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The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory ( SNO ) results have provided revolutionary insight into the properties of neutrinos and the core of the sun. The detector, shown in the artist's conception below, was built 6800 feet under ground, in VALE's Creighton mine near Sudbury, Ontario, Canada. SNO was a heavy-water Cherenkov detector designed to detect neutrinos produced by fusion reactions in the sun. It used 1000 tonnes of heavy water loaned from Atomic Energy of Canada Limited (AECL), and contained by a 12 meter diameter acrylic vessel. Neutrinos reacted with the heavy water (D 2 O) to produce flashes of light called Cherenkov radiation. This light was then detected by an array of 9600 photomultiplier tubes mounted on a geodesic support structure surrounding the heavy water vessel. The detector was immersed in light (normal) water within a 30 meter barrel-shaped cavity (the size of a 10 story building!) excavated from Norite rock. Located in the deepest part of the mine, the overburden of rock shielded the detector from cosmic rays. The detector laboratory, still functioning as part of the new SNOLAB facility, is extremely clean to reduce background signals from radioactive elements present in the mine dust which would otherwise hide the very weak signal from neutrinos. Plans are currently underway to upgrade the SNO detector for the new SNO+ experiment.

The first co-spokesmen for the SNO collaboration when it was established in 1984 were Professor Herb Chen from U California, Irvine and Professor George Ewan, Queen’s University. For interesting accounts of the early development work for the SNO experiment, please see: " Early Development of the Underground SNO Laboratory in Canada " and " The Funding Campaign for the Sudbury Neutrino Observatory ", G.T. Ewan and W.F. Davidson, Physics in Canada, Vol. 61, No. 6 (2005), p. 339-346 and 347-350. ( download in PDF format )

For a review article summarizing the three phases of the SNO experiment, please see: " The Sudbury Neutrino Observatory ", Nick Jelley, Arthur B. McDonald, and R.G. Hamish Robertson, Annu. Rev. Nucl. Part. Sci. 2009.59:431-465. ( download in PDF format )

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• Published: 09 June 2021

Neutrino physics over the two decades since the first SNO result

• Arthur B. McDonald 1  

Nature Reviews Physics volume  3 ,  pages 456–457 ( 2021 ) Cite this article

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Writing on behalf of the Sudbury Neutrino Observatory (SNO) collaboration, Arthur McDonald recalls the discoveries that followed the SNO result on solar neutrino fluxes, published 20 years ago.

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Jelley, N. et al. The Sudbury Neutrino Observatory. Annu. Rev. Nucl. Part. Sci. 59 , 431–465 (2009).

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Aharmim, B. et al. Cosmogenic neutron production at the Sudbury Neutrino Observatory. Phys. Rev. D 100 , 112005 (2019).

Aharmim, B. et al. Search for hep solar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory. Phys. Rev. D 102 , 062006 (2020).

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Ahn, J. K. et al. Observation of reactor electron antineutrinos disappearance in the RENO Experiment. Phys. Rev. Lett. 108 , 191802 (2012).

Aker, M. et al. Improved upper limit on the neutrino mass from a direct kinematic method by KATRIN. Phys. Rev. Lett. 123 , 221802 (2019).

The Borexino Collaboration. Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun. Nature 587 , 577–582 (2020).

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McDonald, A.B. Neutrino physics over the two decades since the first SNO result. Nat Rev Phys 3 , 456–457 (2021). https://doi.org/10.1038/s42254-021-00339-w

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It may be snowy outside, but the water in the SNO+ experiment isn’t for building snowmen. SNO+ is short for the Sudbury Neutrino Observation+, a  neutrino experiment 2 kilometers underground in a mine in Ontario, Canada. It’s supported by the Department of Energy’s Office of Science and several DOE national laboratories. Scientists are using SNO+ to study everything from big questions of the universe to  developing tools for nuclear non-proliferation .  

Neutrinos are tiny, mysterious particles that hardly interact with anything. But they’re a major player in physics. In addition to being one of the fundamental particles described in the Standard Model of Particle Physics, they may hold the key to some of the field’s biggest questions.

One of those questions is “Why is there so much more matter than antimatter?” According to the laws of physics as we know them, there should have been the same amount of matter and antimatter at the start of the universe. But if that was true, they would have destroyed each other and we wouldn’t be here. Obviously, something is missing. 

One theory about the neutrino could provide a possible explanation. All of the fundamental particles in the Standard Model of Particle Physics have their own antimatter partner. This partner is a very similar particle with the same mass, same amount of electric charge, and same magnetic moment as the familiar ordinary matter one. However, the antimatter particles have an opposite sign of electric charge and magnetic moment. For example, the antimatter particle of the electron is the positron. It has a positive charge instead of a negative one. 

This is where it gets really weird. Scientists think the neutrino may be its own antimatter partner. An Italian physicist named Ettore Majorana theorized almost 100 years ago that such a particle exists – called a Majorana fermion. But no one has ever observed this phenomenon in an experiment. A specific process called neutrinoless double beta decay could provide this missing evidence. In addition to answering the matter-antimatter question, it could also explain why the neutrino has mass at all. The current Standard Model of Particle Physics predicts that it shouldn’t. And yet experiments show that it does. If the neutrinoless double beta decay exists, the SNO+ experiment is designed to detect it. 

Scientists are also using SNO+ to study a number of other questions related to neutrinos. In addition to their implications for particle physics, neutrinos can also be used to study nuclear power plants. Nuclear reactors produce trillions of antineutrinos every second. (Antineutrinos are partners of regular neutrinos, but not antimatter versions. Scientists use and measure them in very similar ways.) The amount of heat a nuclear reactor produces determines how many antineutrinos it produces. Similarly, the type of fuel the reactor burns determines the energy spectrum of those antineutrinos. In theory, by measuring antineutrinos coming off of a nuclear reactor, scientists should be able to tell the type of fuel a reactor is burning and how it functions. In the future, it could be possible to use neutrino detectors to see if a country has switched from using a nuclear reactor to produce electricity to developing nuclear weapons. They could be a valuable tool for enforcing nuclear weapons treaties and supporting nuclear non-proliferation.

To study neutrinos, SNO+ uses a 12-meter acrylic sphere. It’s filled with 780 tons of a specific liquid that gives off light when charged particles move through it. (On the rare occasion neutrinos interact with electrons or nuclei, they produce charged particles.) The sphere is suspended in an even bigger sphere filled with 7,000 tonnes of ultrapure water. This bigger sphere also contains 10,000 specialized tubes that detect flashes of light.

