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61-860: The LUX experiment, which cost approximately $ 10 million to build, was located 1,510 m (4,950 ft) underground at the Sanford Underground Laboratory (SURF, formerly the Deep Underground Science and Engineering Laboratory, or DUSEL) in the Homestake Mine (South Dakota) in Lead, South Dakota . The detector was located in the Davis campus, former site of the Nobel Prize-winning Homestake neutrino experiment led by Raymond Davis . It

122-532: A dual-phase xenon time projection chamber (TPC) . This detector is the target for WIMP-nucleus scatters. As discussed in the next section, this detector can perform a 3-D reconstruction of the position of an interaction in the xenon. This enables an identification and rejection of background interactions that happen near the periphery (sides, top, and bottom) of the detector. These peripheral interactions are overwhelmingly likely to be from external gamma rays or neutrons and radioactive decays of trace radionuclides in

183-764: A pioneer in neutrino research, built a solar neutrino detector deep underground at Sanford Lab. When he discovered only a third of what had been predicted, he inadvertently created what came to be called the “solar neutrino problem.” Other experiments— Sudbury Neutrino Observatory in Canada and the Super Kamiokande in Japan—vindicated Davis's work, earning him a one-fourth share of the Nobel Prize in Physics in 2002. The Education and Outreach program

244-584: A preprint, were published in Physical Review Letters , excluding cross sections above 9.2 × 10 cm at 36 GeV with 90% confidence level, jointly on the same date XENONnT published its first results too excluding cross sections above 2.58 × 10 cm at 28 GeV with 90% confidence level. As of 26 August 2024 , the Experiment had worked for 280 days (with the aim of 1,000 days) without finding evidence of 'dark matter', but tightening

305-462: A quiet inner fiducial volume for sensitive WIMP searches. It also enables discrimination between WIMP-like single-site interactions and background-like multi-site interactions, like those from neutrons or gamma rays. Note that unlike other kinds of time projection chambers, such as those used in neutrino experiments like MicroBooNE , the ionization signal here is fully captured via the S2 light - no current

366-560: A variety of disciplines. The facility is managed by Black Hills State University and houses five operational LBCs. These LBCs use germanium detectors housed in lead brick containers to screen materials, identifying ionizing radiation released by a material over time as its radioactive elements decay. This counting process helps researchers decide which types of materials are best-suited for their experiments. It also provides data to researchers, allowing them to calculate how much radioactivity they can expect to see coming from their materials over

427-531: A vast majority of them before they have the chance to enter the TPC. The whole assembly is located approximately one mile underground, in the Davis Cavern at SURF. This underground location creates a rock overburden that significantly reduces the rate of cosmic ray muons entering the TPC relative to the rate at Earth's surface. All together these different strategies ensure that LZ is a detector capable of performing

488-438: A very sensitive search for dark matter scatters on xenon nuclei. The detector at the heart of LZ is a cylindrical dual-phase xenon time projection chamber (TPC). This is composed of a 7 tonne liquid xenon target and a small region of gaseous xenon above. The operational principle is as follows. When a WIMP or background scatter occurs, a small amount of kinetic energy is given to a xenon nucleus (or atomic electron). This causes

549-730: A water-deionization system, cleanroom and control room for researchers. The researchers outfitted the Davis Cavern with a xenon purification system, servers, electronics and the experiment itself. All these are in service once again for the next-generation dark matter experiment, LUX-ZEPLIN (LZ). On the 4850 Level, the Black Hills State University Underground Campus (BHUC) houses Sanford Lab's low-background counting facility—a class-1,000 cleanroom containing several ultra-sensitive low background counters (LBCs) used to assay materials for ultra-sensitive experiments—and an adjoining workspace can be used for

610-507: Is a 780 square-foot laboratory with a class-1000 clean room. This laboratory provides space for researchers to clean and assemble parts of their experiments, before transporting them underground. To accommodate these processes, the SAL includes aluminum sheeting; air locks; a hoist; a 12-foot-deep pit for large assembly projects; and a radon-reduction system. Since Sanford Lab began operating in 2008, billions of gallons of water have been treated at

