An Assessment of the Science Proposed for the Deep Underground Science and Engineering Laboratory (DUSEL) (2012) / Chapter Skim
Currently Skimming:
3 Science Assessments
3 Science Assessments
Pages 28-87
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 28... ...
The proposed physics experiments are one or more dark matter experiments; a longbaseline experiment for the study of neutrino oscillations and proton decay that is also capable of measurements in neutrino astrophysics; a neutrinoless doublebeta decay experiment; and an accelerator-based nuclear astrophysics experiment. Accordingly, the chapter assesses, in no particular order, the physics questions of dark matter, of long-baseline neutrino oscillations and neutrinoless double-betadecay in the larger context of neutrino physics and, together with proton decay, in the context of unified theories; of nuclear astrophysics, and of neutrino astrophysics.
|
From page 29... ...
In choosing to focus in this way, the committee intends its assessments to be of value to the future direction of underground research, independent of whether the DUSEL program, as presently conceived, is realized. Finally, the committee assessed the intellectual merit of the underground science of the proposed DUSEL program in the general context of frontier scientific research worldwide.
|
From page 30... ...
Scientific Landscape Theories of elementary particle physics provide natural candidates for WIMPs. For example, in many supersymmetric models, the lightest supersymmetric particle is stable, and many of these theories naturally provide particles with masses and interaction cross sections that are consistent with astronomical and cosmological bounds on WIMP properties.
|
From page 31... ...
. The interactions of familiar matter slow the collision, while the weakly interacting dark matter associated with each galaxy is essentially transparent and so passes through.
|
From page 32... ...
Therefore, detectors having a good likelihood of measuring such collisions would need to be large and operate deep underground to reduce backgrounds of cosmic ray origin that can mimic the signals being sought. These searches are based on the hypothesis that dark matter consists of WIMPs with a mass of a few tens of proton masses or greater.
|
From page 33... ...
To address these uncertainties about signals, it is important that a single experiment be able to collect multiple complementary signals and that multiple experiments using different nuclear targets are conducted. The most recent results over the WIMP mass range of 10-1,000 GeV exclude cross sections approaching 10-44 cm2 per nucleon for the simplest models (see Figure 3.2)
|
From page 34... ...
Russia Boulby, U.K. United States Darkside-50 Design 1 ton Design MAX S4, R&D 50 kg Ar DAr under Same 6 tons Xe 2017 Install LNGS procurement shield as 20 tons DAr 2011-2012 DarkSide-50 DUSEL United States/ XENON100 Running XENON1T Design Europe/ 80 kg 2.4 tons Xe 2012 Install China Gran Sasso United States/ SCDMS Construction SCDMS R&D GEODM S4, R&D Canada 10 kg Ge 2011 Install 100 kg Ge 2014 Install 1.5 tons 2018 Soudan SNOLAB DUSEL United States COUPP Construction 500 kg 2011 Design 16 ton scale S4 60 kg CF3 NUMI test 2013 Install R&D SNOLAB 2010 Canada PICASSO Running PICASSO II 2010/11 PICASSO III 2012/13 Install 2.6 kg 25 kg Install >500 kg SNOLAB United States/ MiniCLEAN Construction DEAP-3600 Funded CLEAN Planning Canada 500 kg Ar 2011 Install 3.6 tons 2012 Install 50 tons Ar/Ne R&D Europe Edelweiss Running EURECA Active R&D EURECA Planning Now 3 kg → 24 kg 100 kg Ge 2013 Install 1 ton Ge/ 2016 24 kg Ge funding interleaved Scintillator, 2011 Modane secured Ge/scintillator, LS Modane Modane extension Europe CRESST Running extension, 5 kg of CaWO4 Merging of Gran Sasso CRESST and Edelweiss Europe ArDM Construction 800 kg Ar 2011 Install Canfranc Europe/ WARP Running United States 140 kg Ar Gran Sasso
|
From page 35... ...