Before SNO+ officially launched, scientists took advantage of an unusual situation. SNO+ is an upgrade of the original SNO experiment. As scientists were in the process of upgrading it in 2018, they filled the smaller sphere with ultrapure water. They did this to calibrate certain components and measure background signals. Knowing that the sphere wouldn’t be filled with water in the future, the SNO+ Collaboration took measurements that they wouldn’t be able to do later on.

In particular, they wanted to test how well the SNO+ experiment filled with water could detect antineutrinos from nuclear reactors. SNO+ is conveniently located near three nuclear power plants, with the closest one a little less than 100 miles away. The main sphere being filled with water presented a unique opportunity. To detect neutrinos, detectors use huge amounts of liquid. Most neutrino detectors (including the final version of SNO+) use a non-water liquid. Using water in detectors to monitor nuclear reactions would be much more affordable. With that set-up, the scientists demonstrated that they could accurately  detect antineutrinos with a detector that used only pure water . That’s a step forward for developing neutrino detectors specifically for nuclear non-proliferation. 

From solving the deep mysteries of the universe to helping keep people on Earth safe, neutrino experiments are shining light on this strange particle. 

SNOLAB is located on the traditional territory of the Robinson-Huron Treaty of 1850, shared by the Indigenous people of the surrounding Atikameksheng Anishnawbek First Nation as part of the larger Anishinabek Nation.

We acknowledge those who came before us and honour those who are the caretakers of this land and the waters.

SNOLAB is Canada’s deep underground research laboratory, located in Vale’s Creighton mine near Sudbury, Ontario Canada.

It provides an ideal low background environment for the study of extremely rare physical interactions. SNOLAB’s science program focuses on astroparticle physics, specifically neutrino and dark matter studies, though its unique location is also well-suited to biology and geology experiments. SNOLAB facilitates world-class research, trains highly qualified personnel, and inspires the next generation of scientists.

At 2km, SNOLAB is the deepest cleanest lab in the world. It is an expansion of the facilities constructed for the Sudbury Neutrino Observatory (SNO) solar neutrino experiment and has 5,000 m 2 of clean space underground for experiments and supporting infrastructure. A staff of over 100 support the science, providing business processes, engineering design, construction, installation, technical support, and operations. SNOLAB research scientists provide expert and local support to the experiments and undertake research in their own right as members of experimental collaborations.

History of SNOLAB

From 1970 to 1994, there was another underground neutrino detector set up in a mine in South Dakota. The Homestake experiment, a brainchild of Dr. Ray Davis, was set up to measure neutrinos from the Sun. The data collected presented a problem: the detector measured only about a third the number of neutrinos predicted by theorists. The experiment appeared to be sound, so what was going on? Physicists were concerned there may be fundamental flaws in the Standard Model, something wrong with our entire understanding of physics. There was even a possibility the diminished neutrino output was a sign that the Sun was actually going out (because of electromagnetic interactions light takes much longer to escape the Sun than neutrinos, so this was a valid concern).

The SNO experiment was designed to address this question, dubbed by physicists ‘The Solar Neutrino Problem’. Scientists knew that neutrinos came in three flavours: electron, muon, and tau. Up until this point, it was assumed that they did not change flavour. The Homestake experiment was sensitive only to electron neutrinos, the flavour produced in the Sun. SNO was designed to be sensitive to all three flavours of neutrino. Years of data from the SNO experiment found that in fact the Sun was creating the expected number of neutrinos, but they were changing flavour on their journey to Earth, so the Homestake experiment missed some of them. This finding was corroborated by the Super-Kamiokande detector in Japan, and the 2015 Nobel Prize in physics was awarded to Dr. Art McDonald of SNO and Dr. Takaki Kajita of Super-K.

The success of SNO and a strong working relationship with Inco (later Vale) meant plans to expand the lab were already in the works as SNO was still collecting data. The SNOLAB expansion added an additional 6,300 m 2 of excavations, of which 3,700 m 2 is clean room space, attached to the existing facility. The clean/dirty boundary was moved for the expanded laboratory and some existing excavations were converted to additional clean space. SNOLAB construction took place in two phases. Phase I added a new laboratory entrance and service facilities (chiller, generator, wastewater treatment), and new experimental areas: a network of drifts (Ladder Labs) for small and medium sized experiments and a large experimental hall (the Cube Hall) for a bigger experiment. Phase II consisted of an additional larger experimental space dubbed the Cryopit which is designed for an experiment using a large volume of cryogenic liquid and is isolated from the rest of the laboratory for safety in the event of a cryogen leak. In addition to the new laboratory space, there is also the existing SNO cavern and its associated Utility Drift and control room.

SNOLAB was constructed using capital funds totalling $70M, including an initial $38.9M capital award from the Canada Foundation for Innovation through the International Joint Venture program. The Ontario Innovation Trust, the Northern Ontario Heritage Fund, and FedNor provided additional funds enabling construction.

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The SNO+ Experiment

"A detector that works perfectly at all times would be considered either obsolete or not daring enough in conception." - Sharon Traweek

Cosmic rays, or the millions of high-energy particles bombarding each square meter of the planet every second, mimic the signals of neutrinos and 'drown out' the detector, making neutrino detection impossible. However, this cosmic ray 'background' can be removed by putting a lot of 'stuff' that can absorb cosmic rays between the detector and space. In the case of SNO+, the 'stuff' we use is 2km of Canadian Shield. The SNO+ detector is situated underground at the SNOLAB research facility. Originally built to house the SNO experiment, SNOLAB has since expanded to be one of the deepest and cleanest underground research facilities in the world, housing several world-class neutrino and dark matter experiments.

SNOLAB is located near Sudbury (Ontario) in Creighton Mine, an active nickel and copper mine run by the Vale mining corporation.

The SNO+ Detector

The main detector is a 6m radius acrylic vessel (AV), is filled with 780 tonnes of linear alkylbenzene, our liquid scintillator following a major upgrade . Neutrino interactions within the AV are viewed by ~9300 photomultiplier tubes (PMTs), which are mounted on a steel PMT SUPport structure (PSUP) outside of the AV. This steel structure is located in a ~20m tall cavity dug into the rock 2km underground at SNOLAB (in the Creighton Mine). The cavity is filled with ultra-pure water to reduce undesirable background events from trace amounts of uranium and thorium in the surrounding rock.

The SNO+ Physics Programme

Neutrinoless double beta decay.

Solar Neutrinos

The usage of liquid scintillator will allow for a lower energy threshold in SNO+ than in the original Sudbury Neutrino Observatory. SNO+ will be sensitive to pep and CNO neutrinos produced in the Sun. The production rate of pep neutrinos in the Sun is extremely well known, so a measurement of the pep neutrino flux at the Earth will show the "survival probability" of the original neutrino flavour and test neutrino oscillation models. Meanwhile, a measurement of the CNO flux will give insight into the "solar metallicity problem", an unresolved issue regarding the metal content in the core of the Sun.