671-464: Is a collaborative venture between Sanford Lab and Black Hills State University (BHSU). The program provides resources for regional educators including 9 assembly programs, 13 curriculum modules and 12 field trips in an effort to promote STEM education. Sanford Lab also hosts public outreach events, including Deep Talks Science for Everyone series and a city-wide science festival, Neutrino Day, which draws 1,500 attendees annually. While public tours of

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732-687: Is a next-generation dark matter direct detection experiment hoping to observe weakly interacting massive particles (WIMP) scatters on nuclei. It was formed in 2012 by combining the LUX and ZEPLIN groups. It is currently a collaboration of 30 institutes in the US , UK , Portugal and South Korea . The experiment is located at about 1,500 metres under the Sanford Underground Research Facility (SURF) in South Dakota , and

793-567: Is an underground laboratory in Lead, South Dakota . The deepest underground laboratory in the United States, it houses multiple experiments in areas such as dark matter and neutrino physics research, biology, geology and engineering. There are currently 28 active research projects housed within the facility. Sanford Lab is managed by the South Dakota Science and Technology Authority (SDSTA). SURF operations are funded by

854-686: Is developing a deep seismic observatory for scientific investigations, sensor technology development and safety at the Sanford Lab. LUX: In May 2016, the Large Underground Xenon experiment (LUX) completed its experimental run. Although it didn't detect dark matter, it was declared the most sensitive dark matter detector in the world at the time. kISMET: The kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) drilled and cored five 50-meter deep boreholes to learn more about rock structure. The experiment

915-484: Is directly measured by electrodes. In July 2022, the LZ collaboration published in a preprint its first upper limit on the spin-independent WIMP-nucleon scattering cross section, using approximately 60 live days worth of data. Future searches intend to further probe for WIMP scatters, with a nominal search period of 1000 days. On 28 July 2023, the LZ experiment's first results of its searches for WIMPs, previously released as

976-529: Is managed by the United States Department of Energy 's (DOE) Lawrence Berkeley National Lab (Berkeley Lab). The experiment uses an ultra-sensitive detector made of 7 tonnes of liquid xenon to hunt for signals of WIMP-nucleus interactions. It is one of three such experiments which lead the search for direct detection of WIMPs above 10 GeV/c , the other two being the XENONnT experiment and

1037-414: Is particularly important for neutrons, which can penetrate farther than gamma rays and which scatter on the xenon nucleus in the same way that WIMPs are expected to (instead of on xenon's atomic electrons). The outer-detector PMT array is located in a larger water tank. Together, the water tank and liquid scintillator also provide significant passive shielding against external gamma rays and neutrons, stopping

1098-401: Is so quiet, this innermost, or "fiducial" volume is very sensitive to observing WIMP scatters above other backgrounds, and is the space in which LZ's WIMP searches are conducted. Next, the TPC is located inside several layers of active and passive shielding to reduce rates of external gamma rays and neutrons. The TPC is housed in an inner cryostat, which maintains the temperatures needed to keep

1159-722: The PANDAX -4T experiment. In the spring of 2015, LZ passed the "Critical Decision Step 1" or CD-1 review, and became an official DOE project. U.S. Department of Energy officials on Sept. 21, 2020 formally signed off on project completion for LZ; DOE's project completion milestone is called Critical Decision 4, or CD-4. To conclusively identify WIMP-nucleus scatters, LZ must be able to observe very small energy depositions in its active volume. However, it must also be able to differentiate true WIMP scatters from other interactions caused by bias. Examples of these known "backgrounds" are interactions from gamma rays produced by trace radioactivity in

1220-518: The U.S. Department of Energy through Fermi National Accelerator Laboratory and through a $ 70M donation from T. Denny Sanford . The State of South Dakota also contributed nearly $ 70 million to the project. Sanford Lab's depth, rock stability and history make it ideal for sensitive physics experiments that need to escape high energy cosmic radiation from the sun. Additionally, the facility is used for researchers studying geology, biology and engineering. DUNE , LBNF/hosted by Fermilab: Scientists with

