From University of Pennsylvania: “Answering big questions by studying small particles”

U Penn bloc

From University of Pennsylvania

April 8, 2019

Erica K. Brockmeier-Writer
Eric Sucar- Photographer

1
A view inside the SNO detector, a 40-foot acrylic sphere that’s covered with thousands of photodetectors. The facility is located in SNOLAB, a research facility located 2km underground near in the Vale’s Creighton nickel mine, Sudbury, Canada (Photo credit: SNO+ Collaboration).

Neutrinos are extremely lightweight subatomic particles that are produced during nuclear reactions both here on Earth and in the center of stars. But neutrinos aren’t harmful or radioactive: In fact, nearly 100 trillion neutrinos bombard Earth every second and usually pass through the world without notice.

Joshua Klein is an experimental particle physicist who studies neutrinos and dark matter. His group, along with retired professor Eugene Beier, collaborates with the Sudbury Neutrino Observatory (SNO), an international research endeavor focused on the study of neutrinos. Klein and Beier’s groups previously designed and now maintain the electronics at SNOLAB that collect data on these subatomic particles.

Klein is fascinated by neutrinos and how they could help answer fundamental questions about the nature of the universe. “They may explain why the universe is made up of matter and not equal parts matter and anti-matter, they may be responsible for how stars explode, they may even tell us something about the laws of physics at the highest energy scales,” says Klein.

Previous research on neutrinos has already led to groundbreaking discoveries in particle physics. The SNO collaboration was awarded the 2016 Breakthrough Prize in Fundamental Physics for solving the “solar neutrino problem.” The problem was that the number of neutrinos being produced by the sun was only a third of what was predicted by theoretical physicists, a discrepancy that had puzzled researchers since the 1970s.

To solve this, researchers went about 1.2 miles underground to study neutrinos in order to avoid the cosmic radioactive particles that could interfere with their minute and precise measurements. The SNOLAB facility in Sudbury, Canada, which houses a a 40-foot wide acrylic vessel surrounded by photodetectors, allowed physicists to measure the three different types of neutrinos at the same time. Physicists found that neutrinos were able to change from one type into another.

2
The exterior of the SNO Detector as seen from the ground at SNOLAB (Photo credit: SNOLAB).

Today, 15 years later, researchers are looking for an incredibly rare process involving neutrinos that, if found, could revolutionize the field of fundamental physics. “Now that we know that neutrinos can change form, along with the fact that neutrinos have mass but no charge, we can hypothesize that they can be their own antiparticle. If this is true, it could explain why the universe is made of only matter,” says Klein.

The question of what happened to all the antimatter has remained unanswered since Paul Dirac won the Nobel Prize in 1933 after calculating that every particle in the universe must have a corresponding antiparticle. But the majority of the universe is made of ordinary matter, not equal parts matter and anti-matter, and scientists are trying to figure out why.

The photodetectors at SNOLAB are now being upgraded as part of SNO+ [Physical Review D] in order to search for a rare type of radioactive decay known as a neutrinoless double beta decay, a never-before seen process that would prove that neutrinos and anti-neutrinos are actually the same particle. Witnessing a neutrinoless double-beta decay event is so rare, if it even exists, and would give off such a small signal that the only way to detect it is through the combination of powerful equipment, refined analyses, and a lot of patience.

Instead of sitting around waiting for a rare event to happen, researchers are actively taking advantage of this state-of-the-art underground facility. “One of the selling points of SNO+ is that it’s a multipurpose detector,” says graduate student Eric Marzec. “A lot of detectors are produced with a singular goal, like detecting dark matter, but SNO+ has a lot of other interesting physics that it can probe.”

3
4
5
6
Here at Penn, students from the Klein lab conduct key maintenance and repairs on the electronic components that are instrumental to the success of SNO+. They also conduct research on new materials that can help increase the sensitivity of the detector, providing more chances of seeing a rare neutrinoless double-beta decay event. (Four photos, no individual descriptions.)

Marzec and Klein were part of a recent study using SNO+’s upgraded capabilities to collect new data on solar neutrinos [Physical Review D]. Before the detector vessel is filled with scintillator, a soap-like liquid that will help them detect rare radioactive decays, it was briefly filled with water. This enabled researchers to collect data on what direction the neutrinos came from, which then allowed them to focus their efforts on studying neutrinos that came from the Sun.

The solar neutrino problem may be solved, but new data on solar neutrinos is still incredibly useful, especially since data from SNO+ have very low background signals from things like cosmic radiation. “There’s only a few experiments that have ever been able to measure neutrinos coming from the sun,” says Marzec. “People might someday want to look at whether the neutrino production of the sun varies over time, so it’s useful to have as many time points and as many measurements over the years as possible.”

