517 research outputs found
Extracting constraints from direct detection searches of supersymmetric dark matter in the light of null results from the LHC in the squark sector
The comparison of the results of direct detection of Dark Matter, obtained
with various target nuclei, requires model-dependent, or even arbitrary,
assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the
spin-independent (SI) interaction has to be neglected. In the light of the null
results from supersymmetry searches at the LHC, the squark sector is pushed to
high masses. We show that for a squark sector at the TeV scale, the framework
used to extract contraints from direct detection searches can be redefined as
the number of free parameters is reduced. Moreover, the correlation observed
between SI and SD proton cross sections constitutes a key issue for the
development of the next generation of Dark Matter detectors.Comment: Figure 3 has been updated. Conclusions unchange
An analysis method for time ordered data processing of Dark Matter experiments
The analysis of the time ordered data of Dark Matter experiments is becoming
more and more challenging with the increase of sensitivity in the ongoing and
forthcoming projects. Combined with the well-known level of background events,
this leads to a rather high level of pile-up in the data. Ionization,
scintillation as well as bolometric signals present common features in their
acquisition timeline: low frequency baselines, random gaussian noise, parasitic
noise and signal characterized by well-defined peaks. In particular, in the
case of long-lasting signals such as bolometric ones, the pile-up of events may
lead to an inaccurate reconstruction of the physical signal (misidentification
as well as fake events). We present a general method to detect and extract
signals in noisy data with a high pile-up rate and qe show that events from few
keV to hundreds of keV can be reconstructed in time ordered data presenting a
high pile-up rate. This method is based on an iterative detection and fitting
procedure combined with prior wavelet-based denoising of the data and baseline
subtraction. {We have tested this method on simulated data of the MACHe3
prototype experiment and shown that the iterative fitting procedure allows us
to recover the lowest energy events, of the order of a few keV, in the presence
of background signals from a few to hundreds of keV. Finally we applied this
method to the recent MACHe3 data to successfully measure the spectrum of
conversion electrons from Co57 source and also the spectrum of the background
cosmic muons
A superfluid He3 detector for direct dark matter search
MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter Search. The idea is to use superfluid He3 as a sensitive
medium. The existing device, the superfluid He3 cell, will be briefly
introduced. Then a description of the MACHe3 project will be presented, in
particular the background rejection and the neutralino event rate that may be
achieved with such a device.Comment: 6 pages, 3 figures, Proceedings of the 3rd International Workshop on
the Identification of Dark Matter (York, UK, 09/18/2000-09/22/2000
A project of a new detector for direct Dark Matter search: MACHe3
MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter (DM) search. A cell of superfluid He3 has been developed and
the idea of using a large number of such cells in a high granularity detector
is proposed.This contribution presents, after a brief description of the
superfluid He3 cell, the simulation of the response of different matrix
configurations allowing to define an optimum design as a function of the number
of cells and the volume of each cell. The exclusion plot and the predicted
interaction cross-section for the neutralino as a photino are presented.Comment: 8 pages, 7 figures, Proceedings of Dark Matter 2000 (Marina Del Rey,
Los Angeles, USA, 02/23/2000-02/25/2000
Bolometric calibration of a superfluid He detector for Dark Matter search: direct measurement of the scintillated energy fraction for neutron, electron and muon events
We report on the calibration of a superfluid He bolometer developed for
the search of non-baryonic Dark Matter. Precise thermometry is achieved by the
direct measurement of thermal excitations using Vibrating Wire Resonators
(VWRs). The heating pulses for calibration were produced by the direct quantum
process of quasiparticle generation by other VWRs present. The bolometric
calibration factor is analyzed as a function of temperature and excitation
level of the sensing VWR. The calibration is compared to bolometric
measurements of the nuclear neutron capture reaction and heat depositions by
cosmic muons and low energy electrons. The comparison allows a quantitative
estimation of the ultra-violet scintillation rate of irradiated helium,
demonstrating the possibility of efficient electron recoil event rejection.Comment: 17 pages, submitted to Nuc. Instr. Meth.
Design optimization of MACHe3, a project of superfuid Detector for direct Dark Matter search
MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector fordirect Dark Matter (DM) search. A cell of superfluid He3 has been developed andthe idea of using a large number of such cells in a high granularity detectoris proposed. This paper presents, after a brief description of the superfluidHe3 cell, the simulation of the response of different matrix configurationsallowing to define an optimum design as a function of the number of cells andthe volume of each cell. The background rejection, for several configurations,is presented both for neutrons and gamma-rays of various kinetic energies
MACHe3: A new generation detector for non-baryonic dark matter direct detection
MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter (DM) search, using superfluid as a sensitive medium. An
experiment on a prototype cell has been performed and the first results
reported here are encouraging to develop of a multicell prototype. In order to
investigate the discovery potential of MACHe3, and its complementarity with
other DM detectors, a phenomenological study done with the DarkSUSY code is
shown.Comment: 6 pages, 3 figures, Proceedings of the 4th International Workshop on
the Identification of Dark Matter (York, UK, 09/02/2002-09/06/2002
Health promotion: From malaria control to elimination
Here we reflect on the achievement of some of the diverse activities that have brought malaria under control, highlight key challenges and propose specific health promotion interventions required to move South Africa’s malaria programme from control to elimination
Sub-wavelength surface IR imaging of soft-condensed matter
Outlined here is a technique for sub-wavelength infrared surface imaging
performed using a phase matched optical parametric oscillator laser and an
atomic force microscope as the detection mechanism. The technique uses a novel
surface excitation illumination approach to perform simultaneously chemical
mapping and AFM topography imaging with an image resolution of 200 nm. This
method was demonstrated by imaging polystyrene micro-structures
Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY
The ARES linac at DESY aims to generate and characterize ultrashort electron
bunches (fs to sub-fs duration) with high momentum and arrival time stability
for the purpose of applications related to accelerator R&D, e.g. development of
advanced and compact diagnostics and accelerating structures, test of new
accelerator components, medical applications studies, machine learning, etc.
During its commissioning phase, the bunch duration characterization of the
electron bunches generated at ARES has been performed with an RF-phasing
technique relying on momentum spectra measurements, using only common
accelerator elements (RF accelerating structures and magnetic spectrometers).
The sensitivity of the method allowed highlighting different response times for
Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of
machine parameters shows excellent agreement overall with the simulation
predictions, thus demonstrating a very good understanding of the ARES operation
on the bunch duration aspect. The importance of a precise in-situ experimental
determination of the phase velocity of the first travelling wave accelerating
structure after the electron source, for which we propose a simple new
beam-based method precise down to sub-permille variation respective to the
speed of light in vacuum, is emphasized for this purpose. A minimum bunch
duration of 20 fs rms, resolution-limited by the space charge forces, is
reported. This is, to the best of our knowledge, around 4 times shorter than
what has been previously experimentally demonstrated based on RF-phasing
techniques with a single RF structure. The present study constitutes a strong
basis for future time characterization down to the sub-fs level at ARES, using
dedicated X-band transverse deflecting structures.Comment: 17 pages, 11 figures. To be submitted to Physical Review Accelerators
and Beam
- …