1281-581: The 4850 Level, the average rock overburden is approximately 4,300 meters water equivalent (m.w.e.). This depth provides significant protection from cosmic radiation from the sun for sensitive particle physics experiments. Two main underground campuses, the Davis Campus and the Ross Campus, host experiments on the 4850 Level. Within the Davis Campus is the Davis Cavern, which originally housed Dr. Raymond Davis Jr.'s Solar Neutrino Experiment and

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1342-412: The 7-ton LUX-ZEPLIN has been approved, expected to begin in 2020. Initial unblinded data taken April to August 2013 were announced on October 30, 2013. In an 85 live-day run with 118 kg fiducial volume, LUX obtained 160 events passing the data analysis selection criteria, all consistent with electron recoil backgrounds. A profile likelihood statistical approach shows this result is consistent with

1403-569: The Davis experiment, allowed Raymond Davis, Jr. to measure the flux of solar neutrinos directly. The measurements' discrepancy with the flux predicted from the Sun 's luminosity led to Davis's development of the solar neutrino problem . The Homestake experiment publicized the mine as a resource among scientific communities. When the Homestake Mine closed in 2002, the National Science Foundation (NSF) had already considered

1464-662: The Deep Underground Gravity Laboratory used 20 seismometers strategically placed on the surface and on several levels of Sanford Lab from the 300 to the 485 Levels. Placed in a grid, the seismometers monitored ground motion , giving researchers a 3-Dimensional seismic picture that was used to inform the design of future gravitational wave detectors. DUGL, which was decommissioned in 2017, was a Laser Interferometer Gravitational-Wave Observatory ( LIGO ) related project. Solar Neutrino Experiment (Davis Experiment/Homestake Experiment): Raymond Davis Jr .,

1525-587: The Deep Underground Neutrino Experiment (DUNE) collaboration held a groundbreaking on the 4850 Level of Sanford Lab to mark the start of excavation for the Long-Baseline Neutrino Facility, which will host the international DUNE experiment. 44°21′07″N 103°45′04″W  /  44.352°N 103.751°W  / 44.352; -103.751 LZ experiment The LUX-ZEPLIN (LZ) Experiment

1586-548: The Deep Underground Neutrino Experiment (DUNE) hope to revolutionize our understanding of the role neutrinos play in the creation of the universe. The Long-Baseline Neutrino Facility (LBNF) will shoot a beam of neutrinos from Fermilab in Batavia, Illinois, 800 miles through the earth to detectors deep underground at Sanford Lab in Lead, South Dakota. LUX-Zeplin : LUX-ZEPLIN (LZ) is a next-generation dark matter detector that replaced

1647-474: The LUX experiment deep underground at Sanford Lab. The experiment continues the search for WIMPs (Weakly Interacting Massive Particles) using a detector that is 30 times larger and 100 times more sensitive than LUX. CASPAR: The Compact Accelerator System for Performing Astrophysical Research (CASPAR) collaboration uses a low-energy accelerator (50 foot long) to better understand how chemical elements are produced in

1708-582: The Lawrence Berkeley National Laboratory, agreed to support science operations at the lab. Today, Sanford Lab operations are funded by the U.S. Department of Energy through Fermi National Accelerator Laboratory . The first two major physics experiments located on the 4850 Level were the Large Underground Xenon (LUX) experiment and the Majorana Demonstrator experiment. LUX is housed in the same cavern that

1769-517: The SDSTA for use as a dedicated research facility in 2006. Homestake carved out more than 370 miles of underground shafts, drifts and ramps, and Sanford Lab currently maintains about 12 miles for science activities. The main level for science is the 4850 Level, which can be accessed through the Yates and Ross shafts. At 1,490 meters, SURF is the deepest underground laboratory in the U.S. For experiments on