Marzec has spent a considerable amount of time working at the SNOLAB facility in northern Ontario. He describes a typical day as starting with a 6 a.m. underground elevator ride that travels more than a mile underground. SNOLAB researchers share the elevator with miners on their way to work in the Vale’s Creighton nickel mine. “All the miners get very dirty, but all the SNOLAB people are clean, so the difference between them is stark. It’s very obvious who is the nerd underground and who the miners are,” says Marzec.

7
After traveling 6,800 floors underground, researchers walk more than half a mile through a series of tunnels to reach the entrance of SNOLAB (Photo credit: SNOLAB).

After arriving at the –6,800th floor, researchers walk more than a half mile from the cage shaft to the SNOLAB through underground dirt tunnels. When they reach the lab, they have to shower and change into threadless uniforms to prevent any microscopic threads from getting inside the sensitive detector. After air quality checks are completed, the researchers are free to begin their work on the detector.

When asked what it’s like to work more than a mile underground, Marzec comments that he got used to the strangeness after a few visits. “The first time, it feels very much like you’re underground because the pressure is very noticeable, and you feel exhausted at the end of the day.” Thankfully, Marzec and his colleagues don’t have to travel a mile underground every time they want to collect data from SNO+ since they can remotely collect and analyze the hundreds of terabytes of data generated by the detector.

8
To do any repair work or cleaning inside the detector, researchers must be lowered into the 40 foot tall sphere using a harness (Photo credit: SNOLAB).

As Marzec is in the final stages of preparing his Ph.D. thesis, he says he will miss his time working on SNO+. “It’s kind of monastic,” Marzec says about his time working at SNOLAB. “You go there and mediate on physics while you’re there. But it’s also kind of a social thing as well: There are a lot of people you know who are working on the same stuff.”

Klein and his group, including four graduate students and two post-docs, recently returned from a SNOLAB collaboration meeting, where upwards of 100 physicists met to present and discuss recent results and the upcoming plans for the next phase of the project. Klein is excited, and, admittedly, a little bit nervous, to see how everything comes together. “Putting in the liquid scintillator will change everything—there’s never been a detector being converted from a water-based detector to a scintillator detector. Here at Penn, for us, it’s big because we designed upgrades to the electronics to handle the fact that we will be getting data at a rate that’s about 100 times higher,” says Klein.

9
A scientist works inside the SNO+ detector while it is partially filled with deuterated water. Each one of the gold-colored circles is an individual photodetector (Photo credit: SNOLAB).

Despite the numerous technical and logistical challenges ahead, researchers are enthusiastic about the potential that SNO+ can bring to particle physics research. Other areas of study include learning how neutrinos change form, studying low-energy neutrinos to figure out why the Sun seems to have less “heavy” elements than astronomers expect, and measuring geoneutrinos to figure out why Earth is hotter than other nearby planets like Mars.

But for Klein, the prospect of finding a rare neutrinoless double beta decay event remains the most thrilling aspect of this research, which, if discovered, could turn the Standard Model of particle physics on its head. “After the question of what is dark energy and what is dark matter, the question of whether neutrinos are their own antiparticle is the most important question for particle physics to answer,” Klein says. “And if neutrinos are their own antiparticle, the simplest piece you can put into the equation [within the Standard Model] blows up: It doesn’t work, it’s mathematically inconsistent. And we don’t know how we would fix that. It is a completely experimental question, so that’s why we’re excited.”

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

U Penn campus

Academic life at Penn is unparalleled, with 100 countries and every U.S. state represented in one of the Ivy League’s most diverse student bodies. Consistently ranked among the top 10 universities in the country, Penn enrolls 10,000 undergraduate students and welcomes an additional 10,000 students to our world-renowned graduate and professional schools.

Penn’s award-winning educators and scholars encourage students to pursue inquiry and discovery, follow their passions, and address the world’s most challenging problems through an interdisciplinary approach.

#all-the-miners-get-very-dirty-but-all-the-snolab-people-are-clean-so-the-difference-between-them-is-stark, #basic-research, #neutrinoless-double-beta-decay, #neutrinos, #paul-dirac-won-the-nobel-prize-in-1933-after-calculating-that-every-particle-in-the-universe-must-have-a-corresponding-antiparticle, #sno, #sno-sudbury-neutrino-observatory, #snolab, #snolab-researchers-share-the-elevator-with-miners-on-their-way-to-work-in-the-vales-creighton-nickel-mine, #the-question-of-what-happened-to-all-the-antimatter-has-remained-unanswered, #u-pennsylvania

From Live Science: “Could Misbehaving Neutrinos Explain Why the Universe Exists?”

