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Register a new userCharacterization of the Response of Superheated Droplet (Bubble) Detectors
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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.
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The combined measurement of dark matter interactions with different superheated liquids has recently been suggested as a cross-correlation technique in identifying WIMP candidates. We describe the fabrication of high concentration superheated droplet detectors based on the light nuclei liquids C3F8, C4F8, C4F10 and CCl2F2, and investigation of their irradiation response with respect to C2ClF5. The results are discussed in terms of the basic physics of superheated liquid response to particle interactions, as well as the necessary detector qualifications for application in dark matter search investigations. The possibility of heavier nuclei SDDs is explored using the light nuclei results as a basis, with CF3I provided as an example.
The simulation of the neutron background for Phase II of the SIMPLE direct dark matter search experiment is fully reported with various improvements relative to previous estimates. The model employs the Monte Carlo MCNP neutron transport code, using as input a realistic geometry description, measured radioassays and material compositions, and tabulated (alpha,n) yields and spectra. Developments include the accounting of recoil energy distributions, consideration of additional reactions and materials and examination of the relevant (alpha,n) data. A thorough analysis of the simulation results is performed that addresses an increased number of non-statistical uncertainties. The referred omissions are seen to provide a net increase of 13$%$ in the previously-reported background estimates whereas the non-statistical uncertainty rises to 25$%$. The final estimated recoil event rate is 0.372 $pm$ 0.002 (stat.) $pm$ 0.097 (non-stat.) evt/kgd resulting in insignificant changes over the results of the experiment.
We discuss a quantum description of bubble growth in a superheated liquid Helium by addressing the problem of operator ordering ambiguities that arise due to the presence of position dependent mass (PDM) in this system. Using a supersymmetric quantum mechanics formalism along with the Weyl quantization rule, we are able to identify specific operator orderings for this problem. This is a general method which should be applicable to other PDM systems.
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 about room temperature and ambient pressure. The phase transition is induced by nuclear recoils when an atomic nucleus in the droplets interacts with incoming subatomic particles. This includes CDM particles candidate as the neutralino (a yet-to-discover particle predicted in extensions of the Standard Model of particle physics). Simulations performed to understand the detector response to neutrons and alpha particles are presented along with corresponding data obtained at the Montreal Laboratory.
A study on cosmic muons has been performed for the two identical near and far neutrino detectors of the Double Chooz experiment, placed at $sim$120 and $sim$300 m.w.e. underground respectively, including the corresponding simulations using the MUSIC simulation package. This characterization has allowed to measure the muon flux reaching both detectors to be (3.64 $pm$ 0.04) $times$ 10$^{-4}$ cm$^{-2}$s$^{-1}$ for the near detector and (7.00 $pm$ 0.05) $times$ 10$^{-5}$ cm$^{-2}$s$^{-1}$ for the far one. The seasonal modulation of the signal has also been studied observing a positive correlation with the atmospheric temperature, leading to an effective temperature coefficient of $alpha_{T}$ = 0.212 $pm$ 0.024 and 0.355 $pm$ 0.019 for the near and far detectors respectively. These measurements, in good agreement with expectations based on theoretical models, represent one of the first measurements of this coefficient in shallow depth installations.
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