DAr, Ar depleted in 39Ar; LUX, Large Underground Xenon experiment; LZS, 1,500 to 3,000 kg liquid xenon detector; LZD, 20-ton liquid xenon detector; S4, NSF Solicitation 4; ZEPLIN III, two-phase Xe detector; Darkside, Depleted Argon [K] ryogenic Scintillation and Ionization Detector; MAX, Multiton Argon and Xenon detector; LNGS, Laboratori Nazionali del Gran Sasso; XENON100, Xenon 100-kg dark matter experiment; XENON1T, Xenon 1 ton dark matter experiment; SCDMS, Soudan Cryogenic Dark Matter Search; GEODM, Germanium Observatory for Dark Matter; COUPP, Chicago land Observatory for Underground Particle Physics; MiniCLEAN, Mini-Cryogenic Low Energy Astrophysics with Noble liquids experiment; DEAP-3600, Dark matter Experiment using Argon Pulse-shape discrimination; CLEAN, Cryogenic Low Energy Astrophysics with Noble liquids experiment; EURECA, European Underground Rare Event Calorimeter Array; CRESST, Cryogenic Rare Event Search with Superconducting Thermometers; ArDM, Argon Dark Matter experiment; WARP, Wimp Argon Program experiment; XMASS, Xenon Dark Matter Search Experiment.
|
From page 36... ...
An annual modulation signal would be compelling evidence and within the scope of a G2 or G3 experiment. Beyond annual modulation, a detector with directional sensitivity could poten tially observe a daily modulation of the direction of dark matter at all energies due
|
From page 37... ...
Conclusion: The direct detection dark matter underground experiment is of paramount scientific importance and will address a crucial question upon whose answer the tenets of our understanding of the Universe depend. This experiment would not only provide an exceptional opportunity to address a scientific question of paramount importance, it would also have a significant positive impact upon the stewardship of the particle physics and nuclear physics research communities and would have the United States assume a visible leadership role in the expanding field of underground science.
|
From page 38... ...
While installation of such a U.S.-developed experiment in an appropriate foreign facility would significantly benefit scientific progress and the research communities, there would be substantial advantages to the communities if this experiment could be installed within the United States, possibly at the same site as the long-baseline neutrino experiment. Tests of Grand Unification Theories The three other major physics experiments proposed for DUSEL -- neutrino oscillations, neutrinoless double-beta decay, and proton decay -- are among the most promising tests of theories that seek to provide a unified description of the forces.2 After providing a general overview of the nature of grand unification theo ries, these three experiments, and the roles they might play in resolving outstanding questions, are described.
|
From page 39... ...
The neu R02033 trinos are the only fermions without electric charge and so are the only matter particles that do not bitmapped raster, not editable consists of quarks (inside engage in electromagnetic interactions. Matter in the "visible" Universe protons, neutrons, and other nuclei)
|
From page 40... ...
and that neither lepton number nor lepton flavor would be conserved. In GUTs, baryon and lepton number violations are associated with the exchange of new, extremely heavy force carriers, with masses ~1015 times that of the proton, so that a process like proton decay exists but would be extremely rare.
|
From page 41... ...
GUTs offer a beautiful explanation for the origin of the asymmetry between matter and antimatter, which is deeply connected with CP violation in neutrino oscillations, tiny neutrino masses, and neutrino flavor change. In GUTs, the neutrino masses are inversely proportional to the masses of very heavy particles, so the tiny size of the neutrino masses suggests the existence of particles that are too heavy to be produced today but that could have been produced in the early Universe.
|
From page 42... ...
In the Standard Model of particle physics, neutrinos have a lepton number and antineutrinos have a lepton number of the opposite sign. Since lepton number is conserved in the Standard Model, neutrinos and antineutrinos are distinguishable and their differences can be studied through their interactions with matter.
|
From page 43... ...
The ideas of both massive and flavor-changing neutrinos were revolutionary, and because the experimental evidence was not strong, the Standard Model of particle physics was constructed with massless and flavor-conserving neutrinos. Only within the last 15 years has the experimental evidence for neutrino oscil lations become convincing enough for the scientific community to accept that they are a fact of nature.
|
From page 44... ...
• The hierarchy, or ordering, of the neutrino masses is contained in the signs of the linear mass differences. The sign of Δm21 is known, so the sign of 2 Δm322 completely determines this ordering.
|
From page 45... ...
