Department of Physics and Astronomy

Permanent link for this collectionhttps://hdl.handle.net/2022/22354

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Browsing Department of Physics and Astronomy by Subject "Dark matter (Astronomy)"

Now showing 1 - 7 of 7
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    Constraints on low-mass WIMP interactions on 19F from PICASSO
    (Elsevier, 2012) Archambault, Simon; Behnke, Ed; Grace, Emily A.; Levine, Ilan
    Recent results from the PICASSO dark matter search experiment at SNOLAB are reported. These results were obtained using a subset of 10 detectors with a total target mass of 0.72 kg of 19F and an exposure of 114 kgd. The low backgrounds in PICASSO allow recoil energy thresholds as low as 1.7 keV to be obtained which results in an increased sensitivity to interactions from Weakly Interacting Massive Particles (WIMPs) with masses below 10 GeV/c2. No dark matter signal was found. Best exclusion limits in the spin dependent sector were obtained for WIMP masses of 20 GeV/c2 with a cross section on protons of σ SD p = 0.032 pb (90% C.L.). In the spin independent sector close to the low mass region of 7 GeV/c2 favoured by CoGeNT and DAMA/LIBRA, cross sections larger than σ S I p = 1.41 × 10−4 pb (90% C.L.) are excluded. Keywords: Dark matter, WIMPs, Superheated droplets, SNOLAB
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    Dark Matter Spin-Dependent Limits for WIMP Interactions on 19F by PICASSO
    (Elsevier, 2009-11) Archambault, S.; Aubin, F.; Auger, M.; Behnke, Ed; Beltran, B.; Clark, K.; Dai, X.; Davour, A.; Farine, J.; Faust, R.; Genest, M.-H.; Giroux, G.; Gornea, R.; Krauss, C.; Kumaratunga, S.; Lawson, I.; Leroy, C.; Lessard, L.; Levy, C.; Levine, Ilan; MacDonald, R.; Martin, J.-P.; Nadeau, P.; Noble, A.; Piro, M.-C.; Pospisil, S.; Shephed, T.; Starinski, N.; Stekl, I.; Storey, C.; Wichoski, U.; Zacek, V.
    The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP interactions on 19F using the superheated droplet technique. A new generation of detectors and new features which enable background discrimination via the rejection of non-particle induced events are described. First results are presented for a subset of two detectors with target masses of 19F of 65 g and 69 g respectively and a total exposure of 13.75 ± 0.48 kgd. No dark matter signal was found and for WIMP masses around 24 GeV/c2 new limits have been obtained on the spin-dependent cross section on 19F of oF = 13.9 pb (90% C.L.) which can be converted into cross section limits on protons and neutrons of op = 0.16 pb and on = 2.60 pb respectively (90% C.L). The obtained limits on pro-tons restrict recent interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent interactions. Keywords: dark matter, WIMPS, superheated droplets, NOLABPACS:95.35.+d, 29.40.-n, 34.50.BW
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    Discrimination of nuclear recoils from alpha particles with superheated liquids
    (New Journal of Physics, 2008) Aubin, F.; Auger, M.; Genest, M.-H.; Giroux, G.; Gornea, R.; Faust, R.; Leroy, C.; Lessard, L.; Martin, J.-P.; Morlat, T.; Piro, M.-C.; Starinski, N.; Zacek, V.; Beltran, B.; Krauss, C. B.; Behnke, Ed; Levine, Ilan; Shepherd, T.; Nadeau, P.; Wichoski, U.; Pospisil, S.; Stekl, I.; Sodomka, J.; Clark, K.; Dai, X.; Davour, A.; Levy, C.; Noble, A. J.; Storey, C.
    The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron induced recoils.
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    First Dark Matter Search Results from a 4-kg CF3I Bubble Chamber Operated in a Deep Underground Site
    (American Physical Society, 2012-09) Behnke, Ed; Behnke, Joshua; Conner, A.; Grace, Emily A.; Levine, Ilan; Moan, T.; Nania, T.
    New data are reported from the operation of a 4.0 kg CF3I bubble chamber in the 6800 foot deep SNOLAB underground laboratory. The effectiveness of ultrasound analysis in discriminating alpha decay background events from single nuclear recoils has been confirmed, with a lower bound of >99.3% rejection of alpha decay events. Twenty single nuclear recoil event candidates and three multiple bubble events were observed during a total exposure of 553 kg-days distributed over three different bubble nucleation thresholds. The effective exposure for single bubble recoil-like events was 437.4 kg-days. A neutron background internal to the apparatus, of known origin, is estimated to account for five single nuclear recoil events and is consistent with the observed rate of multiple bubble events. The remaining excess of single bubble events exhibits characteristics indicating the presence of an additional background. These data provide new direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses >20 GeV/c2 and demonstrate significant sensitivity for spin-independent interactions.
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    Improved Limits on Spin-Dependent WIMP-Proton Interactions from a Two Liter CF3I Bubble Chamber
    (American Physical Society, 2011-03) Behnke, Ed; Behnke, J.; Hinnefeld, Jerry; Levine, Ilan; Shepherd, T.
    Data from the operation of a bubble chamber filled with 3.5 kg of CF3I in a shallow underground site are reported. An analysis of ultrasound signals accompanying bubble nucleations confirms that alpha decays generate a significantly louder acoustic emission than single nuclear recoils, leading to an efficient background discrimination. Three dark matter candidate events were observed during an effective exposure of 28.1 kg-day, consistent with a neutron background. This observation provides strong direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses > 20 GeV/c2.
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    Improved Spin Dependent Limits from the PICASSO Dark Matter Search Experiment
    (Elsevier, 2005-09) Barnabe-Heider, Marik; Behnke, Joshua; Feighery, William.; Levine, Ilan; Muthusi, Cynthia
    The PICASSO experiment reports an improved limit for the existence of cold dark matter WIMPs interacting via spin-dependent interactions with nuclei. The experiment is installed in the Sudbury Neutrino Observatory at a depth of 2070 m. With superheated C4F10 droplets as the active material, and an exposure of 1.98±0.19 kgd, no evidence for a WIMP signal was found. For a WIMP mass of 29 GeV/c2, limits on the spin-dependent cross section on protons of σp = 1.31 pb and on neutrons of σn = 21.5 pb have been obtained at 90% C.L. In both cases, some new parameter space in the region of WIMP masses below 20 GeV/c2 has now been ruled out. The results of these measurements are also presented in terms of limits on the effective WIMP-proton and neutron coupling strengths ap and an.
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    New Insights into Particle Detection with Superheated Liquids
    (IOP Publishing, 2010-11) Archambault, Simon; Behnke, Ed; Behnke, Joshua; Hinnefeld, Jerry; Levine, Ilan; Vander Werf, Nathan P.
    We report new results obtained in calibrations of superheated liquid droplet detectors used in dark matter searches with different radiation sources (n,α,γ). In particular, detectors were spiked with alpha-emitters located inside and outside the droplets. It is shown that the responses are different, depending on whether alpha particles or recoil nuclei create the signals. The energy thresholds for α-emitters are compared with test beam measurements using mono-energetic neutrons, as well as with theoretical predictions. Finally a model is presented which describes how the observed intensities of particle induced acoustic signals can be related to the dynamics of bubble growth in superheated liquids. An improved understanding of the bubble dynamics is an important first step in obtaining better discrimination between particle types interacting in detectors of this kind.