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Author: Melinda Dominique Sweany Publisher: ISBN: 9781267029393 Category : Languages : en Pages :
Book Description
Direct dark matter experiments generally cannot distinguish between nuclear recoils caused by Weakly Interacting Massive Particles (WIMPs) and those caused by neutron backgrounds. It is therefore crucial that all sources of neutron background are well understood and accounted for when claiming a discovery or reporting limits on the WIMP-nucleon cross section. One source of neutrons that is not well understood results from cosmogenic muon interactions in the material surrounding a detector. The Neutron Multiplicity Meter in the Soudan cavern is a gadolinium-doped water Cherenkov detector capable of detecting high multiplicity neutron showers resulting from fast neutrons incident on a lead target. This measurement is the first such measurement obtained without a liquid scintillator detector medium; muon and neutron spallation is media-dependent, and because neutron shield technology for dark matter detectors is moving towards water, this is an important measurement. The integrated fast neutron flux in the Soudan cavern is reported as a linear function of the power, [alpha], of the neutron angular distribution with the zenith angle: [Fourier transform] = 4.8x10−9 ± 3.5x10−10 + (5.4x10−10 ± 1.5x10−10)[alpha]. Technological studies of neutron detection with gadolinium-doped water are also reported here. The neutron detection efficiency of a cylindrical 3.5 kL detector is measured at 70% for neutrons in the center of the detector. In addition, other improvements to water Cherenkov technology are explored, namely the addition of water-soluble wavelength-shifting chemicals. The wavelength-shifting chemical 4-Methylumbelliferone has been shown here to increase the measured light output of Cherenkov radiation resulting from neutron capture showers by a factor of 1.7.
Author: Melinda Dominique Sweany Publisher: ISBN: 9781267029393 Category : Languages : en Pages :
Book Description
Direct dark matter experiments generally cannot distinguish between nuclear recoils caused by Weakly Interacting Massive Particles (WIMPs) and those caused by neutron backgrounds. It is therefore crucial that all sources of neutron background are well understood and accounted for when claiming a discovery or reporting limits on the WIMP-nucleon cross section. One source of neutrons that is not well understood results from cosmogenic muon interactions in the material surrounding a detector. The Neutron Multiplicity Meter in the Soudan cavern is a gadolinium-doped water Cherenkov detector capable of detecting high multiplicity neutron showers resulting from fast neutrons incident on a lead target. This measurement is the first such measurement obtained without a liquid scintillator detector medium; muon and neutron spallation is media-dependent, and because neutron shield technology for dark matter detectors is moving towards water, this is an important measurement. The integrated fast neutron flux in the Soudan cavern is reported as a linear function of the power, [alpha], of the neutron angular distribution with the zenith angle: [Fourier transform] = 4.8x10−9 ± 3.5x10−10 + (5.4x10−10 ± 1.5x10−10)[alpha]. Technological studies of neutron detection with gadolinium-doped water are also reported here. The neutron detection efficiency of a cylindrical 3.5 kL detector is measured at 70% for neutrons in the center of the detector. In addition, other improvements to water Cherenkov technology are explored, namely the addition of water-soluble wavelength-shifting chemicals. The wavelength-shifting chemical 4-Methylumbelliferone has been shown here to increase the measured light output of Cherenkov radiation resulting from neutron capture showers by a factor of 1.7.
Author: Publisher: ISBN: Category : Languages : en Pages : 194
Book Description
Direct dark matter detection experiments usually have excellent capability to distinguish nuclear recoils, expected interactions with Weakly Interacting Massive Particle (WIMP) dark matter, and electronic recoils, so that they can efficiently reject background events such as gamma-rays and charged particles. However, both WIMPs and neutrons can induce nuclear recoils. Neutrons are then the most crucial background for direct dark matter detection. It is important to understand and account for all sources of neutron backgrounds when claiming a discovery of dark matter detection or reporting limits on the WIMP-nucleon cross section. One type of neutron background that is not well understood is the cosmogenic neutrons from muons interacting with the underground cavern rock and materials surrounding a dark matter detector. The Neutron Multiplicity Meter (NMM) is a water Cherenkov detector capable of measuring the cosmogenic neutron flux at the Soudan Underground Laboratory, which has an overburden of 2090 meters water equivalent. The NMM consists of two 2.2-tonne gadolinium-doped water tanks situated atop a 20-tonne lead target. It detects a high-energy (>~ 50 MeV) neutron via moderation and capture of the multiple secondary neutrons released when the former interacts in the lead target. The multiplicity of secondary neutrons for the high-energy neutron provides a benchmark for comparison to the current Monte Carlo predictions. Combining with the Monte Carlo simulation, the muon-induced high-energy neutron flux above 50 MeV is measured to be (1.3 ± 0.2) ~ 10-9 cm-2s-1, in reasonable agreement with the model prediction. The measured multiplicity spectrum agrees well with that of Monte Carlo simulation for multiplicity below 10, but shows an excess of approximately a factor of three over Monte Carlo prediction for multiplicities ~ 10 - 20. In an effort to reduce neutron backgrounds for the dark matter experiment SuperCDMS SNO- LAB, an active neutron veto was developed. It is estimated that the current design of the neutron veto with a 40 cm thick layer of boron-doped liquid scintillator can achieve a> 90% efficiency for tagging the single-scatter neutrons. In addition, a one-quarter scale prototype detector for neutron veto has been built and tested.