1830-559: The Sanford Lab Homestake Visitor Center. SURF is located in the former Homestake Gold Mine and encompasses 223 acres on the surface and 7,700 acres underground. The surface property includes both the Yates Campus and the Ross Campus, named respectively for the Yates and Ross Shafts, which provide access to underground areas. The property was donated by Homestake's parent company, Barrick Gold, to

1891-496: The Sanford Underground Research Facility, Black Hills State University and the Sanford Lab Homestake Visitor Center. The SSEC is committed to developing and facilitating rich, innovative learning experiences and preparing the next generation of scientists, engineers, mathematicians and educators. The SSEC lends support to Sanford Lab's Education and Outreach programs, BHSU's Underground Campus and

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1952-649: The South Dakota Department of Environment and Natural Resources (DENR) for their “outstanding operation of the wastewater system and environmental compliance” with DENR's Surface Water Discharge Permit Award. The facility is housed at the previous Homestake Gold Mine, a deep underground gold mine founded during the Black Hills Gold Rush in 1876. In the late 1960s, the mine hosted the Homestake experiment . The operation, also known as

2013-430: The TPC but then exits, it will likely also deposit energy in the scintillator. These energy deposits are accompanied by emission of optical photons , which can be detected by an array of photomultiplier tubes (PMTs) located outside of the acrylic tanks. By observing such a signal in coincidence with a scatter in the TPC, it becomes possible to reject backgrounds in the TPC that might otherwise look like WIMP scatters. This

2074-640: The Universe and at what rate and how much energy is produced during the process. The construction of the accelerator begun around 2015 and achieved first beam in 2017. In spring of 2021, the CASPAR experiment was mothballed due to excavations starting nearby. The accelerator was disassembled and put into storage. The research group plans to return to SURF in the future. Majorana Demonstrator : The Majorana Demonstrator uses 40 kilograms of pure germanium crystals enclosed in deep-freeze cryostat modules to answer one of

2135-514: The Waste Water Treatment Plant (WWTP). To keep naturally-infiltrating water from accumulating underground, approximately 700 gallons of water per minute are pumped from underground to a surface reservoir where it awaits the treatment process. The water, pumped from the deepest drifts of the Sanford Lab and the tailing-laden reservoir of Grizzly Gulch, is filtered through multiple systems that clean dirt, minerals and toxins from

2196-548: The background-only hypothesis (no WIMP interactions) with a p-value of 0.35. This was the most sensitive dark matter direct detection result in the world, and ruled out low-mass WIMP signal hints such as from CoGeNT and CDMS-II . These results struck out some of the theories about WIMPs, allowing researchers to focus on fewer leads. In the final run from October 2014 to May 2016, at four times its original design sensitivity with 368 kg of liquid xenon, LUX saw no signs of dark matter candidate—WIMPs. According to Ethan Siegel ,

2257-554: The creation of Sanford Lab in 2007. After an extensive dewatering process, the 4850 Level of Sanford Lab was dedicated by South Dakota Governor Mike Rounds and T. Denny Sanford in 2009. The underground dedication took place in a space now designated as Governor's Corner. In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through

2318-406: The detector components composing the TPC and cryostats . Moreover, the relatively large density of liquid xenon allows the TPC to "self-shield" to a degree: gamma rays (neutrons) entering the TPC can travel only approximately a few centimeters (10 centimeters) before scattering and being stopped. As a result, the innermost volume of the detector is largely free of many of these backgrounds. Because it

2379-560: The electric field). The x-y coordinate of the event was inferred from electroluminescence photons at the top array by statistical methods ( Monte Carlo and maximum likelihood estimation ) to a resolution under 1 cm. WIMPs would be expected to interact exclusively with the liquid xenon nuclei, resulting in nuclear recoils that would appear very similar to neutron collisions. In order to single out WIMP interactions, neutron events must be minimized, through shielding and ultra-quiet building materials. In order to discern WIMPs from neutrons,