Antineutrinos

SNO+ is able to detect antineutrinos through an inverse beta decay interaction that can occur in the liquid scintillator. Antineutrinos are created from radioactive materials in the crust and mantle of the Earth (geoneutrinos), as well as in nuclear reactors. A measurement of geoneutrinos will give insight into two properties of the Earth that are not well understood: the heating mechanism of the Earth, and test models of the bulk composition of the Earth's mantle and crust. Near SNO+ are nuclear power plants in Ontario. As the neutrino production from nuclear reactors and their distances from SNO+ are very well known, this will allow for extremely precise neutrino oscillation measurements.

Supernova Neutrinos

When the outward pressure due to fusion reactions in the core of a dying star is not enough to overcome the force of gravity from the outer envelope of the star, the envelope comes crashing into the core in what is known as a supernova.  Over 99% of the energy of a supernova is released in the form of neutrinos. Furthermore, while the photons from the explosion are jumbled in the collapsing envelope, the neutrinos are expelled mostly unphased. Therefore, the neutrinos are not only the most representative signal of a supernova, but can act as a warning to astronomers of an imminent supernova. SNO+ will be a member of the Supernova Early Warning System (SNEWS), which is a collaborative effort between 8 neutrino experiments to detect supernovae in advance of their light signals.

Exotic Physics Searches

The extremely low-background conditions, high sensitivity, and low energy threshold of the SNO+ experiment allows for the detection capabilities of other Beyond-Standard-Model physics. This includes the search for invisible nucleon decay (decays of nucleons into modes where daughter products deposit no energy in the detector), and axion-like particles (hypothetical particles that can solve issues such as the Strong CP problem).

SNO Experiment

The Sudbury Neutrino Observatory (SNO) was built as a water Cherenkov detector dedicated to investigate elementary particles called neutrinos. It was built  2070 m below the surface in shaft number 9 of the INCO Creighton Nickel Mine near Sudbury, Ontario.

Prior to the SNO project, all of the solar neutrino experiments conducted had detected only a fraction of the number of expected neutrinos from the sun. This is called the Solar Neutrino Problem.

It was thought that If the previous experiments were correct, then either the general understanding of the sun is seriously wrong, or 'neutrino oscillations' (which imply a non-zero neutrino mass) are reducing the number of detected electron neutrinos.

SNO was designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector was unique in its use of heavy water as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates.

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Nobel Prize—Neutrinos Oscillate

The 2015 Nobel Prize in physics recognizes the discovery that neutrinos transform or “oscillate” among three different types. In a single stroke, it both solved a long-standing puzzle about these most elusive of fundamental particles and also exposed an incompleteness in the current bedrock theory of physics, called the standard model. The key findings behind the award were reported in three papers published in Physical Review Letters between 1998 and 2002.

Neutrinos are extremely hard to detect because they have very little mass, no electric charge, and only weak interactions with other fundamental particles. Yet they are, after photons, the second most abundant known particle in the Universe and are essential for understanding the nuclear reactions involved in fusion, which powers stars, and in radioactive beta decay.

Although it was not clear, even after they were first detected in 1956, whether neutrinos have any mass, the standard model, which describes all of the particles currently known, assumes that they do not. It also says that there are three types (“flavors”) of neutrino, called electron, muon, and tau neutrinos. Neutrinos produced in solar nuclear fusion were first detected in the late 1960s, and over the ensuing three decades, such measurements showed that there was a deficit of about 70% compared with the number of neutrinos predicted from calculations.

This shortfall of solar neutrinos was explained by experiments led by this year's laureates, Arthur McDonald of Queen’s University in Kingston, Canada, and Takaaki Kajita of the University of Tokyo. The work revealed that the three flavors of neutrino can interconvert as the particles stream through space. Thus, some electron neutrinos produced in the Sun become muon and tau neutrinos in transit—but the earlier detectors were not sensitive to these latter two flavors. The possibility of neutrino oscillations was first raised in 1957, but the Nobel-winning work demonstrated that such oscillations really do occur.

Kajita headed a team working at the Super-Kamiokande detector in Japan. The detector consists of a tank of 50,000 tons of water buried underground to shield it from cosmic rays. It detects electron and muon neutrinos coming not from the Sun but from the Earth’s atmosphere, where neutrinos are produced by collisions of cosmic rays with atmospheric atoms. Very rarely, these neutrinos will collide with atomic nuclei in the detector's water molecules and generate flashes of light.

Neutrinos interact so weakly with matter that they mostly pass straight through the Earth without disturbance, so Super-Kamiokande can detect neutrinos coming from any direction. In 1998, the researchers reported that they detected fewer muon neutrinos coming up through the Earth than coming down from above. This asymmetry suggested that some atmospheric muon neutrinos coming through the Earth had oscillated to (undetectable) tau neutrinos in transit, while those coming from above, having a far shorter path, had not had time to do so.

The experiment led by McDonald confirmed this conclusion in 2001 and 2002. It used a detector called the Sudbury Neutrino Observatory (SNO) inside a mine in Sudbury, Canada, containing 1000 tons of heavy water. In this case there were two types of collisions between neutrinos and heavy hydrogen (deuterium) atoms, one involving only electron neutrinos and the other involving all three flavors. So the relative amounts of the different flavors could be compared.

“The resolution of the solar neutrino flux was the major result,” says Frank Close, a particle physicist at the University of Oxford. “It was a problem that hung around for about 40 years.” He adds that SNO “would not exist in the way it does but for the persistence and energy of Art McDonald.”

In addition to explaining the solar neutrino deficit, these discoveries implied that neutrinos are not massless—according to theory, oscillations are only possible if there are differences in mass between the three flavors. It’s not yet known what these masses are, but they are very small, at least a million times less than the electron mass. And yet neutrinos are so numerous that they add up to a mass roughly equivalent to that of all the luminous matter in the Universe. Moreover, because the standard model is predicated on massless neutrinos, new theories will be required to explain why they have mass, so the discoveries of McDonald, Kajita, and their teams, point to future directions in physics research. Close says there are several current urgent questions regarding neutrinos, such as their potential connections with the mysterious dark matter and with the puzzling asymmetry between matter and antimatter.

–Philip Ball

Philip Ball is a freelance science writer in London. His latest book is How Life Works  (Picador, 2024).