Author: Elena Aprile Publisher: John Wiley & Sons ISBN: 3527609636 Category : Science Languages : en Pages : 362
Book Description
This book discusses the physical properties of noble fluids, operational principles of detectors based on these media, and the best technical solutions to the design of these detectors. Essential attention is given to detector technology: purification methods and monitoring of purity, information readout methods, electronics, detection of hard ultra-violet light emission, selection of materials, cryogenics etc. The book is mostly addressed to physicists and graduate students involved in the preparation of fundamental next generation experiments, nuclear engineers developing instrumentation for national nuclear security and for monitoring nuclear materials.
Author: David Samuel Blum Publisher: ISBN: Category : Languages : en Pages :
Book Description
Extensive evidence from various astrophysical observations suggests that most of the matter in the universe is dark matter. However, the nature of dark matter is still unknown and remains one of the most prominent unanswered questions in physics today. A potential way to search for dark matter is the indirect dark matter search with neutrinos. It is based on the hypothesis that dark matter particles self-annihilate into neutrinos. This would result in a neutrino flux, which could be measured by neutrino detectors at Earth. In case of no excess signal is observed, a limit on the dark matter self-annihilation cross section can be set. The future neutrino detectors JUNO and THEIA can search for dark matter, especially for light dark matter particles with masses ranging from MeV to GeV. The search for such light dark matter particles has gained in importance in the last years as it extends the typical WIMP search to the sub-GeV mass range. In this work, the sensitivities of JUNO and THEIA to measure neutrinos from dark matter self-annihilation in the Milky Way as an excess over backgrounds are determined in detail for the first time. The work focuses on direct self-annihilation of light dark matter particles with masses ranging from 15 MeV to 100 MeV into neutrino-antineutrino pairs. The expected electron antineutrino signal measured through the inverse beta decay (IBD) reaction and all background contributions occurring in the visible energy region from 10 MeV to 100 MeV are determined for both detectors. To effectively reduce IBD-like background events of atmospheric neutrinos interacting via neutral current and of fast neutrons in JUNO, pulse shape discrimination is studied and applied in this work. THEIA would feature the separate measurement of Cherenkov and scintillation light. As a consequence, selection cuts on the ratio of measured Cherenkov to scintillation light and on the number of reconstructed Cherenkov rings are determined in this work, which can suppress atmospheric neutral current and fast neutron background events in THEIA with high efficiency. The sensitivities of JUNO and THEIA are determined using a Bayesian analysis and Markov Chain Monte Carlo sampling for dark matter masses ranging from 15 MeV to 100 MeV. JUNO will achieve the highest sensitivity for indirect dark matter search with neutrinos among existing neutrino detectors and will take a leading role in the indirect dark matter search in the upcoming years. The results of this work show for the first time that JUNO will improve the best currently existing 90 % C.L. upper limit of neutrino detectors on the dark matter self-annihilation cross section by a factor of 2 to 9 for 10 years of data taking. JUNO's potential to discover an electron antineutrino signal from dark matter self-annihilation in the Milky Way as an excess over backgrounds will be between 3 sigma and 5 sigma for most dark matter masses from 15 MeV to 100 MeV assuming an annihilation cross section that corresponds to the 90 % C.L. upper limit on the annihilation cross section of Super-K. This work moreover demonstrates that THEIA, if realized, could achieve a sensitivity comparable to JUNO.
