1,793 research outputs found
Performance of an Operating High Energy Physics Data Grid: D0SAR-Grid
The D0 experiment at Fermilab's Tevatron will record several petabytes of
data over the next five years in pursuing the goals of understanding nature and
searching for the origin of mass. Computing resources required to analyze these
data far exceed capabilities of any one institution. Moreover, the widely
scattered geographical distribution of D0 collaborators poses further serious
difficulties for optimal use of human and computing resources. These
difficulties will exacerbate in future high energy physics experiments, like
the LHC. The computing grid has long been recognized as a solution to these
problems. This technology is being made a more immediate reality to end users
in D0 by developing a grid in the D0 Southern Analysis Region (D0SAR),
D0SAR-Grid, using all available resources within it and a home-grown local task
manager, McFarm. We will present the architecture in which the D0SAR-Grid is
implemented, the use of technology and the functionality of the grid, and the
experience from operating the grid in simulation, reprocessing and data
analyses for a currently running HEP experiment.Comment: 3 pages, no figures, conference proceedings of DPF04 tal
Development of Large Area GEM Chambers
The High Energy Physics group of the University of Texas at Arlington Physics
Department has been developing Gas Electron Multiplier (GEM) detectors for use
as the sensitive gap detector in digital hadron calorimeters (DHCAL) for the
future International Linear Collider. In this study, two kinds of prototype GEM
detectors have been tested. One has 30x30 cm2 active area double GEM structure
with a 3 mm drift gap, a 1 mm transfer gap and a 1 mm induction gap. The other
one has two 2x2 cm2 GEM foils in the amplifier stage with a 5 mm drift gap, a 2
mm transfer gap and a 1 mm induction gap. We present characteristics of these
detectors obtained using high-energy charged particles, cosmic ray muons and
106Ru and 55Fe radioactive sources. From the 55Fe tests, we observed two
well-separated X-ray emission peaks and measured the chamber gain to be over
6500 with a high voltage of 395 V across each GEM electrode. Both the spectra
from cosmic rays and the 106Ru fit well to Landau distributions as expected
from minimum ionizing particles. We also present the chamber performance after
high dosage exposure to radiation as well as the pressure dependence of the
gain and correction factors. Finally, we discuss the quality test results of
the first set of large scale GEM foils and discuss progress and future plans
for constructing large scale (100cmx100cm) GEM detectors
Application of Large Scale GEM for Digital Hadron Calorimetry
The High Energy Physics group of the University of Texas at Arlington Physics
Department has been developing Gas Electron Multiplier (GEM) detectors for use
as the sensitive gap detector in digital hadron calorimeters (DHCAL) for the
future International Linear Collider. In this study, two kinds of prototype GEM
detectors have been tested. One has 30x30 cm2 active area double GEM structure
with a 3 mm drift gap, a 1 mm transfer gap and a 1 mm induction gap. The other
one has two 2x2 cm2 GEM foils in the amplifier stage with a 5 mm drift gap, a 2
mm transfer gap and a 1 mm induction gap. We present characteristics of these
detectors obtained using high-energy charged particles, cosmic ray muons and
106Ru and 55Fe radioactive sources. From the 55Fe tests, we observed two
well-separated X-ray emission peaks and measured the chamber gain to be over
6500 with a high voltage of 395 V across each GEM electrode. Both the spectra
from cosmic rays and the 106Ru fit well to Landau distributions as expected
from minimum ionizing particles. We also present the chamber performance after
high dosage exposure to radiation as well as the pressure dependence of the
gain and correction factors. Finally, we discuss the quality test results of
the first set of large scale GEM foils and discuss progress and future plans
for constructing large scale (100cmx100cm) GEM detectors
Spatiotemporal Overlap Of Spiny Dogfish (Squalus Acanthias) And Commercial Fisheries In The Northeast Us Shelf Large Marine Ecosystem
Commercial fishermen have argued that localized concentrations of spiny dogfish (Squalus acanthias) in the northeast U.S. shelf large marine ecosystem (NES LME) have impeded their fishing operations when monitoring surveys estimated lower relative abundances. Fishery-dependent and -independent data were analyzed simultaneously to examine whether increased spatial overlap between spiny dogfish and commercial fisheries may explain high catches of this species on fishing grounds. Spatial overlap was quantified between spiny dogfish distribution and commercial fisheries from 1989 to 2009 during autumn and spring in the NES LME. Combined, the sink gillnet (SGN) and otter trawl (OT) fisheries accounted for the majority of spiny dogfish catch (autumn: 85%; spring: 92%), either retained (SGN) or discarded (OT). Centers of spiny dogfish abundance illustrated spatial differences in local density within the NES LME and revealed seasonal differences in spiny dogfish density. Recent increases in spatial overlap indicate that a growing portion of the spiny dogfish stock was available to each fishery over the time series. Availability, estimated as the percentage of spiny dogfish present on fishing grounds, also increased and was generally higher during autumn than spring. Abundance of mature (total length.80 cm) female spiny dogfish was significantly related to availability, but trends were variable between fisheries and seasons. Although recent increases in abundance indicate recovery, research regarding the mechanisms behind these changes may help explain why abundance in the NES LME appears highly variable
Report of the Scientific Council Meeting 01 -15 June 2017
Council met at the Sobey Building, Saint Mary’s University, Halifax, NS, Canada, during 01 – 15 June 2017, to consider the various matters in its Agenda. Representatives attended from Canada, Denmark (in
respect of Faroe Islands and Greenland), the European Union (France, Germany (via WebEx), Portugal, Spain, the United Kingdom and the European Commission), Japan, the Russian Federation and the United States of
America. Observers from the Ecology Action Centre and Dalhousie University were also present. The Executive Secretary, Scientific Council Coordinator and other members of the Secretariat were in attendance.
