596 research outputs found
WARP: a WIMP double phase Argon detector
The WARP programme for dark matter search with a double phase argon detector
is presented. In such a detector both excitation and ionization produced by an
impinging particle are evaluated by the contemporary measurement of primary
scintillation and secondary (proportional) light signal, this latter being
produced by extracting and accelerating ionization electrons in the gas phase.
The proposed technique, verified on a 2.3 liters prototype, could be used to
efficiently discriminate nuclear recoils, induced by WIMP's interactions, and
measure their energy spectrum. An overview of the 2.3 liters results and of the
proposed 100 liters detector is shown.Comment: Proceeding for IDM200
Demonstration and Comparison of Operation of Photomultiplier Tubes at Liquid Argon Temperature
Liquified noble gases are widely used as a target in direct Dark Matter
searches. Signals from scintillation in the liquid, following energy deposition
from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should
be recorded down to very low energies by photosensors suitably designed to
operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter
searches currently implement photo multiplier tubes for signal read-out. In the
last few years PMTs with photocathodes operating down to liquid Argon
temperatures (87 K) have been specially developed with increasing Quantum
Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod.
R11065 with peak QE up to about 35%, has been extensively tested within the R&D
program of the WArP Collaboration. During these testes the Hamamatsu PMTs
showed superb performance and allowed obtaining a light yield around 7
phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12%
range, sufficient for detection of events down to few keVee of energy
deposition. This shows that this new type of PMT is suited for experimental
applications, in particular for new direct Dark Matter searches with LAr-based
experiments
A new, very massive modular Liquid Argon Imaging Chamber to detect low energy off-axis neutrinos from the CNGS beam. (Project MODULAr)
The paper is considering an opportunity for the CERN/GranSasso (CNGS)
neutrino complex, concurrent time-wise with T2K and NOvA, to search for
theta_13 oscillations and CP violation. Compared with large water Cherenkov
(T2K) and fine grained scintillators (NOvA), the LAr-TPC offers a higher
detection efficiency and a lower backgrounds, since virtually all channels may
be unambiguously recognized. The present proposal, called MODULAr, describes a
20 kt fiducial volume LAr-TPC, following very closely the technology developed
for the ICARUS-T60o, and is focused on the following activities, for which we
seek an extended international collaboration:
(1) the neutrino beam from the CERN 400 GeV proton beam and an optimised horn
focussing, eventually with an increased intensity in the framework of the LHC
accelerator improvement program;
(2) A new experimental area LNGS-B, of at least 50000 m3 at 10 km off-axis
from the main Laboratory, eventually upgradable to larger sizes. A location is
under consideration at about 1.2 km equivalent water depth;
(3) A new LAr Imaging detector of at least 20 kt fiducial mass. Such an
increase in the volume over the current ICARUS T600 needs to be carefully
considered. It is concluded that a very large mass is best realised with a set
of many identical, independent units, each of 5 kt, "cloning" the technology of
the T600. Further phases may foresee extensions of MODULAr to meet future
physics goals.
The experiment might reasonably be operational in about 4/5 years, provided a
new hall is excavated in the vicinity of the Gran Sasso Laboratory and adequate
funding and participation are made available.Comment: Correspondig Author: C. Rubbia (E-mail: [email protected]), 33
pages, 11 figure
WARP liquid argon detector for dark matter survey
The WARP programme is a graded programme intended to search for cold Dark
Matter in the form of WIMP's. These particles may produce via weak interactions
nuclear recoils in the energy range 10-100 keV. A cryogenic noble liquid like
argon, already used in the realization of very large detector, permits the
simultaneous detection of both ionisation and scintillation induced by an
interaction, suggesting the possibility of discriminating between nuclear
recoils and electrons mediated events. A 2.3 litres two-phase argon detector
prototype has been used to perform several tests on the proposed technique.
