12 research outputs found
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In-situ low-energy background measurement in D2O+salt phase of the Sudbury Neutrino Observatory, using the isotropy of ß-? Cerenkov light
In the second phase of the Sudbury Neutrino Observatory (SNO), salt was added to the D2O, increasing the sensitivity to measurement of the 8B solar neutrino flux through the neutral current reaction, in which the deuteron is split into its proton and its neutron. This reaction is detected by looking for the Cerenkov light which is produced when the neutron is captured on the salt or on the D2O. In this article, I will describe the in-situ method used for the determination of the neutron background from radioactivity within the D2O, as presented in [SNO Collaboration, ArXiv:nucl-ex/0309004, submitted to Phys. Rev. Lett.] (see also R.G.H. Robertson's contribution to this conference). This background is, when combined with ex-situ methods, found to be 0.72 +0.24 -0.23 neutrons per day
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Salty neutrinos from the sun: Results from the salt phase of the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a 1 ktonne heavy-water Cerenkov detector. The first phase of this experiment has shown that neutrinos from the Sun change flavour. For the second phase of the experiment, approximately 2 tonnes of salt ( NaCl) was added to the heavy water to enhance the neutral-current detection as well as the neutral-current and charged-current separability. Here the results are presented from the complete salt phase at the Sudbury Neutrino Observatory. The electron energy spectrum is presented for the first time. It is consistent with an undistorted 8B spectral shape. It is also consistent with the Large Mixing Angle (LMA) parameters obtained through a global fit including the data presented in this paper. These parameters are found to be ?m2 = (8.0+0.6-0.4)×10-5eV^2 and ? = 33.9+2.4-2.2 degrees. The total flux of active-flavour neutrinos from 8B decay in the Sun is found to be 4.94+0.21-0.21(stat)+0.38-0.34(syst), whereas the integral flux of electron neutrinos for an undistorted 8B spectrum is 1.68+0.0.6-0.06(stat)+0.08-0.09(syst), both in units of 106cm^-2 s^-1. The day-night asymmetry in the observed fluxes is consistent with both absence of matter-enhancement effects in the Earth and with the small level of these effects expected for the LMA model as stated above
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Latest results from the Sudbury Neutrino Observatory
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Seeking theta(13) with reactor neutrinos
An overview of the hunt for the neutrino oscillation mixing parameter theta(13) using reactor neutrinos is given. A general overview of the design criteria of such experiments is presented, after which the current proposed experiments are shortly discussed. A comparison of the sensitivity experiments is made, together with other experiments with direct sensitivity to this parameter on a similar time scale
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Photon-counting computed tomography and scintillator-based detectors: a simulation analysis with scintillating and reflecting materials currently on the market
During the last decade, Photon-Counting Computed Tomography (PCCT) has been quickly developing and it is expected to revolutionize the X-ray imaging field. Rapid development has also been ongoing in the scintillator and photosensor fields: fast inorganic scintillators have become available on the market and the silicon photomultiplier (SiPM) technology has made substantial progress. Therefore, SiPM-based scintillator detectors may soon be successfully applied in challenging applications like PCCT. In this work, a simulation framework is developed to evaluate detectors composed of scintillators coupled to SiPMs. The idea is to combine Monte Carlo simulations and a library to generate SiPM signals. Focus is given to six fast inorganic scintillators currently on the market (Ce:LYSO, Ce:LuAP, Pr:LuAG, Ce:LuAG, Ce:GGAG (ceramic), Ce:GAGG (single crystal)) and different TiO2-epoxy mixtures. The main properties of scintillating and reflecting materials to be defined in the simulation database are characterised experimentally. Using a virtual model created within this framework, an analysis of the performance in PCCT of a SiPM-based scintillator detector composed of the considered materials is performed. Simulated pulses are processed to report on the count-rate capability. Among the studied crystals, Ce:LYSO would enable sustaining the highest rate of interacting X-ray (2.5 Mcps/pixel with 30% of pile-up). Ce:GAGG could also handle a rate ~ 1 Mcps/pixel with identical pile-up conditions. Other materials show a slow decay time in their scintillation kinetics, implicating a < 1 Mcps/pixel count rate. A qualitative evaluation of the energy binning efficiency is also accomplished, by defining this parameter as a quality metric for multiclass classification. Scintillators with high light yield and good energy resolution (Ce:LYSO, Ce:GAGG and Ce:GGAG) present the best energy binning performance, as expected. The dependence of this aspect is explored as a function of the pulse processing method used, the crystals size and the pile-up probability. Resulting trends respect predictions, even though for a more quantitative analysis a more in-depth study is required