Author: Steven James Sutherland Plank Publisher: ISBN: Category : Dark matter (Astronomy) Languages : en Pages : 211
Book Description
It is now largely accepted that dark matter, and more specifically, Weakly Interacting Massive Particles (WIMPs), constitute the majority of the mass in our Universe. Within this thesis are presented: (i) an overview of the motivation and evidence for the existence of dark matter; (ii) a detailed discussion of direct detection techniques and a worldwide review of WIMP search experiments; and (iii) new experimental measurements and complementary detailed numerical simulations, carried out by the author, to determine the performance of DRIFT experimental technology. Collectively, this work explores the capability of DRIFT technology to detect dark matter, and in doing so, to resolve one of the key open questions of contemporary science. The DRIFT programme consists of an array of direct dark matter search detectors located in the Boulby mine. An important limitation to the experiment is the neutron and gamma-ray background. Experimental work presented here has determined the U and Th content of the cavern rock to be 66±6 ppb and 145±13 ppb respectively, clarifying ambiguities in previous estimations. Through the use of a Monte Carlo simulation the neutron and gamma-ray background experienced by DRIFT has been determined and the experimental implications assessed. In addition, the activity of the main neutron calibration source used to calibrate DRIFT modules has been measured and was found to be 11600 n s-1±5% on the date of exposure, resolving an earlier discrepancy. Analysis of experimental data has confirmed that the technology employed by DRIFT detectors has the capability to provide directional information of recoiling nuclei at the low energies of interest to dark matter searches. A Monte Carlo simulation has then been employed to determine the WIMP-nucleon sensitivity achievable using DRIFT detectors of the present performance, also examining what would be achievable if this was supplemented by a realistic active neutron veto detector. It is found that a CS2-filled DRIFT type detector running at a 500 NIP threshold ( 16 keV and 27 keV for C and S recoils respectively) for 300 kg years, and surrounded by the proposed veto scheme, would expect to observe a background of six un-vetoed events. The minimum positive signal above this background (90% C.L.) would correspond to a WIMP-nucleon sensitivity limit of 1.75×10-9 pb. This identifies the realistic limit of what can be achieved using gaseous CS2 as a target medium. An investigation into the limits achievable using a similar array in which DRIFT modules act as self-vetoing detectors is also examined providing insight into the future development and operation of the DRIFT programme.
Author: Drew Anthony Fustin Publisher: ISBN: 9781267247117 Category : Languages : en Pages : 224
Book Description
The COUPP 4 kg bubble chamber employs 4.0 kg of CF3I as a WIMP scattering target for use as a dark matter direct detection search. This thesis reports the first experimental results from operating this bubble chamber at the deep underground site (6000 m.w.e.) of SNO-LAB, near Sudbury, Ontario. Twenty dark matter candidate events were observed during an effective exposure of 553.0 kg-days, when operating the bubble chamber at three different bubble nucleation thresholds. These data are consistent with a neutron background internal to the detector. Characterization of this neutron background has led to the recommendation to replace two detector components to maximize dark matter signal sensitivity in a future run with this bubble chamber. Measurement of the gamma-ray flux has confirmed that this detector should not be sensitive to a gamma-induced background for more than three orders of magnitude below current sensitivity. The dark matter search data presented here set a new world-leading limit on the spin-dependent WIMP-proton scattering cross section and demonstrate significant sensitivity to spin-independent WIMP-nucleon scattering.
Author: Neil J C Spooner Publisher: World Scientific ISBN: 9814480304 Category : Science Languages : en Pages : 685
Book Description
The prestigious Identification of Dark Matter workshop series was initiated to assess the status of work that attempts to identify the constitution of dark matter. In particular, it aims to review the success of current methods that are used in the search for dark matter, as well as the new techniques that are likely to improve prospects for detecting possible dark matter candidates in the future. In the 5th International Workshop, special emphasis was placed on the recent results obtained in experiments searching for baryonic and non-baryonic dark matter. This volume comprises the high-quality review articles and papers contributed by leaders and promising young physicists who attended the conference. It provides the most recent updates on dark matter searches from both experimental and theoretical points of view.The proceedings have been selected for coverage in:• Index to Scientific & Technical Proceedings® (ISTP® / ISI Proceedings)• Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)• CC Proceedings — Engineering & Physical Sciences
Author: Melinda Dominique Sweany
Author: Melinda Dominique Sweany
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Author: 
Author: Gianmarco Bruno
Author: Elena Aprile
Author: David Samuel Blum
Author: Jennifer Ceinwen Davies
Author: Steven James Sutherland Plank
Author: Drew Anthony Fustin
Author: Neil J C Spooner