group estimates
for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
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