Just as in more conventional particle physics, where initial observations of new particles in cosmic rays gave way to the controlled creation of new particles in accelerators, precision observations of neutrino oscillations must move from the now exploited natural sources to controlled high-flux accelerator-produced neutrinos. In this way, the K2K and MINOS experiments have already provided observations of muon neutrino disappearance, the NOVA experiment will operate in the next few years, and the new T2K experiments are just beginning to produce results in a search for electron appearance in a muon neutrino beam.
|
From page 46... ...
This is a key question, since observing CP violation in neutrino oscillations would open a new window into the physics of matter and anti matter, providing essential inputs into models of leptogenesis, discussed more fully in the section on proton decay.
|
From page 47... ...
In order to eliminate backgrounds from cosmic ray events, it must be located underground. An experiment with such capabilities -- the LBNE -- will allow, in addition to the search for CP violation, a broad program of neutrino physics, as well as sensitivity to proton decay.
|
From page 48... ...
It would also significantly impact the interpretation of the sensitivity of any double-beta decay experiments. The main goal of LBNE is to significantly extend our sensitivity to the neu trino oscillation parameters over existing experiments using a broad-band neu trino beam (a beam with a wide range of neutrino energies)
|
From page 49... ...
The development and operation of the MicroBOONE 800-ton LAr experiment at Fermilab will be a first step in resolving many of these technical issues. From the point of view of neutrino oscillations alone, the physics sensitivity of the water Cherenkov module and the LAr options are similar.
|
From page 50... ...
With the same kind of water Cherenkov detector, the statistical improvement would be at best nominal, by a factor of, say, 2 or 3. Although an alternative LAr detector of lower tonnage would provide less statistical improvement, it might be able to make a more definitive observation of tau neutrinos produced from oscillated cosmic ray muon neutrinos.
|
From page 51... ...
The U.S. par ticle physics program is especially well positioned to build a world-leading long-baseline neutrino experiment due to the combined availability of an intense neutrino beam from Fermilab and a suitably long baseline from the neutrino source to an appropriate underground site such as the proposed DUSEL.
|
From page 52... ...
Establishing that neutrinos are Majorana particles would have a number of important consequences. Because 0nbb decay rates depend on neutrino masses, determining those rates would be the most sensitive laboratory experiment to determine the neutrino mass scale.
|
From page 53... ...
. If oscillation experiments demonstrate that the mass hierarchy of neutrinos is inverted, then having 0nbb decay results establish an upper limit of 20 meV on the effective Majorana neutrino mass would show that neutrinos are not Majorana particles (see Figure 3.5)
|
From page 54... ...
Knowledge of the absolute mass scale is needed in order to understand neutrino masses within the framework of particle physics, as well as to gauge the impact that massive neutrinos have on cosmology. Neutrino oscillation experiments cannot determine the absolute mass scale (only the squared mass differences)
|
From page 55... ...
Those experiments use several key experimental detection techniques, such as calorimetric bolometers (e.g., CUORICINO and CUORE at Gran Sasso) , cryogenic semiconductor detectors (e.g., GERDA at Gran Sasso and MAJORANA at the Sanford Underground Laboratory)
|
From page 56... ...
within 10 years. The latter can probe most of the phase space permitted by the inverted hierarchy spectrum of neutrino masses.
|
From page 57... ...
scientists be supported to participate in other such experiments worldwide. Conclusion: The neutrinoless double-beta decay experiment, like the direct detection dark matter experiment and the long-baseline neutrino oscillation experiment, is of paramount scientific importance and will address crucial 11 H.V.
|
From page 58... ...
While installation of such a U.S.-developed experiment in an appropriate foreign facility would significantly benefit scientific progress and the research communities, there would be substantial advantages to the communities if this experiment could be installed within the United States, possibly at the same site as the long baseline neutrino experiment. Proton Decay Overview Atoms are made of electrons and nuclei and nuclei are made of protons and neutrons.
|
From page 59... ...
However, all unified models predict that the proton does decay, and proton decay remains the main unverified prediction of unification, which has other successes. These successes include agreement with the measured weak interaction mixing angle discussed above and, importantly, the presence of small but nonzero neutrino masses and of neutrino oscillations.
|
From page 60... ...
