Implementation of a local principal curves algorithm for neutrino interaction reconstruction in a liquid argon volume

A local principal curve algorithm has been implemented in three dimensions for automated track and shower reconstruction of neutrino interactions in a liquid argon time projection chamber. We present details of the algorithm and characterise its performance on simulated data sets.Comment: 14 pages, 17 figures; typing correction to Eq 5, the definition of the local covariance matri

Moving away from flat solar panels to PVtrees : exploring ideas and people's perceptions

Photovoltaic Trees (PVTrees) are artificial solar structures that look like sculptural trees and exist from small scale (size of a bonsai tree) to large scale (about the size of a wind turbine). The aesthetics of solar trees differ and they have been designed to provide different means of power to different urban and built environments. These range from powering mobile phones, electric cars, buildings and street lights covering small and large scale areas (one or a forest of PVTrees). This study brought together a research team of physicists and designers and to conduct focus groups with design based methods and prototyping (clustering of ideas, sketching and modelling) along with a computational 3D PVTree design tool. The focus groups consisted of capturing a) people's perception on PVTrees, idea generations and development of the 3D model and b) further discussion and evaluation of insights. A public exhibition followed to capture public perception on design concepts using 3D models, and a voting exercise. Overall it was found that PVTrees were received positively by the public with desires for them to be multifunctional by providing power yet also having a secondary function e.g. a shelter or seat. The paper details this, considerations for concept development, and the future direction of research in the area

Electron-hadron shower discrimination in a liquid argon time projection chamber

By exploiting structural differences between electromagnetic and hadronic showers in a multivariate analysis we present an efficient Electron-Hadron discrimination algorithm for liquid argon time projection chambers, validated using Geant4 simulated data

The CRESST Dark Matter Search

We present first competitive results on WIMP dark matter using the phonon-light-detection technique. A particularly strong limit for WIMPs with coherent scattering results from selecting a region of the phonon-light plane corresponding to tungsten recoils. The observed count rate in the neutron band is compatible with the rate expected from neutron background. CRESST is presently being upgraded with a 66 channel SQUID readout system, a neutron shield and a muon veto system. This results in a significant improvement in sensitivity.Comment: 6 pages, 3 figures, to be published in the proceedings of the 5th International Workshop on the Identification and Detection of Dark Matter IDM 2004, Edinburgh, Sept. 2004, World Scientifi

The CRESST Experiment: Recent Results and Prospects

The CRESST experiment seeks hypothetical WIMP particles that could account for the bulk of dark matter in the Universe. The detectors are cryogenic calorimeters in which WIMPs would scatter elastically on nuclei, releasing phonons. The first phase of the experiment has successfully deployed several 262 g sapphire devices in the Gran Sasso underground laboratories. A main source of background has been identified as microscopic mechanical fracturing of the crystals, and has been eliminated, improving the background rate by up to three orders of magnitude at low energies, leaving a rate close to one count per day per kg and per keV above 10 keV recoil energy. This background now appears to be dominated by radioactivity, and future CRESST scintillating calorimeters which simultaneously measure light and phonons will allow rejection of a great part of it.Comment: To appear in the proceedings of the CAPP2000 Conference, Verbier, Switzerland, July, 2000 (eds J. Garcia-Bellido, R. Durrer, and M. Shaposhnikov

Detection of the Natural Alpha Decay of Tungsten

The natural alpha decay of 180W has been unambiguously detected for the first time. The alpha peak is found in a (gamma,beta and neutron)-free background spectrum. This has been achieved by the simultaneous measurement of phonon and light signals with the CRESST cryogenic detectors. A half-life of T1/2 = (1.8 +- 0.2) x 10^18 y and an energy release of Q = (2516.4 +- 1.1 (stat.) +- 1.2 (sys.)) keV have been measured. New limits are also set on the half-lives of the other naturally occurring tungsten isotopes.Comment: Submitted to Physical Review C Revised versio

New limits on dark--matter WIMPs from the Heidelberg--Moscow experiment

New results after 0.69 kg yr of measurement with an enriched 76Ge detector of the Heidelberg--Moscow experiment with an active mass of 2.758 kg are presented. An energy threshold of 9 keV and a background level of 0.042 counts/(kg d keV) in the energy region between 15 keV and 40 keV was reached.The derived limits on the WIMP--nucleon cross section are the most stringent limits on spin--independent interactions obtained to date by using essentially raw data without background subtraction.Comment: 8 pages (latex) including 5 postscript figures and 2 tables. To appear in Phys. Rev. D, 15. December 199