The Executive Committee met prior to the opening session of the Council to discuss the provisional agenda and plan of work.
The Council was called to order at 1000 hours on 01 June 2017. The provisional agenda was adopted with modification. The Scientific Council Coordinator was appointed the rapporteur.
The Council was informed that the meeting was quorate and authorization had been received by the Executive Secretary for proxy votes from the European Union, Denmark (in respect of Faroe Islands and Greenland),
Iceland, Japan, Republic of Korea, and Norway. The opening session was adjourned at 1200 hours on 01 June 2017. Several sessions were held throughout the
course of the meeting to deal with specific items on the agenda. The Council considered adopted the STACFEN report on 8 June 2017, and the STACPUB, STACFIS and STACREC reports on 15 June 2017.
The concluding session was called to order at 0830 hours on 15 June 2017. The Council considered and adopted the report the Scientific Council Report of this meeting of 01 -15 June
2017. The Chair received approval to leave the report in draft form for about two weeks to allow for minor editing and proof-reading on the usual strict understanding there would be no substantive changes.
The meeting was adjourned at 1430 hours on 15 June 2017. The Reports of the Standing Committees as adopted by the Council are appended as follows: Appendix I - Report
of the Standing Committee on Fisheries Environment (STACFEN), Appendix II - Report of Standing Committee on Publications (STACPUB), Appendix III - Report of Standing Committee on Research Coordination
(STACREC), and Appendix IV - Report of Standing Committee on Fisheries Science (STACFIS). The Agenda, List of Research (SCR) and Summary (SCS) Documents, and List of Representatives, Advisers and
Experts, are given in Appendix V-VII. The Council’s considerations on the Standing Committee Reports, and other matters addressed by the Council
follow in Sections II-XV
Performance of the first prototype of the CALICE scintillator strip electromagnetic calorimeter
A first prototype of a scintillator strip-based electromagnetic calorimeter
was built, consisting of 26 layers of tungsten absorber plates interleaved with
planes of 45x10x3 mm3 plastic scintillator strips. Data were collected using a
positron test beam at DESY with momenta between 1 and 6 GeV/c. The prototype's
performance is presented in terms of the linearity and resolution of the energy
measurement. These results represent an important milestone in the development
of highly granular calorimeters using scintillator strip technology. This
technology is being developed for a future linear collider experiment, aiming
at the precise measurement of jet energies using particle flow techniques
The Time Structure of Hadronic Showers in highly granular Calorimeters with Tungsten and Steel Absorbers
The intrinsic time structure of hadronic showers influences the timing
capability and the required integration time of hadronic calorimeters in
particle physics experiments, and depends on the active medium and on the
absorber of the calorimeter. With the CALICE T3B experiment, a setup of 15
small plastic scintillator tiles read out with Silicon Photomultipliers, the
time structure of showers is measured on a statistical basis with high spatial
and temporal resolution in sampling calorimeters with tungsten and steel
absorbers. The results are compared to GEANT4 (version 9.4 patch 03)
simulations with different hadronic physics models. These comparisons
demonstrate the importance of using high precision treatment of low-energy
neutrons for tungsten absorbers, while an overall good agreement between data
and simulations for all considered models is observed for steel.Comment: 24 pages including author list, 9 figures, published in JINS
Measurement of the t-channel single top quark production cross section
The D0 collaboration reports direct evidence for electroweak production of
single top quarks through the t-channel exchange of a virtual W boson. This is
the first analysis to isolate an individual single top quark production
channel. We select events containing an isolated electron or muon, missing
transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar
collisions at the Fermilab Tevatron Collider. One or two of the jets are
identified as containing a b hadron. We combine three multivariate techniques
optimized for the t-channel process to measure the t- and s-channel cross
sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for
the t-channel and 1.05 +-0.81 pb for the s-channel. The measured t-channel
result is found to have a significance of 4.8 standard deviations and is
consistent with the standard model prediction.Comment: 7 pages, 6 figure
Measurements of differential cross sections of Z/gamma*+jets+X events in proton anti-proton collisions at sqrt{s}=1.96 TeV
We present cross section measurements for Z/gamma*+jets+X production,
differential in the transverse momenta of the three leading jets. The data
sample was collected with the D0 detector at the Fermilab Tevatron proton
anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to
an integrated luminosity of 1 fb-1. Leading and next-to-leading order
perturbative QCD predictions are compared with the measurements, and agreement
is found within the theoretical and experimental uncertainties. We also make
comparisons with the predictions of four event generators. Two
parton-shower-based generators show significant shape and normalization
differences with respect to the data. In contrast, two generators combining
tree-level matrix elements with a parton shower give a reasonable description
of the the shapes observed in data, but the predicted normalizations show
significant differences with respect to the data, reflecting large scale
uncertainties. For specific choices of scales, the normalizations for either
generator can be made to agree with the measurements.Comment: Published in PLB. 11 pages, 3 figure
Measurement of the W boson mass
We present a measurement of the W boson mass in W -> ev decays using 1 fb^-1
of data collected with the D0 detector during Run II of the Fermilab Tevatron
collider. With a sample of 499830 W -> ev candidate events, we measure M_W =
80.401 +- 0.043 GeV. This is the most precise measurement from a single
experiment.Comment: As published in PR
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