More Information

Neutrinos Have Mass — Focus story on the 1998 paper by Kajita and colleagues

Evidence for Oscillation of Atmospheric Neutrinos

Y. Fukuda et al. (Super-Kamiokande Collaboration)

Phys. Rev. Lett. 81 , 1562 (1998)

Published August 24, 1998

Measurement of the Rate of ν e + d → p + p + e − Interactions Produced by B 8 Solar Neutrinos at the Sudbury Neutrino Observatory

Q. R. Ahmad et al. (SNO Collaboration)

Phys. Rev. Lett. 87 , 071301 (2001)

Published July 25, 2001

Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory

Phys. Rev. Lett. 89 , 011301 (2002)

Published June 13, 2002

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Historic Sudbury Neutrino Observatory Data, Carried by ESnet, Lives on at NERSC

January 26, 2010

Contact: Linda Vu, lvu@lbl.gov , +1 510 486 2402

SNO onsists of an 18-meters-in-diameter stainless steel geodesic sphere inside of which is an acrylic vessel filled with 1000 tons of heavy water (deuterium oxide or D2O). Attached to the sphere are 9,522 ultra-sensitive light-sensors called photomultiplier tubes. When neutrinos passing through the heavy water interact with deuterium nuclei, flashes of light are emitted. The photomultiplier tubes detect these light flashes and convert them into electronic signals that scientists can analyze for the presence of all three types of neutrinos. (Credit: Photo by Roy Kaltschmidt)

Tunneled 6,800 feet underground in Canada's Vale Inco Creighton mine, the Sudbury Neutrino Observatory (SNO) was designed to detect neutrinos produced by fusion reactions in the Sun. Although the observatory officially "switched off" in August 2006, a copy of all the data generated for and by the experiment will live on at the National Energy Research Scientific Computing Center (NERSC).

"NERSC has been providing great support to SNO for over a decade. We used the PDSF cluster do some of the early analyses and were really appreciative of the support that we received from NERSC staff. When we looked around at different facilities and talked to colleagues that have used the center's High Performance Storage System [HPSS] extensively, we immediately concluded that one copy of our data should be stored at NERSC," says Alan Poon, a member of the SNO collaboration at the Lawrence Berkeley National Laboratory (Berkeley Lab).

"The Department of Energy invested a lot of resources into SNO, and we believe that preserving these datasets at NERSC will afford the best protection of the agency's investment," he adds.

According to Poon, the SNO experiment has made tremendous contributions to humanity's understanding of neutrinos, invisible elementary particles that permeate the cosmos. Before the observatory started searching for solar neutrinos on Earth, all experiments up to that point detected only a fraction of the particles predicted to exist by detailed theories of energy production in the Sun. Results from the SNO experiment eventually revealed that the total number of neutrinos produced in the Sun is just as predicted by solar models, but the neutrinos are oscillating in transit, changing in type or "flavor" from electron neutrinos (the flavor produced in the Sun) to muon or tau neutrinos. In 2001, Science Magazine identified SNO’s solution to the solar neutrino mystery as one of their 10 science breakthroughs of the year.

"SNO data will be unique for decades to come. There will not be another experiment in the foreseeable future that would provide the same measurement with better precision and accuracy," says Ryan Martin, a postdoctoral researcher at the Berkeley Lab who helped migrate data from disks at the SNO facility in Sudbury, Canada, to the NERSC facility in Oakland, Calif. "It is important to preserve this data for the scientific community, in case a new theory would require further studies of the data."

Martin worked closely with Damian Hazen of NERSC's Storage Systems Group to transfer 26 terabytes of data across the DOE's Energy Sciences Network (ESnet) to NERSC's HPSS. This set includes everything from the raw data generated by the experiment and processed data used during analysis to the computer codes and simulations used for detector design and scientific computation.

"From testing the transfer speed, tuning the network and identifying packet losses, to the final archiving at HPSS, the center's expertise saved us a lot of headache," says Martin. "These are technical issues that laymen like us would take a long time to solve, if at all. We have been really pleased with the help that NERSC staff have provided."

For more information about SNO, please visit: http://newscenter.lbl.gov/feature-stories/2003/09/23/a-dash-of-salt-enhances-sno-results/

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SNO+ experiment makes astroparticle physics history

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The experiment is still ongoing, but SNO+ at Sudbury’s SNOLAB has achieved a breakthrough by becoming the first detector on the planet to detect antineutrinos using only ultrapure water and from hundreds of kilometres away.

The finding, SNOLAB said in a news release, could assist in monitoring nuclear power stations around the world.

“While filled with ultrapure water as the detector’s components were being upgraded in  2018, 190 days of data yielded results that surprised the experiment team and is a first in  the field of astroparticle physics,” SNOLAB said.

Among the data collected “was an antineutrino signal that came from the Bruce, Darlington and Pickering nuclear generating stations hundreds of kilometres away.”

As explained by SNOLAB, antineutrinos are a byproduct of nuclear fission when a neutron decays into a proton and an electron in reactors. The scientists didn’t expect they would be able to see antineutrinos in ultrapure water, so the result suggests it is possible to use neutrino detectors such as SNO+ to monitor a reactor’s power production continuously and from a great distance. 

What was also surprising, SNOLAB said, was that the antineutrino signal was detected in “non-toxic, inexpensive and easy-to-handle” ultrapure water.

“It intrigues us that pure water can be used to measure antineutrinos from reactors and at  such large distances,” said SNO+ collaboration member Logan Lebanowski. “We spent significant effort to extract a handful of signals from 190 days of data. The result is gratifying.”

The SNO+ experiment, SNOLAB said, is an upgrade to the Sudbury Neutrino Observatory  (SNO) experiment. 

The five-storey tall experiment vessel is currently filled with a liquid scintillator (much like a mineral oil) that produces light when charged particles pass through it.

“This finding is a great indicator that we can expect very exciting physics from the scintillator phase, running now for nearly 10 months, well into the future,” said SNOLAB research scientist Christine Kraus. 

SNO+ is searching for the as yet undetected nuclear-decay process. If the decay is spotted, researchers could confirm that a neutrino is its own antiparticle.

A paper detailing the SNO+ findings, “Evidence of Antineutrinos from Distant Reactors using  Pure Water at SNO+” will be published by the American Physical Society ’s Physics Magazine on March 9. Read a synopsis of the paper here . 

SNOLAB is located two kilometres underground at Creighton Mine in Greater Sudbury. It is the site of the Nobel Prize-winning Sudbury Neutrino Observatory.

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Neutrino Physics

Neutrino oscillation.

Neutrino oscillations arise from a quantum mechanical phenomenon associated with the fact that the neutrinos have mass. For the three neutrinos species that we know to exist, the principle of superposition allows "flavor" states, namely neutrinos that interact to produce electrons, muons, or taus, to be (orthogonal) combinations of three neutrino states with definite mass. In other words, when a weak interaction produces a flavor state, such as a muon neutrino, that state is a mixture of states with different mass. These states evolve at different rates so that a later time, the state may acquire some component of a new flavor state, such that if it interacts, it may do so as a flavor state different from its original flavor. This possibility of flavor change, namely that a neutrino is created in one flavor and interacts some time later as another, is the primary manifestation of neutrino oscillations.

