Expected Performance of CryoArray

WIMP-nucleon cross sections below 10^(-9) pb may be probed by ton-scale experiments with low thresholds and background rates ~20 events per year. An array of cryogenic detectors ("CryoArray") could perform well enough to reach this goal. Sufficient discrimination and background suppression of photons has already been demonstrated. Reduction of neutron backgrounds may be achieved by siting the experiment deep enough. Removal of the surface-electron backgrounds alone has not yet been demonstrated, but the reductions required even for this troublesome background are quite modest and appear achieveable.Comment: 4 pages, 2 figures. Talk at DM2002 Conference, Marina del Rey, CA, Feb 20-22, 200

Towards One Tonne Direct WIMP Detectors: Have we got what it takes?

Experimentally have we got what it takes to pursue the direct observation of WIMP interactions down to sensitivities of a few events /100 kg/year? For a Ge target with a low energy threshold (<20 keVr) this corresponds to a WIMP-nucleon sigma~10^-46 cm^2. A number of recent theoretical papers, making calculations in SUSY-based frameworks, show many (>5) orders of magnitude spread in the possible interaction rates for models consistent with existing Cosmology and Accelerator bounds. Some theorists, but certainly not all, are able to generate models, that lead to interaction rates at the few /kg/day that would be implied by the current DAMA annual modulation signal. All theorists demonstrate models that generate much lower interaction rates. This paper takes an unashamed experimentalist`s view of the issues that arise when looking forward to constructing 1 tonne WIMP detectors.Comment: 12 pages (TeX), 6 figures (eps); IDM2000 3rd International Workshop on the Identification of Dark Matter, York, UK, to be published in proceedings Eds. N. J. C. Spooner and V. Kudryavtsev, World Scientific, Singapore, 2001. Slides available at http://www.hep.ucl.ac.uk/~gaitske

Race, gender and imperialism: A century of black girls' education in South Africa

African Studies Seminar series. Paper presented August, 198

Women, religion and medicine in Johannesburg between the wars

African Studies Seminar series. Paper presented 19 August, 1982In explaining the growth of independent churches among the Shona since the 1930s, Daneel lays great stress on the attraction for ordinary members of the curative powers offered by the church. Many joined because they personally or close relatives were cured in faith healing sessions. Unlike churches of outside origin, the African churches took evil forces seriously and combated them in a way appealing to the patient's mind. Diagnostic sessions grappling with the spiritual causes of misfortune seemed to be the key to success. Daneel, like other modern commentators, takes a much more positive view of prophetic therapeutic treatment, seeing it as essentially Christian in character.(1

'Christian compounds for girls': church hostels for African women in Johannesburg, 1907-1970.

African Studies Seminar series. Paper presented August, 1977Compounds in the mining industry gave Rand and Kimberley capitalists a vital means of industrial and police control of their labour force, as well as enabling them “to provide amenities such as recreation and health supervision” (1), no less important for the smooth running of the mines. Local authorities adapted this idea, in open compounds for casual labourers and, as Davenport has noted, 'it was a short step from the municipal compound to the “native hostel”, which became a common feature of municipal locations in the larger centres under the stimulus of the Urban Areas Act of 1923.'(2) This paper examines three hostels for African women which were established in Johannesburg by missionaries of the Anglican and Methodist Churches, and the American Board Mission

A New Model-Independent Method for Extracting Spin-Dependent Cross Section Limits from Dark Matter Searches

A new method is proposed for extracting limits on spin-dependent WIMP-nucleon interaction cross sections from direct detection dark matter experiments. The new method has the advantage that the limits on individual WIMP-proton and WIMP-neutron cross sections for a given WIMP mass can be combined in a simple way to give a model-independent limit on the properties of WIMPs scattering from both protons and neutrons in the target nucleus. Extension of the technique to the case of a target material consisting of several different species of nuclei is discussed.Comment: 15 pages, 6 Encapsulated Postscript figure

Swift observation of Segue 1: constraints on sterile neutrino parameters in the darkest galaxy

Some extensions of standard particle physics postulate that dark matter may be partially composed of weakly interacting sterile neutrino particles that have so far eluded detection. We use a short (~5 ks) archival X-ray observation of Segue 1 obtained with the X-ray Telescope (XRT) onboard the Swift satellite to exclude the presence of sterile neutrinos in the 1.6 - 14 keV mass range down to a flux limit of 6 x 10^{-12} erg cm-2 s-1 within 67 pc of its centre. With an estimated mass-to-light ratio of ~3400 Msun/Lsun, Segue 1 is the darkest ultrafaint dwarf galaxy currently measured. Spectral analysis of the Swift XRT data fails to find any non-instrumental spectral feature possibly connected with the radiative decay of a dark matter particle. Accordingly, we establish upper bounds on the sterile neutrino parameter space based on the non-detection of emission lines in the spectrum. The present work provides the most sensitive X-ray search for sterile neutrinos in a region with the highest dark matter density yet measured.Comment: 5 pages, 3 figures. Accepted in MNRAS Letter

Characterization of a Li-6 loaded liquid organic scintillator for fast neutron spectrometry and thermal neutron detection

The characterization of a liquid scintillator incorporating an aqueous solution of enriched lithium chloride to produce a scintillator with 0.40% Li-6 is presented, including the performance of the scintillator in terms of its optical properties and neutron response. The scintillator was incorporated into a fast neutron spectrometer, and the light output spectra from 2.5 MeV, 14.1 MeV, and Cf-252 neutrons were measured using capture-gated coincidence techniques. The spectrometer was operated without coincidence to perform thermal neutron measurements. Possible improvements in spectrometer performance are discussed.Comment: Submitted to Applied Radiation and Isotopes. 11 pages, 7 figures, 3 tables. Revision addresses reviewers' comment