Livescience
From Live Science

October 24, 2018

FNAL’s Don Lincoln

1
Credit: Shutterstock

Scientists revel in exploring mysteries, and the bigger the mystery, the greater the enthusiasm. There are many huge unanswered questions in science, but when you’re going big, it’s hard to beat “Why is there something, instead of nothing?”

That might seem like a philosophical question, but it’s one that is very amenable to scientific inquiry. Stated a little more concretely, “Why is the universe made of the kinds of matter that makes human life possible so that we can even ask this question?” Scientists conducting research in Japan have announced a measurement last month that directly addresses that most fascinating of inquiries. It appears that their measurement disagrees with the simplest expectations of current theory and could well point toward an answer of this timeless question.

Their measurement seems to say that for a particular set of subatomic particles, matter and antimatter act differently.

Matter v. Antimatter

Using the J-PARC accelerator, located in Tokai, Japan, scientists fired a beam of ghostly subatomic particles called neutrinos and their antimatter counterparts (antineutrinos) through the Earth to the Super Kamiokande experiment, located in Kamioka, also in Japan.

J-PARC Facility Japan Proton Accelerator Research Complex , located in Tokai village, Ibaraki prefecture, on the east coast of Japan

Super-Kamiokande experiment. located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan

This experiment, called T2K (Tokai to Kamiokande), is designed to determine why our universe is made of matter. A peculiar behavior exhibited by neutrinos, called neutrino oscillation, might shed some light on this very vexing problem.

T2K map, T2K Experiment, Tokai to Kamioka, Japan

Asking why the universe is made of matter might sound like a peculiar question, but there is a very good reason that scientists are surprised by this. It’s because, in addition to knowing of the existence of matter, scientists also know of antimatter.

In 1928, British physicist Paul Dirac proposed the existence of antimatter — an antagonistic sibling of matter. Combine equal amounts of matter and antimatter and the two annihilate each other, resulting in the release of an enormous amount of energy. And, because physics principles usually work equally well in reverse, if you have a prodigious quantity of energy, it can convert into exactly equal amounts of matter and antimatter. Antimatter was discovered in 1932 by American Carl Anderson and researchers have had nearly a century to study its properties.

However, that “into exactly equal amounts” phrase is the crux of the conundrum. In the brief moments immediately after the Big Bang, the universe was full of energy. As it expanded and cooled, that energy should have converted into equal parts matter and antimatter subatomic particles, which should be observable today. And yet our universe consists essentially entirely of matter. How can that be?

By counting the number of atoms in the universe and comparing that with the amount of energy we see, scientists determined that “exactly equal” isn’t quite right. Somehow, when the universe was about a tenth of a trillionth of a second old, the laws of nature skewed ever-so-slightly in the direction of matter. For every 3,000,000,000 antimatter particles, there were 3,000,000,001 matter particles. The 3 billion matter particles and 3 billion antimatter particles combined — and annihilated back into energy, leaving the slight matter excess to make up the universe we see today.

Since this puzzle was understood nearly a century ago, researchers have been studying matter and antimatter to see if they could find behavior in subatomic particles that would explain the excess of matter. They are confident that matter and antimatter are made in equal quantities, but they have also observed that a class of subatomic particles called quarks exhibit behaviors that slightly favor matter over antimatter. That particular measurement was subtle, involving a class of particles called K mesons which can convert from matter to antimatter and back again. But there is a slight difference in matter converting to antimatter as compared to the reverse. This phenomenon was unexpected and its discovery led to the 1980 Nobel prize, but the magnitude of the effect was not enough to explain why matter dominates in our universe.

Ghostly beams

Thus, scientists have turned their attention to neutrinos, to see if their behavior can explain the excess matter. Neutrinos are the ghosts of the subatomic world. Interacting via only the weak nuclear force, they can pass through matter without interacting nearly at all. To give a sense of scale, neutrinos are most commonly created in nuclear reactions and the biggest nuclear reactor around is the Sun. To shield one’s self from half of the solar neutrinos would take a mass of solid lead about 5 light-years in depth. Neutrinos really don’t interact very much.

Between 1998 and 2001, a series of experiments — one using the Super Kamiokande detector, and another using the SNO detector in Sudbury, Ontario ­­— proved definitively that neutrinos also exhibit another surprising behavior. They change their identity.

SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


SNOLAB, Sudbury, Ontario, Canada.

Physicists know of three distinct kinds of neutrinos, each associated with a unique subatomic sibling, called electrons, muons and taus. Electrons are what causes electricity and the muon and tau particle are very much like electrons, but heavier and unstable.