The impact of depth underground on background rates has been studied,13 leading to the conclusion that with an active muon veto shield, a proton decay search may be viable at fairly shallow_depths for both water Cherenkov and LAr detectors. However, for the p → K+ + ν mode, expected background due to cosmic ray interactions in the rock near the detector can be eliminated only by limiting the fiducial volume to the central region of the detector volume.
|
From page 61... ...
2010. Review of particle physics, Journal of Physics G-Nuclear and Particle Physics 37: 075021.
|
From page 62... ...
Each of the two detector technology options offers some, but different, promise for increased sensitivity to proton decay. Conclusion: The stability of the proton is a crucial, fundamental scientific question and can be studied by the large underground detector of a long 15 M
|
From page 63... ...
However, the sensitivity is not so important as to make the search for proton decay the primary consideration in choosing neutrino detector technology or a site for the experiment. Nuclear Astrophysics Overview Understanding nuclear processes is critical to interpreting a number of astrophysical observations that range from stellar energy generation and the formation of solar neutrinos to elemental and isotopic abundances of the elements in the Universe.
|
From page 64... ...
the production of vector formation, elements heavier than iron in neutron-rich nucleosynthesis. Each of these processes requires improved measurements of low-energy nuclear cross sections.
|
From page 65... ...
These three science topics are among the most compelling in the field of nuclear astrophysics, which itself was noted as being one of three key intellectual directions for nuclear physics in the 2007 long-range plan for nuclear physics.17 The main thrusts within nuclear astrophysics are exploring the structure of nuclei far from stability, understanding the nuclear equation of state, and measurements of low-energy nuclear cross sections. The first two thrusts are key elements of the new facility for rare isotope beams (FRIB)
|
From page 66... ...
The proposed DIANA facility consists of two high-current accelerators (about 100 times the luminosity of LUNA) , whose beams can be directed to a number of target stations.
|
From page 67... ...
Clearly, a significant portion of the international community is interested in the science of low-energy nuclear astrophysics. As discussed above, in addition to the LUNA facility at Gran Sasso (3,500 m.w.e.)
|
From page 68... ...
The LUNA facility at Gran Sasso has already demonstrated the usefulness of an underground accelerator for understanding the hydrogen burning process. A more advanced facility such as DIANA will shed light on other key burning processes in stars and on the production of elements heavier than iron.
|
From page 69... ...
However, the present and upcoming generation of large underground detectors hopefully will increase our neutrino source catalog to include a galactic supernova, the integrated flux of all supernovas throughout the history of the Universe, ultra-high-energy sources such as active galactic nuclei and gamma-ray bursts, and even Earth itself. Scientific Landscape -- Neutrino Astrophysics Supernovas are spectacular stellar explosions in which the energy released in a few weeks is comparable to that expended by the Sun during its entire lifetime.
|
From page 70... ...
However, to estimate the expected neutrino signal at Earth from a galactic supernova, flavor oscillations must be taken into account and, in fact, the detected neutrino signal can provide crucial information about not only supernovas but also the neutrino. The detection of 19 neutrinos from SN1987A in the Large Magellanic Cloud by the first generation of underground water Cherenkov detectors at Kamiokande in Japan and the onetime Irvine-Michigan-Brookhaven detector was a historic event that demonstrated the possibility of supernova neutrino astronomy.
|
From page 71... ...
. The reduction by more than an order of magnitude in the neutrino signal in the LAr detector relative to the water Cherenkov detector is due partly to its smaller size and partly to the relevant interaction cross sections.
|
From page 72... ...
Conclusion: Neutrinos from supernovas can be studied by a large under ground detector of a long-baseline neutrino experiment, making a unique and valuable contribution to our understanding of one of the most impor tant astrophysical phenomena. This capability of the neutrino oscillation experiment would be of great scientific interest and add a significant value to that experiment.
|
From page 73... ...
Subsurface engineering research includes work related to fairly traditional extractive activities that arise in petroleum drilling and mining and civil engineering issues associated with rock slopes, dam foundations, tunnels, rapid transit, and subsurface city infrastructure. However, those more traditional research fields are now joined by research in areas such as "enhanced" geothermal systems, unconventional sources of natural gas, and an ever-widening variety of applications of the subsurface for isolating materials such as nuclear waste and CO2.
|
From page 74... ...
