1,484 research outputs found
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
Disentangling Dark Matter Dynamics with Directional Detection
Inelastic dark matter reconciles the DAMA anomaly with other null direct
detection experiments and points to a non-minimal structure in the dark matter
sector. In addition to the dominant inelastic interaction, dark matter
scattering may have a subdominant elastic component. If these elastic
interactions are suppressed at low momentum transfer, they will have similar
nuclear recoil spectra to inelastic scattering events. While upcoming direct
detection experiments will see strong signals from such models, they may not be
able to unambiguously determine the presence of the subdominant elastic
scattering from the recoil spectra alone. We show that directional detection
experiments can separate elastic and inelastic scattering events and discover
the underlying dynamics of dark matter models.Comment: 7 pages, 5 figures, references and figures update
Models of Holographic superconductivity
We construct general models for holographic superconductivity parametrized by
three couplings which are functions of a real scalar field and show that under
general assumptions they describe superconducting phase transitions. While some
features are universal and model independent, important aspects of the quantum
critical behavior strongly depend on the choice of couplings, such as the order
of the phase transition and critical exponents of second-order phase
transitions. In particular, we study a one-parameter model where the phase
transition changes from second to first order above some critical value of the
parameter and a model with tunable critical exponents.Comment: 15 pages, 6 figure
Local quasiparticle density of states of superconducting SmFeAsOF single crystals: Evidence for spin-mediated pairing
We probe the local quasiparticles density-of-states in micron-sized
SmFeAsOF single-crystals by means of Scanning Tunnelling
Spectroscopy. Spectral features resemble those of cuprates, particularly a
dip-hump-like structure developed at energies larger than the gap that can be
ascribed to the coupling of quasiparticles to a collective mode, quite likely a
resonant spin mode. The energy of the collective mode revealed in our study
decreases when the pairing strength increases. Our findings support
spin-fluctuation-mediated pairing in pnictides.Comment: 11 pages, 4 figure
Discrete dark matter
We propose a new motivation for the stability of dark matter (DM). We suggest
that the same non-abelian discrete flavor symmetry which accounts for the
observed pattern of neutrino oscillations, spontaneously breaks to a Z2
subgroup which renders DM stable. The simplest scheme leads to a scalar doublet
DM potentially detectable in nuclear recoil experiments, inverse neutrino mass
hierarchy, hence a neutrinoless double beta decay rate accessible to upcoming
searches, while reactor angle equal to zero gives no CP violation in neutrino
oscillations.Comment: minor changes to match version accepted in PRD, one reference adde
Gator: a low-background counting facility at the Gran Sasso Underground Laboratory
A low-background germanium spectrometer has been installed and is being
operated in an ultra-low background shield (the Gator facility) at the Gran
Sasso underground laboratory in Italy (LNGS). With an integrated rate of ~0.16
events/min in the energy range between 100-2700 keV, the background is
comparable to those of the world's most sensitive germanium detectors. After a
detailed description of the facility, its background sources as well as the
calibration and efficiency measurements are introduced. Two independent
analysis methods are described and compared using examples from selected sample
measurements. The Gator facility is used to screen materials for XENON, GERDA,
and in the context of next-generation astroparticle physics facilities such as
DARWIN.Comment: 14 pages, 6 figures, published versio
Study of nuclear recoils in liquid argon with monoenergetic neutrons
For the development of liquid argon dark matter detectors we assembled a
setup in the laboratory to scatter neutrons on a small liquid argon target. The
neutrons are produced mono-energetically (E_kin=2.45 MeV) by nuclear fusion in
a deuterium plasma and are collimated onto a 3" liquid argon cell operating in
single-phase mode (zero electric field). Organic liquid scintillators are used
to tag scattered neutrons and to provide a time-of-flight measurement. The
setup is designed to study light pulse shapes and scintillation yields from
nuclear and electronic recoils as well as from {\alpha}-particles at working
points relevant to dark matter searches. Liquid argon offers the possibility to
scrutinise scintillation yields in noble liquids with respect to the
populations of the two fundamental excimer states. Here we present experimental
methods and first results from recent data towards such studies.Comment: 9 pages, 8 figures, proceedings of TAUP 2011, to be published in
Journal of Physics: Conference Series (JCPS
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