Charge amplification concepts for direction-sensitive dark matter detectors

Direction measurement of weakly interacting massive particles in time-projection chambers can provide definite evidence of their existence and help to determine their properties. This article demonstrates several concepts for charge amplification in time-projection chambers that can be used in direction-sensitive dark matter search experiments. We demonstrate reconstruction of the 'head-tail' effect for nuclear recoils above 100keV, and discuss the detector performance in the context of dark matter detection and scaling to large detector volumes.Comment: 15 pages, 9 figure

Data acquisition electronics and reconstruction software for directional detection of Dark Matter with MIMAC

Directional detection of galactic Dark Matter requires 3D reconstruction of low energy nuclear recoils tracks. A dedicated acquisition electronics with auto triggering feature and a real time track reconstruction software have been developed within the framework of the MIMAC project of detector. This auto-triggered acquisition electronic uses embedded processing to reduce data transfer to its useful part only, i.e. decoded coordinates of hit tracks and corresponding energy measurements. An acquisition software with on-line monitoring and 3D track reconstruction is also presented.Comment: 17 pages, 12 figure

A Measurement of Photon Production in Electron Avalanches in CF4

This paper presents a measurement of the ratio of photon to electron production and the scintillation spectrum in a popular gas for time pro jection chambers, carbon tetrafluoride (CF4), over the range of 200 to 800 nm; the ratio is measured to be 0.34+/-0.04. This result is of particular importance for a new generation of dark matter time projection chambers with directional sensitivity which use CF4 as a fill gas.Comment: 19 pages, including appendix. 8 figure

Background Rejection in the DMTPC Dark Matter Search Using Charge Signals

The Dark Matter Time Projection Chamber (DMTPC) collaboration is developing low-pressure gas TPC detectors for measuring WIMP-nucleon interactions. Optical readout with CCD cameras allows for the detection for the daily modulation in the direction of the dark matter wind, while several charge readout channels allow for the measurement of additional recoil properties. In this article, we show that the addition of the charge readout analysis to the CCD allows us too obtain a statistics-limited 90% C.L. upper limit on the $e^-$ rejection factor of $5.6\times10^{-6}$ for recoils with energies between 40 and 200 keV$_{\mathrm{ee}}$. In addition, requiring coincidence between charge signals and light in the CCD reduces CCD-specific backgrounds by more than two orders of magnitude.Comment: 8 pages, 6 figures. For proceedings of DPF 2011 conferenc

Directional detection as a strategy to discover Galactic Dark Matter

Directional detection of Galactic Dark Matter is a promising search strategy for discriminating genuine WIMP events from background ones. Technical progress on gaseous detectors and read-outs has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its galactic origin. This is a blind analysis intended to be used on any directional data. Constraints are deduced in the ($\sigma_n, m_\chi$) plane and systematic studies are presented in order to show that, using this analysis tool, unambiguous dark matter detection can be achieved on a large range of exposures and background levels.Comment: 20 pages, 5 figures Final version to appear in Phys. Lett.

Ultra-fine dark matter structure in the Solar neighbourhood

The direct detection of dark matter on Earth depends crucially on its density and its velocity distribution on a milliparsec scale. Conventional N-body simulations are unable to access this scale, making the development of other approaches necessary. In this paper, we apply the method developed in Fantin et al. 2008 to a cosmologically-based merger tree, transforming it into a useful instrument to reproduce and analyse the merger history of a Milky Way-like system. The aim of the model is to investigate the implications of any ultra-fine structure for the current and next generation of directional dark matter detectors. We find that the velocity distribution of a Milky Way-like Galaxy is almost smooth, due to the overlap of many streams of particles generated by multiple mergers. Only the merger of a 10^10 Msun analyse can generate significant features in the ultra-local velocity distribution, detectable at the resolution attainable by current experiments.Comment: 9 pages, 6 figures, accepted for publication in MNRA