. In the interior of a rock mass, the rock remains "elastic" but may still undergo long-term strength changes owing to the thermochemical effects of the fluids circulating through the rock.
|
From page 75... ...
Deformation Complete Load-Deformation Behavior FIGURE 3.9 Effects of size and timescales on the mechanical response of rock to applied loads. The quotation, from a pioneer and professor of subsurface engineering, Leopold Müller, referred to the central challenge of rock mechanics.
|
From page 76... ...
For example, well bores that target large faults can provide rock samples to support physical and chemical investigations of earthquake zones.22 Nevertheless, for assessing other important attributes of rocks in these set tings -- fractures and faults and their relations to fluids, in situ stress, chemical reactions and microbiology -- wellbore-based studies have important limitations. Data are commonly incomplete because meaningful samples of subsurface fracture networks are inherently difficult if not impossible to obtain.
|
From page 77... ...
Moreover, these fossilized records lack the essential dynamic context of tectonic, burial, and thermal loading, fluid flow, and chemical reactions. Faults are important features that cross a wide spectrum of the geosciences and have important societal impacts beyond earthquakes.
|
From page 78... ...
Any disturbance of the subsurface, be it "natural" -- for instance by volcanic or seismic activity -- or as a result of engineering, will change the preexisting 28 Active experiments, such as placing heaters in the rock mass, might improve our understanding of how coupled mechanical, chemical, and fluid-flow behavior responds to environmental changes.
|
From page 79... ...
In some cases, the behavior of cores, the primary basis for much of university laboratory rock mechanics research to date, may not be representative of rock's behavior in situ. Bioscience Challenges Microorganisms have inhabited Earth for 3.5 billion years and hence have had a much longer time for adapting to life in a mineral world than some more recent microorganisms have had to adapt to life with higher organisms.
|
From page 80... ...
The rupture process itself may release hydrogen, carbon, or other compounds that go on to take part in chemical and biochemical reactions. Limitations All existing and proposed underground facilities have important limitations, especially for subsurface engineering and geoscience research.
|
From page 81... ...
Biosciences Scale Effects and Coupled Processes Much of the research intended in this category was stimulated by the proposal to construct the large water Cherenkov cavity (~60 m span) at a depth of 1.5 km (4,850 ft)
|
From page 82... ...
Yow and J.R. Hunt, Coupled processes in rock mass performance with emphasis on nuclear waste isolation, International Journal of Rock Mechanics and Mining Sciences, 39 (2)
|
From page 83... ...
Other important methods of inducing fracturing include use of explosives and rock-cutting tools in tunnel boring machines, all in an effort to increase drilling rates in deep borehole drilling.32 A study has been proposed to conduct hydraulic fracturing tests in a rock block similar in dimension to the heated block test discussed in the preceding section. Instrumentation would be installed to detect microseismic activity and velocity changes during fracture propagation.
|
From page 84... ...
.33 If forces on faults are in a state of critical equilibrium the implications for engineering operations that disturb this equilibrium are profound.34 A deep underground laboratory could allow measurements of rock strain as a function of time and position near faults and in the rock mass. These data would help explain the influence of geology and human activity on strain and stress distribution in rock, allow observation of how deforma tion accumulates near faults and fractures, and provide insights into how laboratory and underground laboratory measurements of fault slip processes can be scaled to larger events.
|
From page 85... ...
defining the depth of the biosphere and (2) determining whether some unique biology exists in terms of energy sources, physiology, and evolutionary outcomes, including life as we do not know it.
|
From page 86... ...
Fracture Network Engineering The development and control of fracture networks at depth by remote stimula tion of a rock mass is central to many aspects of subsurface engineering. Currently, although hydraulic fracturing is a major component of oil and natural resource development, it is still in some respects more art than science.
|
From page 87... ...
Conclusion: The ability to perform long-term experiments in the regulated environment of an underground research facility could enable a paradigm shift in research in subsurface engineering and would allow other valuable experiments in the geosciences and biosciences. 37 The events in Japan resulting from the devastating earthquake in 2011 have reopened discussion of underground location of nuclear reactors to avoid the possibility of releases of dangerous concentrations of radionuclides into the atmosphere.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.