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Recherche de matière sombre non-baryonique au moyen d'un bolomètre à ionisation dans le cadre de l'expérience EDELWEISS

Abstract : The EDELWEISS experiment is an underground direct-detection search for hypothetical supersymmetric WIMPs that might solve the problem of dark matter. We have employed a cryogenic 70 g germanium ionisation bolometer, in which a WIMP would scatter elastically off a nucleus, creating both a heat and an ionisation signal. To offset the various electronic noises present in our necessarily small signals, we have applied an optimal filtering technique in the frequency domain. This allows us to reach resolutions of 1.2 keV FWHM at 122 keV on both channels. It also provides good separation right down to low energies between the expected signal of nuclear recoils, and the photonic background of electron recoils which ionise more for a given energy. Calibration data show that we are able to reject 99.7% of this background, while keeping 95% of the signal. However, our 1.17 kg.days of data searching for WIMPs show a third population encroaching on the expected signal. This is probably due to low energy photons or electrons interacting in the outer layers of the crystal, where charges are incompletely collected. Nevertheless, by trading off half of the conserved signal, we still manage to reject 98.5% of the background. Thus the raw rate of 40 evts/d/kg/keV yields a conservative 90% upper limit on the signal of 0.6 evts/d/kg/keV. This represents nearly a three orders of magnitude improvement for EDELWEISS, and puts the predicted supersymmetric phase space within two orders of magnitude.
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Contributor : Philippe Di Stefano <>
Submitted on : Monday, May 16, 2005 - 11:25:53 AM
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  • HAL Id : tel-00009267, version 1



Philippe Di Stefano. Recherche de matière sombre non-baryonique au moyen d'un bolomètre à ionisation dans le cadre de l'expérience EDELWEISS. Cosmologie et astrophysique extra-galactique [astro-ph.CO]. Université Paris Sud - Paris XI, 1998. Français. ⟨tel-00009267⟩



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