The three kinds of neutrinos, called the electron neutrino, muon neutrino and tau neutrino, can “morph” into other types of neutrinos and back again. This behavior is called neutrino oscillation.

Neutrino oscillation is a uniquely quantum phenomenon, but it is roughly analogous to starting out with a bowl of vanilla ice cream and, after you go and find a spoon, you come back to find that the bowl is half vanilla and half chocolate. Neutrinos change their identity from being entirely one type, to a mix of types, to an entirely different type, and then back to the original type.

Antineutrino oscillations

Neutrinos are matter particles, but antimatter neutrinos, called antineutrinos, also exist. And that leads to a very important question. Neutrinos oscillate, but do antineutrinos also oscillate and do they oscillate in exactly the same way as neutrinos? The answer to the first question is yes, while the answer to the second is not known.

Let’s consider this a little more fully, but in a simplified way: Suppose that there were only two neutrino types — muon and electron. Suppose further that you had a beam of purely muon type neutrinos. Neutrinos oscillate at a specific speed and, since they move near the speed of light, they oscillate as a function of distance from where they were created. Thus, a beam of pure muon neutrinos will look like a mix of muon and electron types at some distance, then purely electron types at another distance and then back to muon-only. Antimatter neutrinos do the same thing.

However, if matter and antimatter neutrinos oscillate at slightly different rates, you’d expect that if you were a fixed distance from the point at which a beam of pure muon neutrinos or muon antineutrinos were created, then in the neutrino case you’d see one blend of muon and electron neutrinos, but in the antimatter neutrino case, you’d see a different blend of antimatter muon and electron neutrinos. The actual situation is complicated by the fact that there are three kinds of neutrinos and the oscillation depends on beam energy, but these are the big ideas.

The observation of different oscillation frequencies by neutrinos and antineutrinos would be an important step towards understanding the fact that the universe is made of matter. It’s not the entire story, because additional new phenomena must also hold, but the difference between matter and antimatter neutrinos is necessary to explain why there is more matter in the universe.

In the current prevailing theory describing neutrino interactions, there is a variable that is sensitive to the possibility that neutrinos and antineutrinos oscillate differently. If that variable is zero, the two types of particles oscillate at identical rates; if that variable differs from zero, the two particle types oscillate differently.

When T2K measured this variable, they found it was inconsistent with the hypothesis that neutrinos and antineutrinos oscillate identically. A little more technically, they determined a range of possible values for this variable. There is a 95 percent chance that the true value for that variable is within that range and only a 5 percent chance that the true variable is outside that range. The “no difference” hypothesis is outside the 95 percent range.

In simpler terms, the current measurement suggests that neutrinos and antimatter neutrinos oscillate differently, although the certainty does not rise to the level to make a definitive claim. In fact, critics point out that measurements with this level of statistical significance should be viewed very, very skeptically. But it is certainly an enormously provocative initial result, and the world’s scientific community is extremely interested in seeing improved and more precise studies.

The T2K experiment will continue to record additional data in hopes of making a definitive measurement, but it’s not the only game in town. At Fermilab, located outside Chicago, a similar experiment called NOvA is shooting both neutrinos and antimatter neutrinos to northern Minnesota, hoping to beat T2K to the punch.

FNAL NOvA Near Detector


FNAL/NOvA experiment map


FNAL NOvA far detector in northern Minnesota


NOvA Far Detector Block

And, looking more to the future, Fermilab is working hard on what will be its flagship experiment, called DUNE (Deep Underground Neutrino Experiment), which will have far superior capabilities to study this important phenomenon.


FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


SURF DUNE LBNF Caverns at Sanford Lab

While the T2K result is not definitive and caution is warranted, it is certainly tantalizing. Given the enormity of the question of why our universe seems to have no appreciable antimatter, the world’s scientific community will avidly await further updates.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

#antimatter-and-matter, #basic-research, #fnal-lbnf-dune-at-surf, #fnal-nova, #j-parc-accelerator, #neutrinos, #snolab, #super-kamiokande-experiment, #t2k-tokai-to-kamiokande-experiment

From Symmetry: “Dark matter vibes”

Symmetry Mag
From Symmetry

09/20/18
Manuel Gnida

1
Dawn Harmer, SLAC

SuperCDMS physicists are testing a way to amp up dark matter vibrations to help them search for lighter particles.

A dark matter experiment scheduled to go online at the Canadian underground laboratory SNOLAB in the early 2020s will conduct one of the most sensitive searches ever for hypothetical particles known as weakly interacting massive particles, or WIMPs.

SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

Scientists consider WIMPs strong dark matter candidates. But what if dark matter turns out to be something else? After all, despite an intense hunt with increasingly sophisticated detectors, scientists have yet to directly detect dark matter.

That’s why researchers on the SuperCDMS dark matter experiment at SNOLAB are looking for ways to broaden their search. And they found one: They have tested a prototype detector that would allow their experiment to search for much lighter dark matter candidates as well.

SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


SLAC SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


LBNL Super CDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

“This development is exciting because it gives us access to a new sector of particle masses where alternatives to WIMPs could be hiding,” says Priscilla Cushman from the University of Minnesota, spokesperson for the SuperCDMS collaboration. “It also demonstrates the flexibility of our detector technology, now reaching energy thresholds and resolutions that weren’t possible a few years ago.”

The collaboration published the results of the first low-mass dark matter search with the new technology in Physical Review Letters. Some scientists on the team also described the prototype in an earlier paper in Applied Physics Letters.

An ultrasensitive mic for dark matter

The core of the SuperCDMS experiment is made of very sensitive detectors on the top and bottom of hockey puck-shaped silicon and germanium crystals. The detectors are able to observe very small vibrations caused by dark matter particles rushing through the crystals. The challenge in using this technology to find light dark matter particles is that, the lighter the particle, the smaller the vibrations.

“To pick those vibrations up, you need an extraordinary ‘microphone’,” says Matt Pyle from the University of California, who contributed to both papers. “Our goal is to build microphones—detectors—that are sensitive enough to detect signals of very light particles. Our technology is at the leading edge of what’s currently possible.”

The vibrations caused by a dark matter interaction can also dislodge negatively charged electrons in the crystal. This leaves positively charged spots, or holes, at the locations where the electrons once were. If an electric field is applied, the pairs of electrons and holes traverse the crystal in opposite directions, and the detector can measure their charge.

One way of making the experiment more sensitive is to increase the efficiency with which it measures the charge of the electron-hole pairs. This approach has been the major factor in improving sensitivity until now. The predecessor of SuperCDMS SNOLAB—the SuperCDMS Soudan experiment, housed in the Soudan mine in Minnesota—required the charge from 70 electron-hole pairs to make a detection. SuperCDMS SNOLAB will require just half as much.

“But that’s not the type of improvement we did here,” says Roger Romani, a recent undergraduate student in Blas Cabrera’s group at Stanford University and lead author of the Applied Physics Letters paper. The team found a different way to make the experiment even more sensitive.

“In our approach, we counted the number of electron-hole pairs by looking at the vibrations they caused when traveling through our detector crystal,” he says.

To do so, Cabrera’s team, joined by Pyle and Santa Clara University’s Betty Young, applied a high voltage that pushed the electron-hole pairs through the crystal. The acceleration led to the production of more vibrations, on top of those created without voltage.

“As a result, our prototype is sensitive to a single electron-hole pair,” says Francisco Ponce, a postdoctoral researcher on Cabrera’s team. “Being able to measure a smaller charge gives us a higher resolution in our experiment and lets us detect particles with smaller mass.”

4
This refrigeration unit in the Cabrera lab at Stanford keeps the experiment’s detector crystals at nearly absolute zero temperature. Dawn Harmer, SLAC

First search for light dark matter

The SuperCDMS collaboration has used the prototype detector for a first light dark matter search, and the outcome is promising.

“The experiment demonstrates that we’re sensitive to a mass range in which we had no sensitivity at all before,” says Cabrera, former SuperCDMS SNOLAB project director from the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of the Department of Energy’s SLAC National Accelerator Laboratory and Stanford.

Noah Kurinsky, a recent PhD student in Cabrera’s group, says, “Although the technology is in the early stages of its development, we’re able to set limits on the properties of light dark matter and are already competitive to other experiments that operate in the same mass range.”

The result is even more compelling considering the experimental circumstances: Located in Cabrera’s lab in a basement at Stanford, the experiment wasn’t shielded from the unwanted cosmic-ray background (SuperCDMS SNOLAB will operate 6800 feet underground); it used a very small prototype crystal, limiting the size of the signal (SuperCDMS Soudan’s crystals were 1500 times heavier); and it ran for a relatively short time, limiting the amount of data for the analysis (XENON10 had 20,000 times more exposure).

Eventually, the researchers want to scale up the size of their crystal and use it in a future generation of SuperCDMS SNOLAB. However, much more R&D work needs to be done before that can happen.

At the moment, they’re working on improving the quality of the crystal and on better understanding its fundamental physics: for instance, how to deal with a quantum mechanical effect that randomly creates electron-hole pairs for no apparent reason and can cause a background signal that looks exactly like a signal from dark matter.