2440-400: The environment, interactions from neutrons produced in the environment, and interactions from cosmic ray muons produced in the upper atmosphere. The two goals of a dark matter search are to minimize the number of these background interactions, and for those that do occur, to be able to identify that they are from background (as opposed to WIMPs). First, the innermost detector is composed of

2501-583: The facility are not available, in 2015, Sanford Lab built the Sanford Lab Homestake Visitor Center . Overlooking the ridge of the 1,000-foot-deep Open Cut, the visitor center promotes public appreciation of Lead's rich mining history and an understanding of the science advancing at Sanford Lab. Formalized in the spring of 2014, the Sanford Science Education Center (SSEC) is a partnership between

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2562-488: The facility as a possible future site for the United States’ Deep Underground Science and Engineering Laboratory (DUSEL). In 2006, the facility's namesake T. Denny Sanford donated $ 70 million to the facility, Barrick Gold Corporation made a land donation and state legislation formed the South Dakota Science and Technology Authority (SDSTA), a quasi-government entity. These developments culminated with

2623-409: The flow of heated water. Boreholes at the 4100 level monitor water injection and recovery using electrical impedance tomography and seismic signal analysis. GEOXTM: GEOXTM hopes to create the world's largest, deepest network of underground fiber-optic strain and temperature sensors and tiltmeters to measure the movement of rock systems in the underground laboratory. Transparent Earth: The project

2684-429: The gas at the surface by a stronger electric field, and produced electroluminescence photons detected as the S2 signal. The S1 and subsequent S2 signal constituted a particle interaction in the liquid xenon. The detector was a time-projection chamber (TPC), using the time between S1 and S2 signals to find the interaction depth since electrons move at constant velocity in liquid xenon (around 1–2 km/s, depending on

2745-434: The life of an experiment. A consortium agreement between LBC owners allows the counters to be available to other universities and partners, creating opportunities for collaborative research. While the counters are dedicated to supporting high-priority experiments, the consortium allows those counters to also be used for all collaborations and academic users when there is space to spare. The Surface Assembly Laboratory (SAL)

2806-470: The liquid surface, are pulled into the gas and create electroluminescence light in a stronger electric field. This electroluminescence creates a delayed "S2" signal. The externally-created electric fields are created by a set of four high voltage electrode grids: the bottom, the cathode, the gate, and the anode. Taken together, the S1 and S2 enable precise 3D reconstruction of the position of an interaction in

2867-587: The majority of the US component of the ZEPLIN II experiment, and groups involved in low-background rare event searches such as Super Kamiokande , SNO , IceCube , Kamland , EXO and Double Chooz . The LUX experiment's co-spokesmen were Richard Gaitskell from Brown University (who acted as co-spokesman from 2007 on) and Daniel McKinsey from University of California, Berkeley (who acted as co-spokesman from 2012 on). Tom Shutt from Case Western Reserve University

2928-514: The most challenging and important questions in physics: are neutrinos their own antiparticles? If the answer is yes, it will require rewriting the Standard Model of Particles and Interactions, our basic understanding of the physical world. CUSSP: Center for Understanding Subsurface Signals and Permeability seeks to improve energy recovery from geothermal sites by better understanding how to induce fractures in geothermal reservoirs and direct

2989-439: The number of single interactions must be compared to multiple events. Since WIMPs are expected to be so weakly interacting, most would pass through the detector unnoticed. Any WIMPs that interact will have negligible chance of repeated interaction. Neutrons, on the other hand, have a reasonably large chance of multiple collisions within the target volume, the frequency of which can be accurately predicted. Using this knowledge, if

3050-516: The ratio of single interactions to multiple interactions exceeds a certain value, the detection of dark matter may be reliably inferred. The LUX collaboration was composed of over 100 scientists and engineers across 27 institutions in the US and Europe. LUX was composed of the majority of the US groups that collaborated in the XENON10 experiment, most of the groups in the ZEPLIN III experiment,

