arXiv subjects

J. Behnke

Publications and source records attributed to J. Behnke.

5 recordsLinked to original sources

arXiv2012

First dark matter search results from a 4-kg CF$_3$I bubble chamber operated in a deep underground site

New data are reported from the operation of a 4.0 kg CF$_{3}$I 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. This observation provides world best direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses $>$20 GeV/c$^{2}$ and demonstrates significant sensitivity for spin-independent interactions.

astro-ph.CO↗

arXiv2011

Improved Limits on Spin-Dependent WIMP-Proton Interactions from a Two Liter CF$_3$I Bubble Chamber

Data from the operation of a bubble chamber filled with 3.5 kg of CF$_{3}$I 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 the strongest direct detection constraint to date on WIMP-proton spin-dependent scattering for WIMP masses $>20$ GeV/c$^{2}$.

astro-ph.CO↗

arXiv2010

New Insights into Particle Detection with Superheated Liquids

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.

physics.ins-det↗

arXiv2003

Status of the PICASSO Project

The Picasso project is a dark matter search experiment based on the superheated droplet technique. Preliminary runs performed at the Picasso Lab in Montreal have showed the suitability of this detection technique to the search for weakly interacting cold dark matter particles. In July 2002, a new phase of the project started. A batch of six 1-liter detectors with an active mass of approximately 40g was installed in a gallery of the SNO observatory in Sudbury, Ontario, Canada at a depth of 6,800 feet (2,070m). We give a status report on the new experimental setup, data analysis, and preliminary limits on spin-dependent neutralino interaction cross section.

hep-ex↗

arXiv2003

Characterization of the Response of Superheated Droplet (Bubble) Detectors

The PICASSO project is a cold dark matter (CDM) search experiment relying on the superheated droplet technique. The detectors use superheated freon liquid droplets (active material) dispersed and trapped in a polymerized gel. This detection technique is based on the phase transition of superheated droplets at room or moderate temperatures. The phase transitions are induced by nuclear recoils when undergoing interactions with particles, including CDM candidates such as the neutralinos predicted by supersymmetric models. The suitability of the technique for this purpose has been demonstrated by R&D studies performed over several years on detectors of various composition and volume. Simulations performed to understand the detector response to neutrons and alpha particles are presented along with corresponding data obtained at the Montreal Laboratory.

hep-ex↗