Big Questions

The observation of neutrino oscillations in 1998 by the Super-Kamiokande experiment, established that neutrinos have non-zero and  non-degenerate masses. Around the same time, the SNO experiment definitively showed that electron neutrinos born in the core of the sun, transition to a mixture of all three flavors, explaining the fewer-than-expected number of electron neutrinos detected on Earth. These developments shared the 2015 Nobel Prize in Physics " for the discovery of neutrino oscillations, which shows that neutrinos have mass . These discoveries and subsequent developments have opened a vast new program of research which seeks to answer questions regarding neutrino flavor and masses and their role in the universe. These include:

• Do neutrinos and antineutrinos oscillate in the same way? Or do they exhibit "CP violation", an asymmetry between matter and antimatter?
• Is there a pattern in the fundamental parameters which relate the neutrino flavor and mass states that point to new symmetries or physics?
• What is the pattern of neutrino masses and why are they so small, more than a million times smaller than the electron, the next lighest particle? Do they get masses from a different source than other particles (e.g. the Higgs mechanism)?
• Are there additional species of neutrnos than those we know about? Do they have exotic properties that can't be explained by the Standard Model?

What role do neutrinos have in the evolution of the Universe? Are they the reason for why the universe is matter dominated?

Detecting Neutrinos

BIG detector : One of the defining properties of neutrinos is their extremely feeble interaction with other particles. While increasingly powerful accelerators with proton beams approaching 1 megawatt of power are being used to produce neutrinos,  enormous detectors with tons (for near/short base line detectors ~100 m away from the source) or kilotons (for far detectors ~1000 km from the source) of mass are needed in order to obtain enough observations of neutrino interactions to make precise measurments of neuttrino properties, including neutrino oscillations.

Neutrino-Nuclear Cross-sections : In order to make enormous neutrino detectors, we have turned to cheap and abundant materials that nonetheless allow us to observe neutrino interactions by detecting the particles which come out of them. To this end, we need to accurately understand how a neutrino interacts with the nuclei in the detector material (e.g. hydrogen and oxygen in the case of water, argon in the case of a liquid argon time projection chamber). The strongly coupled dynamics inside the nucleus have made detailed and precise predictions extraordinarily difficult, particularly in the GeV energy region where pions and other particles can be produced through the excitation of hadronic resonances.  Detailed and precise measurements of neutrino-nucleus interactions are essential to infer physics of neutrinos such as neutrino oscillations.

Experimental Programs at SLAC

At SLAC, we are invovled with several experiments that are at the forefront of the worldwide program to understand neutrino oscillations:

• MicroBooNE and ICARUS:  These two experiments at Fermilab search for neutrinos oscillations that may be associated with heavier exotic neutrinos that oscillate "faster" than those that arise from the three neutrinos we know of. They are called "short baseline" experiments, and look for neutrinos to oscillate at a distance of ~1 km with a ~1 GeV muon neutrino beam. MicroBooNE has been operation for several years, while the much larger ICARUS detector is now being comissioned.
• T2K:  In this experiment, a neutrino beam from J-PARC, an accelerator facility on the east coast of Japan, is sent 295 km to the Super-Kamiokande detector. This distance is necessary for the "standard" neutrinos at an energy of ~600 MeV to exhibit their maximum neutrino oscillation effects.  This experiment first observed muon neutrino to electron neutrino oscillations, setting the groundwork for ongoing and future searches for CP violation in the form of an imbalance in the oscillation probabilities between this mode of neutrino oscillations and its antimatter counterpart.
• DUNE:  A future "long baseline" neutrino oscillation experiment where a new neutrino beam at Fermilab will send a muon (anti)neutrino beam to a set of large (~17 kt) detectors at the Sanford Underground Research Facility 1300 km away more than 1 km (1 mile) underground. The intense neutrino beam will allow precision measurements to definitely observe CP violation and observe additional effects from neutrino traveling through the Earth's crust that will provide important information on the neutrino mass pattern.
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After decade, SNOLAB now 'best location in world for future generation experiments'

Underground lab celebrating 10 years of offering clean space for multi-disciplinary research.

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Over the past decade, SNOLAB in Greater Sudbury, Ont., has built a reputation among scientists around the globe.

The lab space located 2 km underground means it's ideal for research that needs to be conducted away from the cosmic rays found on the surface. 

There's enough cleanspace for about a dozen multi-disciplinary experiments.

"It's unlike any other underground experience you've ever had," said Clarence Virtue, the interim executive director.

"All over the place, there are these experiments looking for dark matter or looking for neutrinoless double beta decay or looking for supernovae."

• Machine used to detect dark matter to be tested at SNOLAB
• Cheers to 10 years! How research with yeast is creating a new brew and helping scientists understand radiation

SNOLAB is marking ten years since the multi-lab facility officially opened.

Virtue explained that there has been confusion over the years between SNOLAB and the Sudbury Neutrino Observatory (SNO). The latter was a single experiment which finished data collection in 2006. The research from the SNO experiment received the 2015 Nobel Prize for Physics for Art MacDonald. 

SNOLAB is an expansion to the space built for SNO, and allows a number of different teams to conduct experiments. It's become world-renowned for what it has to offer.

Virtue said there are other similar labs around the world, some built into road tunnels, mountains or other mines

"But SNOLAB is the deepest of all the facilities, and that means it has the lowest flux of cosmic rays that penetrate to that depth," he said, adding that they are able to reduce cosmic rays by a factor of 50 million.

"[Researchers] are looking for very rare things that haven't been seen yet, and simply the cosmic rays are a background to these increasingly sensitive experiments," Virtue said.

Using space at SNOLAB has become sought after by scientists from around the world to conduct experiments in particle astrophysics, geology, biology and quantum computing.

"There's lots of things that can be done in the underground environment," Virtue said.

Biology experiments at SNOLAB

"SNOLAB is really the only place in Canada that we can do those experiments," said Christopher Thome who is part of the REPAIR Project . That stands for Researching the Effects of the Presence and Absence of Ionizing Radiation.

It examines the role of low-level, natural background ionizing radiation, which Thome explains we are exposed to daily from sources like cosmic rays from space, and isotopes from soils and rocks. Depending on the results, it would help to understand the role of ionizing radiation in cancer.

The team is in the early stages of the experiment and works with cell line, fruit flies and yeast. 

"In order to conduct those experiments you need a facility like SNOLAB where you can go deep underground to shield out from that cosmic radiation."

Future generation experiments

Virtue said the 'hot topic' in the field right now is the search for what is called neutrinoless double-beta decay . 

"It's also the future of SNOLAB."