3111-402: The results from LUX and XENON1T have provided evidence against the supersymmetric "WIMP Miracle" strong enough to motivate theorists towards alternate models of dark matter. 44°21′07″N 103°45′04″W  /  44.352°N 103.751°W  / 44.352; -103.751 Sanford Underground Laboratory The Sanford Underground Research Facility (SURF) , or Sanford Lab ,

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3172-473: The water, making it safe to return to natural stream systems. Once treated, the water is released into Gold Run Creek , which joins Whitewood Creek within a few hundred yards of the discharge pipe. Sanford Lab monitors the health of these streams, counting fish and macro invertebrate populations and tests for contaminants. For this regulation, in 2019, the WWTP was recognized for the eleventh consecutive year by

3233-424: The xenon atom to ricochet around the area near the site of the scatter, converting its energy into the production of prompt scintillation photons, freed (ionization) electrons, and heat. A number of the prompt scintillation photons can be detected by the photomultiplier tubes (PMTs) at the top and bottom of the detector. The ionization electrons drift upward in an externally applied electric field , and upon reaching

3294-402: The xenon in the liquid phase (approximately 178K). This inner cryostat is nested in a larger, outer cryostat, which helps limit heat transfer into the xenon. External to the outer cryostat is a set of acrylic tanks holding liquid scintillator . This scintillator is liquid-alkyl-benzene (LAB) loaded with gadolinium for more efficient neutron capture. If a gamma ray or neutron scatters once inside

3355-401: The xenon. Interactions in liquid xenon generate 175 nm ultraviolet photons and electrons. These photons were immediately detected by two arrays of 61 photomultiplier tubes at the top and bottom of the detector. These prompt photons were the S1 signal. Electrons generated by the particle interactions drifted upwards towards the xenon gas by an electric field. The electrons were pulled in

3416-527: The xenon. Because the S2 happens very close to the upper PMT array, it alone can give a good sense of where in XY (i.e. relative to the detector axis) the interaction has occurred. The time difference between the prompt S1 and delayed S2 is a proxy for the depth of the interaction: by using the drift velocity of electrons in xenon at a given electric field, one can convert the drift time to a physical depth, or Z position. Together, this XYZ position permits one to identify

3477-429: Was LUX co-spokesman between 2007 and 2012. Detector assembly began in late 2009. The LUX detector was commissioned overground at SURF for a six-month run. The assembled detector was transported underground from the surface laboratory in a two-day operation in the summer of 2012 and began data taking April 2013, presenting initial results Fall 2013. It was decommissioned in 2016. The next-generation follow-up experiment,

3538-412: Was a precursor to EGS Collab. EGS Collab : The Enhanced Geothermal Systems (EGS) Collab Project is a collaboration of eight national laboratories and six universities who are working to improve geothermal technologies. EGS conducts field experiments to better understand and model rock fracturing and other elements of geothermal energy. The experiment was a precursor to CUSSP. DUGL: For several years,

3599-467: Was excavated for Ray Davis's experiment in the 1960s. In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive dark matter detector in the world. The Majorana experiment is searching for a rare type of radioactive decay called “neutrinoless double-beta decay.” If this phenomenon were detected, it could confirm that neutrinos are their own antiparticles and provide clues as to why matter prevailed over antimatter. In 2017,

3660-454: Was operated underground to reduce the background noise signal caused by high-energy cosmic rays at the Earth's surface. The detector was decommissioned in 2016 and is now on display at the Sanford Lab Homestake Visitor Center . The detector was isolated from background particles by a surrounding water tank and the earth above. This shielding reduced cosmic rays and radiation interacting with

3721-567: Was redesigned and enlarged for dark matter experiments. The first, the Large Underground Xenon experiment (LUX), operated from 2013 to 2016. The Davis Cavern gave the experiment the environment it needed to become the most sensitive dark matter detector in the world, a spot it held for more than one year after it was decommissioned. This state-of-the-art laboratory features a 72,000-gallon (272,549 liters) water tank, which serves as additional shielding from cosmic radiation; and

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