Next step is the construction of a 100 litres sensitive volume device with
potential sensitivity a factor 100 better than presently existing experiments.Comment: Proceeding of the 6th UCLA Symposium on Sources and detection of Dark
Matter and dark Energy in the Univers
FLNA is implicated in pulmonary neuroendocrine tumors aggressiveness and progression
Pulmonary neuroendocrine tumors (PNTs) comprise different neoplasms, ranging from low grade carcinoids to the highly malignant small cell lung cancers. Several studies identified the cytoskeleton protein Filamin A (FLNA) as determinant in cancer progression and metastasis, but the role of FLNA in PNT aggressiveness and progression is still unknown. We evaluated FLNA expression in PNTs with different grade of differentiation, the role of FLNA in cell proliferation, colony formation, angiogenesis, cell adhesion and migration in PNT cell line (H727 cells) and primary cultures and the possible interaction between FLNA and Rap1-GTPase. FLNA is highly expressed in PNTs with high malignant grade. FLNA silencing reduces cyclin D1 levels (-51\uc2\ub15, p < 0.001) and cell proliferation in PNT cells (-37\uc2\ub14, p < 0.05), colony formation and VEGF expression (-39\uc2\ub19%, p < 0.01) in H727 cells. FLNA and Rap1 co-localize in cellular protrusions and FLNA silencing up-regulates Rap1 expression (+73\uc2\ub118%, p < 0.01). Rap1 silencing prevents cell adhesion increase (+43%\uc2\ub118%, p < 0.01) and cell migration decrease (-56\uc2\ub17%, p < 0.01) induced by FLNA silencing, without affecting cell proliferation reduction. In conclusion, FLNA is implicated in PNT progression, in part through Rap1, thus providing a potential diagnostic and therapeutic target
Discovery of underground argon with low level of radioactive 39Ar and possible applications to WIMP dark matter detectors
We report on the first measurement of 39Ar in argon from underground natural
gas reservoirs. The gas stored in the US National Helium Reserve was found to
contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be
<=4x10-17 (84% C.L.), less than 5% the value in atmospheric argon
(39Ar/Ar=8x10-16). The total quantity of argon currently stored in the National
Helium Reserve is estimated at 1000 tons. 39Ar represents one of the most
important backgrounds in argon detectors for WIMP dark matter searches. The
findings reported demonstrate the possibility of constructing large multi-ton
argon detectors with low radioactivity suitable for WIMP dark matter searches.Comment: 6 pages, 2 figures, 2 table
First results from a Dark Matter search with liquid Argon at 87 K in the Gran Sasso Underground Laboratory
A new method of searching for dark matter in the form of weakly interacting
massive particles (WIMP) has been developed with the direct detection of the
low energy nuclear recoils observed in a massive target (ultimately many tons)
of ultra pure Liquid Argon at 87 K. A high selectivity for Argon recoils is
achieved by the simultaneous observation of both the VUV scintillation
luminescence and of the electron signal surviving columnar recombination,
extracted through the liquid-gas boundary by an electric field. First physics
results from this method are reported, based on a small 2.3 litre test chamber
filled with natural Argon and an accumulated fiducial exposure of about 100 kg
x day, supporting the future validity of this method with isotopically purified
40Ar and for a much larger unit presently under construction with
correspondingly increased sensitivities.Comment: 26 pages, 8 figures, submitted to astroparticle physic
Towards a new Liquid Argon Imaging Chamber for the MODULAr project
The MODULAr project foresees the exploitation of a new liquid Argon imaging detector, of at least 20 kt fiducial mass, to be operated in a shallow depth location under the Gran Sasso Mountain. It will be devoted to study neutrino oscillations with an optimized off-axis CNGS neutrino beam. Cosmic neutrinos as well as proton decay will also be addressed. The MODULAr detector will vastly inherit from the technology developed for ICARUS-T600. However, such an increase in the volume over the current ICARUS-T600 needs to be carefully considered. It is concluded that a single, huge volume is an inoperable and uneconomical solution for many reasons. A very large mass is best realized with a modular set of many identical, independent units, each of about 5 kt, "cloning" the basic technology of the ICARUS-T600. Several of such modular units will be assembled to reach at least 20 kt as initial sensitive volume. The increase of the active volume of about one order of magnitude with respect to the ICARUS-T600 detector requires some specific R&D activity, which will be implemented in a similar to 360 ton prototype unit (SLICE) of reduced length
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