"That's what makes SNOLAB the lab of the future because we are absolutely the best location in the world for these future generation experiments."

• Audio Nobel Prize winner says Laurentian's physics program cut means losing great minds, research funds
• $12M in provincial funding to allow Sudbury's SNOLAB to 'invest in people'

With its reputation among scientists it means the facility seeks out large amounts of funding from the federal and provincial governments to help with operations. The facility's funding cycle runs from 2023-2029.

"The Canada Foundation for Innovation has a tough job because there are lots of requests for money available in their envelope for these kinds of projects."

"SNOLAB is effectively asking for almost 20 per cent of everything that is available."

SNOLAB is also nearing the end of its search for a new executive director. Virtue said there should be news within the next month or two.

ABOUT THE AUTHOR

Angela Gemmill is a CBC journalist who covers news in Sudbury and northern Ontario. Connect with her on Twitter @AngelaGemmill. Send story ideas to [email protected]

• SNOLAB craft brew
• Material Compatibility Studies
• Gadolinium Doped Water Detectors
• Water Based Liquid Scintillator

SNO+ is a multiphase experiment with the end goal of looking for neutrinoless double beta decay with 130 Te. The experiment is an extension of the original SNO (Sudbury Neutrino Observatory) experiment, replacing the heavy water from SNO with liquid scintillator doped with 130 Te. SNO+  will run in three distinct phases which each allows for the study of different physics topics. The first is a pure water phase which will be sensitive to a unique mode of baryon number violating nucleon decay. The second is a pure scintillator phase which will be sensitive to solar and neutrino oscillation physics, as well as provide an excellent measurement of the detector systematic uncertainties and backgrounds. The final phase centers on the search for neutrinoless double beta decay by adding the 130 Te.

The picture shown on the right is a side view taken with an underwater camera during the water phase filling. One can see the Acrylic Vessel hanging from the upper deck, and the surrounding 10,000 8-inch PMTs.

The Search Baryon Number Violation

Baryon number is a symmetry that essentially says that quarks and leptons do not have interactions that change one into the other directly. For example, a proton (baryon number = 1 ) will not spntaneously decay into an  e +  and π 0   (baryon number = 0). Since theories that unify quarks and leptons usually have such interactions, there are theoretical motivations to look for rare decays like this. 

For the SNO+ water phase, we have oxygen nuclei without the pesky background from  D 2 O, rejection of reactor events via neutron tagging, and solar neutrino electron scattering background reduction via directional imaging. Thus, even in a short water phase (3-6 month) we expect to significantly improve on the KamLAND result. Stay tuned for a result in 2018!

Measurement of Mixing Parameters using Nuclear Reactors

Nuclear reactors used for power around the world are major emitters of electron antineutrinos.  These electron antineutrinos are weakly interacting and mostly pass through matter undetected.  However, large detectors filled with proton-dense materials can detect these antineutrinos through the inverse beta decay (IBD) process.  In an IBD interaction, an electron neutrino hits a proton, producing a neutron and a positron.  A double coincidence signal, produced by light emitted from the positron and neutron’s interactions with SNO+’s organic scintillator, can be easily detected using the PMTs. 

Measurements of neutrino oscillation parameters have been made through observation of reactor antineutrinos (KamLAND[1]) and solar neutrinos (SNO[2], Super Kamiokande[3]).  Upgraded electronics and better calibration/analysis techniques have recently improved solar neutrino oscillation measurements made by the Super Kamiokande detector.  The Super Kamiokande collaboration measured the delta-m squared oscillation parameter, defined as the difference of the first neutrino mass squared and second neutrino mass squared.  The results indicate a ~2 sigma difference between solar and reactor experimental measurements of the delta-m squared oscillation parameter.

  Due to the location of these power plants, SNO+’s antineutrino spectrum shape is sensitive to changes in the oscillation parameters .   We will analyze the antineutrino spectrum shape in SNO+ to provide more data on the present tension in solar and reactor neutrino oscillation measurements. The plot on the right shows the expected antineutrino energy spectrum in SNO+ per MeV for 10 32 proton-years of exposure for reactors at the Bruce complex at 240 km (blue), Darlington and Pickering complexes at 350 km (red), and all other reactors (yellow). The grey lines show the unoscillated spectra, plus the expected geoneutrino contribution. SNO+ expects roughly 90 events/year,  and thus will be able to make a measurment of   Δm 2 12 to a sensitivity of 0.2x10 -5 eV 2 in about 7 years. This is similar to KamLAND sensitivity, which will help to resolve the current tension between the solar and reactor results.   

The Search for Neutrinoless Double Beta Decay

  One of the most interesting questions in particle physics is whether or not neutrinos are fundamentally different than other particles because they have a so-called " Majorana Solution ." In this scenario, neutrinos are basically their own anti-particle and it is possible that they could mediate neutrinoless  double beta decay. 

SNO+ as a Media Phenomenon!

We have our own craft brew !

...and our own Recruiting Video!

...and Spiderman is a SNO+ Collaborator !

References:

 [1] K. Eguchi  et al.  (KamLAND Collaboration), “First Results from KamLAND: Evidence for Reactor Antineutrino Disappearance”, Phys. Rev. Lett. 90, 021802 (2003). [2] B. Aharmin et al.,” Combined analysis of all three phases of solar neutrino data from the Sudbury Neutrino Observatory”, Phys. Rev. C 88, 025501 (2013). [3] K. Abe  et al.  (Super-Kamiokande Collaboration), “Solar neutrino measurements in Super-Kamiokande-IV”, Phys. Rev. D 94, 052010, (2016). [4] S. Andringa, E. Arushanova, et al. “Current Status and Future Prospects of the SNO+ Experiment”, Advances in High Energy Physics, Volume 2016, Article ID 6194250 (2016).

[5] h. ejiri, " nuclear deexcitations of nucleon holes associated with nucleon decays in nuclei" phys.  rev. c 48, 1142 (1993)..

Discovering SNOLAB: ten years of underground science

By Eloise Chakour, Physics & Astronomy editor

SNOLAB, Canada’s deep underground research laboratory, celebrated its 10th anniversary this year. Located two kilometres deep in a mine near Sudbury, Ontario, this facility hosts the world’s deepest, cleanest laboratory space. Over the past decade, SNOLAB has been at the forefront of astroparticle physics research and physicists anticipate an equally illustrious future. In this first installation of a two-part series, we explore what SNOLAB is, what it has accomplished, and what we can expect from it in the future.

