332 research outputs found
The EDELWEISS experiment and Dark Matter Direct Detection
This mini-review first introduces the motivations for Dark Matter Searches.
The experimental aspect of the direct detection of Weakly Interactive Massive
Particles (WIMPs) is described, detailing its principle and presenting some
experiments with their recent results. The EDELWEISS experiment and its results
are discussed in more details before concluding with the future direct
detection experiments.Comment: 9 pages, 6 figures, 2 tables, to appear in Proceedings of the Moriond
Electroweak 2003 conferenc
Status of the EDELWEISS-II experiment
EDELWEISS is a direct dark matter search experiment situated in the low
radioactivity environment of the Modane Underground Laboratory. The experiment
uses Ge detectors at very low temperature in order to identify eventual rare
nuclear recoils induced by elastic scattering of WIMPs from our Galactic halo.
We present results of the commissioning of the second phase of the experiment,
involving more than 7 kg of Ge, that has been completed in 2007. We describe
two new types of detectors with active rejection of events due to surface
contamination. This active rejection is required in order to achieve the
physics goals of 10-8 pb cross-section measurement for the current phase
DAMA detection claim is still compatible with all other DM searches
We show that the annual modulation signal observed by DAMA can be reconciled
with all other negative results from dark matter searches with a conventional
halo model for particle masses around 5 to 9 GeV. We also show which particular
dark matter stream could produce the DAMA signal.Comment: Talk given at TAUP2005, Sept. 10-14 2005, Zaragoza (Spain). 3 pages,
4 figure
On the direct search for spin-dependent WIMP interactions
We examine the current directions in the search for spin-dependent dark
matter. We discover that, with few exceptions, the search activity is
concentrated towards constraints on the WIMP-neutron spin coupling, with
significantly less impact in the WIMP-proton sector. We review the situation of
those experiments with WIMP-proton spin sensitivity, toward identifying those
capable of reestablishing the balance.Comment: 7 pages, 4 figure
Electron - nuclear recoil discrimination by pulse shape analysis
In the framework of the ``ULTIMA'' project, we use ultra cold superfluid 3He
bolometers for the direct detection of single particle events, aimed for a
future use as a dark matter detector. One parameter of the pulse shape observed
after such an event is the thermalization time constant. Until now it was
believed that this parameter only depends on geometrical factors and superfluid
3He properties, and that it is independent of the nature of the incident
particles. In this report we show new results which demonstrate that a
difference for muon- and neutron events, as well as events simulated by heater
pulses exist. The possibility to use this difference for event discrimination
in a future dark matter detector will be discussed.Comment: Proseedings of QFS 2007, Kazan, Russia; 8 pages, 4 figures. Submited
to J. Low Temp. Phy
What it takes to measure a fundamental difference between dark matter and baryons: the halo velocity anisotropy
Numerous ongoing experiments aim at detecting WIMP dark matter particles from
the galactic halo directly through WIMP-nucleon interactions. Once such a
detection is established a confirmation of the galactic origin of the signal is
needed. This requires a direction-sensitive detector. We show that such a
detector can measure the velocity anisotropy beta of the galactic halo.
Cosmological N-body simulations predict the dark matter anisotropy to be
nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a
nonzero beta would be strong proof of the fundamental difference between dark
and baryonic matter. We estimate the sensitivity for various detector
configurations using Monte Carlo methods and we show that the strongest signal
is found in the relatively few high recoil energy events. Measuring beta to the
precision of ~0.03 will require detecting more than 10^4 WIMP events with
nuclear recoil energies greater than 100 keV for a WIMP mass of 100 GeV and a
32S target. This number corresponds to ~10^6 events at all energies. We discuss
variations with respect to input parameters and we show that our method is
robust to the presence of backgrounds and discuss the possible improved
sensitivity for an energy-sensitive detector.Comment: 15 pages, 8 figures, accepted by JCAP. Matches accepted versio
High-Resolution Genetics Identifies the Lipid Transfer Protein Sec14p as Target for Antifungal Ergolines.
Invasive infections by fungal pathogens cause more deaths than malaria worldwide. We found the ergoline compound NGx04 in an antifungal screen, with selectivity over mammalian cells. High-resolution chemogenomics identified the lipid transfer protein Sec14p as the target of NGx04 and compound-resistant mutations in Sec14p define compound-target interactions in the substrate binding pocket of the protein. Beyond its essential lipid transfer function in a variety of pathogenic fungi, Sec14p is also involved in secretion of virulence determinants essential for the pathogenicity of fungi such as Cryptococcus neoformans, making Sec14p an attractive antifungal target. Consistent with this dual function, we demonstrate that NGx04 inhibits the growth of two clinical isolates of C. neoformans and that NGx04-related compounds have equal and even higher potency against C. neoformans. Furthermore NGx04 analogues showed fungicidal activity against a fluconazole resistant C. neoformans strain. In summary, we present genetic evidence that NGx04 inhibits fungal Sec14p and initial data supporting NGx04 as a novel antifungal starting point
Identification of backgrounds in the EDELWEISS-I dark matter search experiment
This paper presents our interpretation and understanding of the different
backgrounds in the EDELWEISS-I data sets. We analyze in detail the several
populations observed, which include gammas, alphas, neutrons, thermal sensor
events and surface events, and try to combine all data sets to provide a
coherent picture of the nature and localisation of the background sources. In
light of this interpretation, we draw conclusions regarding the background
suppression scheme for the EDELWEISS-II phase
Measurement of the response of heat-and-ionization germanium detectors to nuclear recoils
The heat quenching factor Q' (the ratio of the heat signals produced by
nuclear and electron recoils of equal energy) of the heat-and-ionization
germanium bolometers used by the EDELWEISS collaboration has been measured. It
is explained how this factor affects the energy scale and the effective
quenching factor observed in calibrations with neutron sources. This effective
quenching effect is found to be equal to Q/Q', where Q is the quenching factor
of the ionization yield. To measure Q', a precise EDELWEISS measurement of Q/Q'
is combined with values of Q obtained from a review of all available
measurements of this quantity in tagged neutron beam experiments. The
systematic uncertainties associated with this method to evaluate Q' are
discussed in detail. For recoil energies between 20 and 100 keV, the resulting
heat quenching factor is Q' = 0.91+-0.03+-0.04, where the two errors are the
contributions from the Q and Q/Q' measurements, respectively. The present
compilation of Q values and evaluation of Q' represent one of the most precise
determinations of the absolute energy scale for any detector used in direct
searches for dark matter.Comment: 28 pages, 7 figures. Submitted to Phys. Rev.
One needs positive signatures for detection of Dark Matter
One believes there is huge amount of Dark Matter particles in our Galaxy
which manifest themselves only gravitationally. There is a big challenge to
prove their existence in a laboratory experiment. To this end it is not
sufficient to fight only for the best exclusion curve, one has to see an annual
recoil spectrum modulation --- the only available positive direct dark matter
detection signature. A necessity to measure the recoil spectra is stressed.Comment: 16 pages, 1 figure. arXiv admin note: substantial Appendix text
overlap with arXiv:0806.3917; missed acknowledge is added onl
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