236 research outputs found
First measurement of the Head-Tail directional nuclear recoil signature at energies relevant to WIMP dark matter searches
We present first evidence for the so-called Head-Tail asymmetry signature of
neutron-induced nuclear recoil tracks at energies down to 1.5 keV/amu using the
1m^3 DRIFT-IIc dark matter detector. This regime is appropriate for recoils
induced by Weakly Interacting Massive Particle (WIMPs) but one where the
differential ionization is poorly understood. We show that the distribution of
recoil energies and directions induced here by Cf-252 neutrons matches well
that expected from massive WIMPs. The results open a powerful new means of
searching for a galactic signature from WIMPs.Comment: 4 pages, 6 figures, 1 tabl
Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches
Understanding the ability to measure and discriminate particle events at the
lowest possible energy is an essential requirement in developing new
experiments to search for weakly interacting massive particle (WIMP) dark
matter. In this paper we detail an assessment of the potential sensitivity
below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure,
negative ion time projection chamber (NITPC), based on event-by-event track
reconstruction and calorimetry in the multiwire proportional chamber (MWPC)
readout. By application of a digital smoothing polynomial it is shown that the
detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV
respectively, and 1.2 keV for electron induced events. The energy sensitivity
is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy
resolution is sufficient to identify the escape peak. The effect a lower energy
sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil
direction reconstruction for WIMP searches this sensitivity suggests new
prospects for applications also in KK axion searches
The DRIFT Dark Matter Experiments
The current status of the DRIFT (Directional Recoil Identification From
Tracks) experiment at Boulby Mine is presented, including the latest limits on
the WIMP spin-dependent cross-section from 1.5 kg days of running with a
mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with
ongoing work towards DRIFT III, which aims to be the world's first 10 m3-scale
directional Dark Matter detector.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
First Results from the DRIFT-IIa Dark Matter Detector
Data from the DRIFT-IIa directional dark matter experiment are presented,
collected during a near continuous 6 month running period. A detailed
calibration analysis comparing data from gamma-ray, x-ray and neutron sources
to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of
neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%. Software-based cuts,
designed to remove non-nuclear recoil events, are shown to reject 60Co
gamma-rays with a rejection factor of better than 8x10-6 for all energies above
threshold. An unexpected event population has been discovered and is shown here
to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the
central cathode. A limit on the flux of neutrons in the Boulby Underground
Laboratory is derived from analysis of unshielded and shielded data.Comment: 43 pages, 14 figures, submitted to Astroparticle Physic
Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator
Plastic scintillators are widely used in industry, medicine and scientific
research, including nuclear and particle physics. Although one of their most
common applications is in neutron detection, experimental data on their
response to low-energy nuclear recoils are scarce. Here, the relative
scintillation efficiency for neutron-induced nuclear recoils in a
polystyrene-based plastic scintillator (UPS-923A) is presented, exploring
recoil energies between 125 keV and 850 keV. Monte Carlo simulations,
incorporating light collection efficiency and energy resolution effects, are
used to generate neutron scattering spectra which are matched to observed
distributions of scintillation signals to parameterise the energy-dependent
quenching factor. At energies above 300 keV the dependence is reasonably
described using the semi-empirical formulation of Birks and a kB factor of
(0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured
quenching factor falls more steeply than predicted by the Birks formalism.Comment: 8 pages, 9 figure
The ZEPLIN-III dark matter detector: instrument design, manufacture and commissioning
We present details of the technical design and manufacture of the ZEPLIN-III
dark matter experiment. ZEPLIN-III is a two-phase xenon detector which measures
both the scintillation light and the ionisation charge generated in the liquid
by interacting particles and radiation. The instrument design is driven by both
the physics requirements and by the technology requirements surrounding the use
of liquid xenon. These include considerations of key performance parameters,
such as the efficiency of scintillation light collection, restrictions placed
on the use of materials to control the inherent radioactivity levels,
attainment of high vacuum levels and chemical contamination control. The
successful solution has involved a number of novel design and manufacturing
features which will be of specific use to future generations of direct dark
matter search experiments as they struggle with similar and progressively more
demanding requirements.Comment: 25 pages, 19 figures. Submitted to Astropart. Phys. Some figures down
sampled to reduce siz
The LAGUNA design study- towards giant liquid based underground detectors for neutrino physics and astrophysics and proton decay searches
The feasibility of a next generation neutrino observatory in Europe is being
considered within the LAGUNA design study. To accommodate giant neutrino
detectors and shield them from cosmic rays, a new very large underground
infrastructure is required. Seven potential candidate sites in different parts
of Europe and at several distances from CERN are being studied: Boulby (UK),
Canfranc (Spain), Fr\'ejus (France/Italy), Pyh\"asalmi (Finland),
Polkowice-Sieroszowice (Poland), Slanic (Romania) and Umbria (Italy). The
design study aims at the comprehensive and coordinated technical assessment of
each site, at a coherent cost estimation, and at a prioritization of the sites
within the summer 2010.Comment: 5 pages, contribution to the Workshop "European Strategy for Future
Neutrino Physics", CERN, Oct. 200
Background Assay and Rejection in DRIFT
The DRIFT-IId dark matter detector is a m3-scale low-pressure TPC with directional sensitivity to WIMP-induced nuclear recoils. Its primary backgrounds were due to alpha decays from contamination on the central cathode. Efforts to reduce these backgrounds led to replacing the 20 μm wire central cathode with one constructed from 0.9 μm aluminized mylar, which is almost totally transparent to alpha particles. Detailed modeling of the nature and origin of the remaining backgrounds led to an in-situ, ppt-sensitive assay of alpha decay backgrounds from the central cathode. This led to further improvements in the thin-film cathode resulting in over 2 orders of magnitude reduction in backgrounds compared to the wire cathode. Finally, the addition of O2 to CS2 gas was found to produce multiple species of electronegative charge carriers, providing a method to determine the absolute position of nuclear recoils and reject all known remaining backgrounds while retaining a high efficiency for nuclear recoil detection
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