The team is hopeful that their efforts will lead to new detector designs that continue to make SuperCDMS SNOLAB more powerful, Pyle says: “Then, we’ll have an even better shot at studying unknown dark matter territory.”

See the full article here .


five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Symmetry is a joint Fermilab/SLAC publication.


#an-ultrasensitive-microphone-for-dark-matter, #basic-research, #dark-matter-hunt, #particle-physics, #searching-for-much-lighter-dark-matter-candidates, #snolab, #supercdms-experiment, #symmetry-magazine, #the-predecessor-of-supercdms-snolab-the-supercdms-soudan-experiment-housed-in-the-soudan-mine-in-minnesota-required-the-charge-from-70-electron-hole-pairs-to-make-a-detection-supercdm, #wimps

From Gran Sasso via Motherboard: “The New Hunt for Dark Matter Is Taking Place Under a Mountain”

From Gran Sasso

via

Motherboard

1

Aug 30 2018
Daniel Oberhaus

Davide D’Angelo wasn’t always interested in dark matter, but now he’s at the forefront of the hunt to find the most elusive particle in the universe.

About an hour outside of Rome there’s a dense cluster of mountains known as the Gran Sasso d’Italia. Renowned for their natural beauty, the Gran Sasso are a popular tourist destination year round, offering world-class skiing in the winter and plenty of hiking and swimming opportunities in the summer. For the 43-year old Italian physicist Davide D’Angelo, these mountains are like a second home. Unlike most people who visit Gran Sasso, however, D’Angelo spends more time under the mountains than on top of them.

It’s here, in a cavernous hall thousands of feet beneath the earth, that D’Angleo works on a new generation of experiments dedicated to the hunt for dark matter particles, an exotic form of matter whose existence has been hypothesized for decades but never proven experimentally.

Dark matter is thought to make up about 27 percent of the universe and characterizing this elusive substance is one of the most profound problems in contemporary physics. Although D’Angelo is optimistic that a breakthrough will occur in his lifetime, so was the last generation of physicists. In fact, there’s a decent chance that the particles D’Angelo is looking for don’t exist at all. Yet for physicists probing the fundamental nature of the universe, the possibility that they might spend their entire career “hunting ghosts,” as D’Angelo put it, is the price of advancing science.

WHAT’S UNDER THE ‘GREAT STONE’?

In 1989, Italy’s National Institute for Nuclear Physics opened the Gran Sasso National Laboratory, the world’s largest underground laboratory dedicated to astrophysics. Gran Sasso’s three cavernous halls were purposely built for physics, which is something of a luxury as far as research centers go. Most other underground astrophysics laboratories like SNOLAB are ad hoc facilities that repurpose old or active mine shafts, which limits the amount of time that can be spent in the lab and the types of equipment that can be used.


SNOLAB, Sudbury, Ontario, Canada.

Buried nearly a mile underground to protect it from the noisy cosmic rays that bathe the Earth, Gran Sasso is home to a number of particle physics experiments that are probing the foundations of the universe. For the last few years, D’Angelo has divided his time between the Borexino observatory and the Sodium Iodide with Active Background Rejection Experiment (SABRE), which are investigating solar neutrinos and dark matter, respectively.

Borexino Solar Neutrino detector

SABRE experiment at INFN Gran Sasso

2
Davide D’Angelo with the SABRE proof of concept. Image: Xavier Aaronson/Motherboard

Over the last 100 years, characterizing solar neutrinos and dark matter was considered to be one of the most important tasks of particle physics. Today, the mystery of solar neutrinos is resolved, but the particles are still of great interest to physicists for the insight they provide into the fusion process occurring in our Sun and other stars. The composition of dark matter, however, is still considered to be one of the biggest questions in particle physics. Despite the radically different nature of the particles, they are united insofar as they both can only be discovered in environments where the background radiation is at a minimum: Thousands of feet beneath the Earth’s surface.

“The mountain acts as a shield so if you go below it, you have so-called ‘cosmic silence,’” D’Angelo said. “That’s the part of my research I like most: Going into the cave, putting my hands on the detector and trying to understand the signals I’m seeing.”

After finishing grad school, D’Angelo got a job with Italy’s National Institute for Nuclear Physics where his research focused on solar neutrinos, a subatomic particle with no charge that is produced by fusion in the Sun. For the better part of four decades, solar neutrinos [recently caught at U Wisconsin IceCube at the South Pole] were at the heart of one of the largest mysteries in astrophysics.

IceCube neutrino detector interior


U Wisconsin ICECUBE neutrino detector at the South Pole

The problem was that instruments measuring the energy from solar neutrinos returned results much lower than predicted by the Standard Model, the most accurate theory of fundamental particles in physics.