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Large low background kTon-scale liquid argon time projection chambers
We find that it is possible to increase sensitivity to low energy physics in a third or fourth Deep Underground Neutrino Experiment (DUNE)-like module with careful controls over radiopurity and targeted modifications to a detector similar to the DUNE Far Detector design. In particular, sensitivity to supernova and solar neutrinos can be enhanced with improved MeV-scale reach. A neutrinoless double beta decay search with 136Xe loading appears feasible. Furthermore, sensitivity to Weakly-Interacting Massive Particle (WIMP) Dark Matter becomes competitive with the planned world program in such a detector, offering a unique seasonal variation detection that is characteristic of the nature of WIMPs.</p
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Precision measurement of the specific activity of 39 Ar in atmospheric argon with the DEAP-3600 detector
The specific activity of the β decay of 39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of 39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001 stat ± 0.024 sys) Bq/kg atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.</p
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Impact of cross-section uncertainties on supernova neutrino spectral parameter fitting in the Deep Underground Neutrino Experiment
A primary goal of the upcoming Deep Underground Neutrino Experiment (DUNE) is to measure the O(10) MeV neutrinos produced by a Galactic core-collapse supernova if one should occur during the lifetime of the experiment. The liquid-argon-based detectors planned for DUNE are expected to be uniquely sensitive to the νe component of the supernova flux, enabling a wide variety of physics and astrophysics measurements. A key requirement for a correct interpretation of these measurements is a good understanding of the energy-dependent total cross section σ(Eν) for charged-current νe absorption on argon. In the context of a simulated extraction of supernova νe spectral parameters from a toy analysis, we investigate the impact of σ(Eν) modeling uncertainties on DUNE's supernova neutrino physics sensitivity for the first time. We find that the currently large theoretical uncertainties on σ(Eν) must be substantially reduced before the νe flux parameters can be extracted reliably; in the absence of external constraints, a measurement of the integrated neutrino luminosity with less than 10% bias with DUNE requires σ(Eν) to be known to about 5%. The neutrino spectral shape parameters can be known to better than 10% for a 20% uncertainty on the cross-section scale, although they will be sensitive to uncertainties on the shape of σ(Eν). A direct measurement of low-energy νe-argon scattering would be invaluable for improving the theoretical precision to the needed level
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Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
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Reconstruction of interactions in the ProtoDUNE-SP detector with Pandora
The Pandora Software Development Kit and algorithm libraries provide pattern-recognition logic essential to the reconstruction of particle interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at ProtoDUNE-SP, a prototype for the Deep Underground Neutrino Experiment far detector. ProtoDUNE-SP, located at CERN, is exposed to a charged-particle test beam. This paper gives an overview of the Pandora reconstruction algorithms and how they have been tailored for use at ProtoDUNE-SP. In complex events with numerous cosmic-ray and beam background particles, the simulated reconstruction and identification efficiency for triggered test-beam particles is above 80% for the majority of particle type and beam momentum combinations. Specifically, simulated 1 GeV/c charged pions and protons are correctly reconstructed and identified with efficiencies of 86.1±0.6
% and 84.1±0.6
%, respectively. The efficiencies measured for test-beam data are shown to be within 5% of those predicted by the simulation