SNOLAB at a Glance

The name “SNOLAB” refers to both a research facility and the scientific collaboration that works there. The facility has two main areas: its underground laboratory space and a surface-level area to support it. Best known for its work on dark matter detection and neutrinos, SNOLAB currently hosts 11 active experiments in areas ranging from genetics to the testing of scientific measurement equipment . The underground facilities are located in an active mine , which may seem like an odd choice. However, its unique location uses the natural shielding properties of the Earth’s crust. The roughly two kilometres of rock surrounding the laboratory significantly reduce the ambient cosmic rays and other radiation that would otherwise interfere with detectors. Despite being located in an active mine, the underground facility boasts 5000 m 2 of clean room space, with air contaminants like dust filtered out to a maximum specified density to further reduce sources of interference with measurement equipment. Particle and radiation detectors are particularly sensitive to background-related noise.

SNOLAB was officially launched in 2012, although an experiment called SNO – Sudbury Neutrino Observatory – was already at that location. SNOLAB was built as an expansion of the experiment’s infrastructure and is currently host to SNO’s successor, SNO+.

Science at SNOLAB

SNOLAB broadly classifies its research into four research focus topics : low background environments, dark matter, neutrinos, and diverse inquiry.

Low background environments

Low background environments are environments where all the sources of signal noise external to the experiment, like dust, cosmic rays, and radiation, are minimized by shielding, air filtration, and other manipulations of the experimental environment. This research focus topic therefore stems directly from the facility’s unique design and location. What better place to study such environments than the deepest, cleanest lab in the world? While all SNOLAB experiments take advantage of the facility’s built-in low background in some way, the REPAIR experiment, currently in progress, was designed specifically to do so. A team of biologists set up shop in the underground facility to study how living in a low background environment affects organisms.

Dark matter

The DEAP-3600 detector during its construction. Image : SNOLAB, approved media image.

Dark matter, SNOLAB’s second focus topic, is one of physics’ biggest mysteries today. Simply put, there is a lot more “stuff” in the universe than we can detect and account for. The matter that we can’t detect is referred to as dark matter. Why do we call it dark? Because we can’t see it! It doesn’t seem to interact with photons and the electromagnetic force (what we call light), which makes it difficult to detect with traditional experimental physics setups. There are many hypotheses concerning dark matter’s nature, but so far, physicists have only been able to rule out a few . SNOLAB has produced some of the strongest experimental data surrounding what dark matter is – and isn’t – and has acted as a key player in the search for dark matter since the lab’s inception. Today, more than half of SNOLAB’s ongoing experiments are dedicated to solving this century-old mystery, including the colossal DEAP-3600 collaboration. Its most recent ground-breaking results conclusively showed that dark matter does not exist within a previously unprobed range of masses, which narrows the range in which physicists need to search for it. More on this in part two.

As for the collaboration’s third focus topic, Art McDonald ’s work on solar neutrinos – small, almost massless particles coming from the sun – is perhaps the best-known science to come from the SNO/SNOLAB infrastructure, since it won him the 2015 Nobel Prize ! Neutrinos are still a significant area of research at SNOLAB. SNO+ has continued to give physicists key insights into neutrinos, such as placing a better limit on invisible nucleon decay. Nucleons – the particles that make up the atom’s nucleus – include protons and neutrons. Currently, it is believed that protons don’t decay into other particles outside the nucleus and that neutrons can only decay in one way. Invisible decay modes are hypothetical ways in which nucleons could decay that would be very difficult to detect. The existence of invisible decay modes would be a strong indicator that there is physics beyond what we understand now, that could change how we think about and organize subatomic particles. The SNO+ result has ruled out invisible decay modes in a specific energy range, bringing physicists closer to either detecting or ruling out these decay modes.

Diverse Inquiry

The last of SNOLAB’s focus topics, diverse inquiry, casts a wide net, allowing scientists to pursue questions across many fields. From deep seismic studies – or the underground analysis of earthquakes – to biology and equipment testing, if it needs to be done deep underground or in a very shielded location, SNOLAB is the place to do it. For example, the PUPS seismic experiment was able to show important ways in which the propagation of earthquake vibrations is different on the surface and deep underground. This information could help increase safety in mining practices, among other applications.

Looking Forward

This image of the SNO+ detector was taken by one of the experiment’s underwater cameras. Image by SNOLAB, approved media image.

In May of this year, the SNO+ experiment finished upgrading its apparatus , which significantly increased the detector’s sensitivity and allowed the team to start a new phase of data collection. These changes will let SNO+ measure the Canadian Shield’s geoneutrinos – neutrinos originating from radioactive decay on Earth – for the very first time.

With its world-class detectors and unique location, physicists expect SNOLAB to provide continued insight into the nature of dark matter in the coming years. A new experiment using the SNO+ neutrino detector to continue the search for dark matter has been suggested , although no plans have been announced yet. Last year , SNOLAB unveiled their Strategic Development Plan for 2023-2029, so it’s safe to say that there are many exciting things in store.

SNOLAB has carved out an influential place for itself in both Canadian and worldwide physics in its 10 years of operation. By continuing and expanding the legacy of SNO, the collaboration has greatly contributed to astroparticle physics and beyond. In part two, we will explore the science involved in some of SNOLAB’s active experiments.

Editor’s note: This post is the first of a 2-part series by Eloise Chakour about SNOLASB. To read Part 2, click here .

Feature image: SNOLAB’s aboveground facilities. Photo : Phil Harvey, CC0 1.0.

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This Underground Lab in Sudbury Is Studying the Smallest Particle in the World

Sudbury , Ontario is home to the only laboratory of its kind in Canada: SNOLAB . The origin of this fascinating underground laboratory goes back to 1998 when scientists conducted experiments in an endless quest to understand fundamental particles of the universe (namely neutrinos and dark matter).

What’s remarkable is that SNOLAB is located 2000 metres below ground. Yes, you read that right – a full two kilometres. You would have to stack four CN Towers on top of one another to reach the depth of the laboratory. There is actually an asteroid named after it, so it’s got to be cool! 

First, A Little Background on the Neutrino

You can’t see neutrinos with the naked eye, but in one second, billions of solar neutrinos pass through your thumbnail. The sun and other stars produce these subatomic particles, which are the smallest particles in the universe.  

Ever since neutrinos were first directly detected in 1956, scientists have tried to understand them because they hold the answer to the evolution and fate of the sun, which in turn relates to life on earth. A significant step forward in this quest was the Homestake Experiment . From 1970 to 1994, a detector in an underground mine in South Dakota measured neutrinos. The goal was to measure the number of solar neutrinos reaching Earth. But there was a significant discrepancy between the number of neutrinos detected and the number predicted by theoretical calculations. This discrepancy was known to the scientific world  as “The Solar Neutrino Problem.” 

Why Is SNOLAB In Sudbury? It's All About the Mining. 