Given how accurate the Standard Model had proven to be for other aspects of cosmology, physicists were reluctant to make alterations to it to account for the discrepancy. One possible explanation was that physicists had faulty models of the Sun and better measurements of its core pressure and temperature were needed. Yet after a string of observations in the 60s and 70s demonstrated that the models of the sun were essentially correct, physicists sought alternative explanations by turning to the neutrino.

A TALE OF THREE NEUTRINOS

Ever since they were first proposed by the Austrian physicist Wolfgang Pauli in 1930, neutrinos have been called upon to patch holes in theories. In Pauli’s case, he first posited the existence of an extremely light, chargeless particle as a “desperate remedy” to explain why the law of the conservation of energy appeared to be violated during radioactive decay. Three years later, the Italian physicist Enrico Fermi gave these hypothetical particles a name. He called them “neutrinos,” Italian for “little neutrons.”

A quarter of a century after Pauli posited their existence, two American physicists reported the first evidence of neutrinos produced in a fission reactor. The following year, in 1957, Bruno Pontecorvo, an Italian physicist working in the Soviet Union, developed a theory of neutrino oscillations. At the time, little was known about the properties of neutrinos and Pontecorvo suggested that there might be more than one type of neutrino. If this were the case, Pontecorvo theorized that it could be possible for the neutrinos to switch between types.

By 1975, part of Pontecorvo’s theory had been proven correct. Three different types, or “flavors,” of neutrino had been discovered: electron neutrinos, muon neutrinos, and tau neutrinos. Importantly, observations from an experiment in a South Dakota mineshaft had confirmed that the Sun produced electron neutrinos. The only issue was that the experiment detected far fewer neutrinos than the Standard Model predicted.

FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA


FNAL DUNE Argon tank at SURF


Surf-Dune/LBNF Caverns at Sanford



SURF building in Lead SD USA

Prior to the late 90s, there was scant indirect evidence that neutrinos could change from one flavor to another. In 1998, a group of researchers working in Japan’s Super-Kamiokande Observatory observed oscillations in atmospheric neutrinos, which are mostly produced by the interactions between photons and the Earth’s atmosphere.

Super-Kamiokande experiment. located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan

Three years later, Canada’s Sudbury Neutrino Observatory (SNO) provided the first direct evidence of oscillations from solar neutrinos.

Sudbury Neutrino Observatory, no longer operating

This was, to put it lightly, a big deal in cosmological physics. It effectively resolved the mystery of the missing solar neutrinos, or why experiments only observed about a third as many neutrinos radiating from the Sun compared to predictions made by the Standard Model. If neutrinos could oscillate between flavors, this means a neutrino that is emitted in the Sun’s core could be a different type of neutrino by the time it reaches Earth. Prior to the mid-80s, most experiments on Earth were only looking for electron neutrinos, which meant they were missing the other two flavors of neutrinos that were created en route from the Sun to the Earth.

When SNO was dreamt up in the 80s, it was designed so that it would be capable of detecting all three types of neutrinos, instead of just electron neutrinos. This decision paid off. In 2015, the directors of the experiments at Super-Kamiokande and SNO shared the Nobel Prize in physics for resolving the mystery of the missing solar neutrinos.

Although the mystery of solar neutrinos has been solved, there’s still plenty of science to be done to better understand them. Since 2007, Gran Sasso’s Borexino observatory has been refining the measurements of solar neutrino flux, which has given physicists unprecedented insight into the fusion process powering the Sun. From the outside, the Borexino observatory looks like a large metal sphere, but on the inside it looks like a technology transplanted from an alien world.

Borexino detector. Image INFN

In the center of the sphere is basically a large, transparent nylon sack that is almost 30 feet in diameter and only half a millimeter thick. This sack contains a liquid scintillator, a chemical mixture that releases energy when a neutrino passes through it. This nylon sphere is suspended in 1,000 metric tons of a purified buffer liquid and surrounded by 2,200 sensors to detect energy released by electrons that are freed when neutrinos interact with the liquid scintillator. Finally, an outer buffer of nearly 3,000 tons of ultrapure water helps provide additional shielding for the detector. Taken together, the Borexino observatory has the most protection from outside radiation interference of any liquid scintillator in the world.

