1,720,996 research outputs found
The DarkSide veto: muon and neutron detectors
No full textThe existence of dark matter is known because of its gravitational
effects, and although its nature remains undisclosed, there is a growing indication
that the galactic halo could be permeated by weakly interactive massive particles
(WIMPs) with mass of the order of 100 GeV. Direct observation of WIMP-nuclear
collisions in a laboratory detector plays a key role in dark matter searches. However,
it also poses significant challenges, as the expected signals are low in energy and
very rare. DarkSide is a project for direct observation of WIMPs in a liquid argon
time-projection chamber specifically designed to overtake the difficulties of these
challenges. A limiting background for all dark matter detectors is the production in
their active volumes of nuclear recoils from the elastic scattering of radiogenic and
cosmogenic neutrons. To rule out this background, DarkSide-50 is surrounded by
a water tank serving as a Cherenkov detector for muons, and a boron-doped liquid
scintillator acting as an active, high-efficiency neutron detector
The Electronics and Data Acquisition System of the DarkSide Dark Matter Search
No full textThis paper reports on the electronics and data acquisition system
of a dark matter (DM) search using a 50 kg dual-phase, liquid argon time
projection chamber (TPC) which was embedded in water and liquid scintillator
veto detectors (DS-50). If DM is a subatomic particle, a possible candidate is
a Weakly Interacting Massive Particle (WIMP), and the DS-50 experiment is a
direct search for evidence of WIMP-nuclear collisions at the Laboratori Nazionali
del Gran Sasso (LNGS). The light from nuclear excitation in the TPC as a result
of a WIMP-Nuclear collision, is collected by 38 photomultiplier tubes (PMT)
positioned on the top and bottom of the cylindrical TPC cryostat. The two
veto detectors, instrumented with PMT, shield the TPC and tag background
events due to cosmogneic and local radioactivity. All PMT signals from both the
TPC and Veto systems are digitized and their waveforms transferred in parallel
to event building computers running the ARTDAQ software developed at the
Fermi National Laboratory (FNAL). This paper describes the system triggers,
the synchronization of the data flows, and the event building for both the TPC
and Veto
DArKSIDE-50: A view of the first atmospheric argon runDArKside Collaboration
No full textThe DArKside (DS) program aims to detect the so-called WIMPs
(Weakly Interactive Massive Particle) which are considered the best candidates for
Dark Matter. WIMPs elastically scattering would be detected by using a twophase
Time Projection Chamber (TPC) based on argon nuclei target. Thanks to
the properties of the scintillation and ionization signals detected by the TPC it is
possible to discriminate a WIMP-induced signal from one induced by background.
DS-50 started its data taking on November 2013 with atmospheric argon (later with
underground argon depleted in 39Ar.
DarkSide-50: a WIMP search with a two-phase argon TPC
No full textDarkSide-50 is a two phase argon TPC for direct dark matter detection which is installed at the Gran Sasso underground
laboratory, Italy. DarkSide-50 has a 50-kg active volume and will make use of underground argon low 3in9Ar. The
TPC is installed inside an active neutron veto made with boron-loaded high radiopurity liquid scintillator. The neutron
veto is installed inside a 1000 m3 water Cherenkov muon veto. The DarkSide-50 TPC and cryostat are assembled in
two radon-free clean rooms to reduce radioactive contaminants. The overall design aims for a background free exposure
after selection cuts are applied. Theexpected sensitivity for WIMP-nucleon cross section is of the order of 1−045 cm2
for WIMP masses around 100 GeV/c2. The commissioning and performance of the detector are described. Details of
thelow-radioactivity underground argon and other unique features of the projects are reported
First results from the DarkSide-50dark matter experiment at Laboratori Nazionali del Gran Sasso
No full textWe report the first results of DarkSide-50, a direct search for dark matter operating in the underground Laboratori Nazionali del Gran Sasso (LNGS) and searching for the rare nuclear recoils possibly induced by weakly interacting massive particles (WIMPs). The dark matter detector is a Liquid Argon Time Projection Chamber with a (46.4 ±0.7)kgactive mass, operated inside a 30t organic liquid scintillator neutron veto, which is in turn installed at the center of a 1kt water Cherenkov veto for the residual flux of cosmic rays. We report here the null results of a dark matter search for a (1422 ±67)kgdexposure with an atmospheric argon fill. This is the most sensitive dark matter search performed with an argon target, corresponding to a 90% CL upper limit on the WIMP-nucleon spin-independent cross section of 6.1 ×10−44cm2for a WIMP mass of 100Gev/c
The DarkSide Program at LNGS
No full textDarkSide is a direct detection dark matter program at LNGS that is based on two phase depleted argon time projection chambers. A combination of low background construction techniques and active background suppression will give the DarkSide detectors very low and extremely well understood rates of background events. A 10 kg prototype detector is currently being operated at LNGS, while DarkSide-50, the first physics detector in the DarkSide program, is currently being constructed
DarkSide-50: results from first argon run
No full textDarkSide (DS) at Gran Sasso underground laboratory is a direct dark matter search program
based on TPCs with liquid argon from underground sources. The DS-50 TPC, with
50 kg o iquid argon is installed inside active neutron and muon detectors. DS-50 has been
taking data since Nov 2013, collecting more than 10 7 events with atmospheric argon. This
data represents an exposure to the largest background, beta decays of 39 Ar, comparable to
the full 3 y run of DS-50 with underground argon. When analysed with a threshold that
would give a sensitivity in the full run of about 10 − 45 cm2 at a WIMP mass of 100 GeV,
there is no 39 Ar background observed. We present the detector design and performance,
the results from the atmospheric argon run and plans for an upscale to a multi-ton detector
along with its sensitivity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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