The hunt was on for solutions to the solar neutrino problem. Japan, Italy, and the former Soviet Union all looked for a solution. And Canada soon became part of this quest. By the 1980s, Sudbury was a place of innovation. In 1971, astronauts from Apollo 16 trained in town before their lunar mission. In 1978, a regreening program was initiated in town, followed by the opening of Science North in 1984. An international team of scientists, educational institutions, and scientific organizations, called the “SNO collaboration,” researched INCO’s nickel and copper mine in Creighton, a community outside of Sudbury.

The mine was the deepest of its kind in the world. Managers at the mine were open to hosting a physics experiment, and, as a result, the SNO experiment was established. Two thousand metres of rock would protect lab experiments from cosmic rays, hugely reducing background radiation levels.

How'd They Build SNOWLAB Exactly? 

Engineers created a 12-metre diameter spherical acrylic vessel below ground. The vessel was bonded together underground from 125 pre-formed panels (since all detector components had to fit into the mine cage!) Atomic Energy of Canada lent 1,000 tonnes of heavy water that would be used to observe three separate neutrino reactions. This would allow scientists to understand if solar neutrinos changed flavour as they travelled to the Earth.

A 10-story cavern was created to host the experiment. (In the photo above, you’ll see the scale in comparison to a person walking on the access deck). Access to this massive cavern was through a passageway called "SNO DRIFT" that was set away from the active mining area to help isolate the experiment from any vibrations caused by mining activity. The SNO drift also included operations equipment and personnel facilities – all in a cleanroom setting. If you’re wondering what this means, think clean in every way possible! 

The Early Days of the Sudbury Neutrino Observatory (1998-2006)    

The SNO collaboration included experts from around the world, including Dr. Art Macdonald , an astrophysics professor from Queen’s University. After nine years of construction, SNO began operations on April 28th, 1998. World-renowned theoretical physicist Dr. Stephen Hawking spoke before a delighted crowd. "Neutrinos are mysterious and elusive particles, yet they may make up 90 per cent of the density of the Universe. It all depends on their mass, which is one of the things that S-N-O will measure. Let's hope the neutrinos cooperate by turning up and having a mass in the interesting range.”

Hawking was right. In 2001, SNO scientists published a paper showing that neutrinos change flavour on their journey to Earth. As a result, the 2015 Nobel Prize in Physics was co-awarded to  Dr. Art McDonald and  Dr. Takaki Kajita (from Japan’s Super-Kamiokande detector) for the discovery that neutrinos change identities and therefore have mass.

SNOLAB (2012 –) 

Now that the riddle of neutrino oscillations was solved, the SNO facility was expanded into a multi-purpose laboratory. The goal was to further research astroparticle physics and collaborate with other scientists around the world.  SNOLAB opened in 2012 with 3,700 m2 of additional cleanroom space – making it the deepest, cleanest lab in the world. 

What Exactly Happens at SNOLAB?

Over one hundred people work at SNOLAB, including about 50 underground daily. But this is not your typical commute from home. It’s an intricate process that begins at the surface facility in the community of Lively. Here, staff change into underground work clothes, take a 5-10 minute mine cage ride underground, and walk 1.5km through the mine before using the SNOLAB shower facilities and entering the clean lab. 

There are two main research areas and  12 active experiments currently underway. Let’s break them down. 

Neutrinos : In one experiment, SNO + reuses much of the original SNO detector hardware, which is filled with a liquid scintillator to detect neutrinos from various sources. When a neutrino hits the detector, light is created. HALO is a supernova detector designed to observe neutrinos from supernovae in our observable galaxy. 

Dark Matter : This term refers to matter in space that’s never been seen before (85% of all the matter in the Universe is dark matter!). It’s nearly impossible to detect directly because dark matter doesn’t interact with the electromagnetic spectrum. 

SuperCDMS uses silicon and germanium crystals held just above absolute zero to look for dark matter. When a particle interacts, it creates a detectable vibration in the crystals.

In addition to neutrino and dark matter studies, some biology experiments take advantage of the unique environment underground. FLAME looks at how the increased pressure from 2 km of rock underground affects metabolism. REPAIR studies the effect of very low background radiation on living organisms. 

Can You Visit SNOLAB? Sort Of!

There’s a lot more to SNOLAB than what’s underground.  Science North , near downtown Sudbury, has a  4th Floor  exhibit area, Space Place, where you can learn about space and the search for dark matter. You can watch trails of particles zipping past in real-time at the cloud chamber, explore a model of SNOLAB, and take a virtual 360° tour of the facility. Hear from scientists from around the world who work at SNOLAB in Between the Stars: a fun 15-minute theater experience with special effects and cool objects. 

If you’re a student in Sudbury, there’s a good chance that you've seen the SNOLAB exhibits at Science North or had a presentation from the Education and Outreach team. Even though SNOLAB is not open to the public because it’s located in an active mine site, undergraduate and graduate students studying physics can apply to join summer school programs. During Covid, they’re taking place virtually, so students, keep an eye out for application deadlines for summer 2022 ! SNOLAB also has a post-secondary student hiring program with work opportunities in the underground lab, surface facility, and some offered remotely.

There are ties to SNOLAB at places you may least expect. On Minto Street is the Old Rock Coffee Roaster that serves a special brew called Dark Matter Coffee . We don’t think it was made with neutrinos (although they will certainly be passing through it), but it’s certainly a neat story to tell friends how it was named. 

Believe it or not, there’s also SNOLAB-themed beer available at 46 North . One of its brews, Cosmic Rays , is made with yeast that was cultured in the lab! 

Howo To Enjoy Snolab From Your Living Room   

During these long pandemic days and nights, why not learn about SNOLAB from home?  The easiest way to get acquainted is to explore  the virtual tour (or the guided tour with  Dr. Art Macdonald ). Next, to understand the type of research being conducted, visit SNOLAB’S outreach page with educational videos such as “How to build a dark matter detector” To stay up to date, check out SNOLAB’s social media channels @SNOLABscience.

An engaging artist residency project,  “Drift: Art and Dark Matter,” was created through a joint partnership with Queen’s University’s McDonald Institute and the Agnes Etherington Art Gallery. You won’t want to miss this project at the Art Gallery of Sudbury .

SNOLAB has become part of the fabric of Sudbury – dedicated to elevating scientific excellence in Canada and abroad. 

Blaire Flynn and Jenna Saffin from the Education and Outreach Department at SNOLAB, contributed substantially to this article. The author wishes to thank them for their time and expertise.

Find more things to do and places to stay in Sudbury!

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Maya Bilbao is passionate about the history of Canada. Her work as a researcher and writer has been featured on CBC, PBS, Rogers-TV, and The Canadian Encyclopedia, among other media. She loves hiking, photography, classic jazz, anything invention-related, and finding the best possible decadent dark chocolate around. 

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