For the last decade, physicists at Borexino—including D’Angelo, who joined the project in 2011—have been using this one-of-a-kind device to observe low energy solar neutrinos produced by proton collisions during the fusion process in the Sun’s core. Given how difficult it is to detect these chargless, ultralight particles that hardly ever interact with matter, detecting the low energy solar neutrinos would be virtually impossible without such a sensitive machine. When SNO directly detected the first solar neutrino oscillations, for instance, it could only observe the highest energy solar neutrinos due to interference from background radiation. This amounted to only about 0.01 percent of all the neutrinos emitted by the Sun. Borexino’s sensitivity allows it to observe solar neutrinos whose energy is a full order of magnitude lower than those detected by SNO, opening the door for an incredibly refined model of solar processes as well as more exotic events like supernovae.

“It took physicists 40 years to understand solar neutrinos and it’s been one of the most interesting puzzles in particle physics,” D’Angelo told me. “It’s kind of like how dark matter is now.”

SHINING A LIGHT ON DARK MATTER

If neutrinos were the mystery particle of the twentieth century, then dark matter is the particle conundrum for the new millenium. Just like Pauli proposed neutrinos as a “desperate remedy” to explain why experiments seemed to be violating one of the most fundamental laws of nature, the existence of dark matter particles is inferred because cosmological observations just don’t add up.

In the early 1930s, the American astronomer Fritz Zwicky was studying the movement of a handful of galaxies in the Coma cluster, a collection of over 1,000 galaxies approximately 320 million light years from Earth.

Fritz Zwicky, the Father of Dark Matter research.No image credit after long search

Vera Rubin did much of the work on proving the existence of Dark Matter. She and Fritz were both overlooked for the Nobel prize.

Vera Rubin measuring spectra (Emilio Segre Visual Archives AIP SPL)


Astronomer Vera Rubin at the Lowell Observatory in 1965. (The Carnegie Institution for Science)

Using data published by Edwin Hubble, Zwicky calculated the mass of the entire Coma galaxy cluster.

Coma cluster via NASA/ESA Hubble

When he did, Zwicky noticed something odd about the velocity dispersion—the statistical distribribution of the speeds of a group of objects—of the galaxies: The velocity distribution was about 12 times higher than it should be based on the amount of matter in the galaxies.

Inside Gran Sasso- Image- Xavier Aaronson-Motherboard

This was a surprising calculation and its significance wasn’t lost on Zwicky. “If this would be confirmed,” he wrote, “we would get the surprising result that dark matter is present in much greater amount than luminous matter.”

The idea that the universe was made up mostly of invisible matter was a radical idea in Zwicky’s time and still is today. The main difference, however, is that astronomers now have much stronger empirical evidence pointing to its existence. This is mostly due to the American astronomer Vera Rubin, whose measurement of galactic rotations in the 1960s and 70s put the existence of dark matter beyond a doubt. In fact, based on Rubin’s measurements and subsequent observations, physicists now think dark matter makes up about 27 percent of the “stuff” in the universe, about seven times more than the regular, baryonic matter we’re all familiar with. The burning question, then, is what is it made of?

Since Rubin’s pioneering observations, a number of dark matter candidate particles have been proposed, but so far all of them have eluded detection by some of the world’s most sensitive instruments. Part of the reason for this is that physicists aren’t exactly sure what they’re looking for. In fact, a small minority of physicists think dark matter might not be a particle at all and is just an exotic gravitational effect. This makes designing dark matter experiments kind of like finding a car key in a stadium parking lot and trying to track down the vehicle it pairs with. There’s a pretty good chance the car is somewhere in the parking lot, but you’re going to have to try a lot of doors before you find your ride—if it even exists.

Among the candidates for dark matter are subatomic particles with goofy names like axions, gravitinos, Massive Astrophysical Compact Halo Objects (MACHOs), and Weakly Interacting Massive Particles (WMIPs.) D’Angelo and his colleagues at Gran Sasso have placed their bets on WIMPs, which until recently were considered to be the leading particle candidate for dark matter.

Over the last few years, however, physicists have started to look at other possibilities after some critical tests failed to confirm the existence of WIMPs. WIMPs are a class of hypothetical elementary particles that hardly ever interact with regular baryonic matter and don’t emit light, which makes them exceedingly hard to detect. This problem is compounded by the fact that no one is really sure how to characterize a WIMP. Needless to say, it’s hard to find something if you’re not even really sure what you’re looking for.

So why would physicists think WIMPs exist at all? In the 1970s, physicists conceptualized the Standard Model of particle physics, which posited that everything in the universe was made out of a handful of fundamental particles.

The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.


Standard Model of Particle Physics from Symmetry Magazine

The Standard Model works great at explaining almost everything the universe throws at it, but it’s still incomplete since it doesn’t incorporate gravity into the model.

Gravity measured with two slightly different torsion pendulum set ups and slightly different results

In the 1980s, an extension of the Standard Model called Supersymmetry emerged, which hypothesizes that each fundamental particle in the Standard Model has a partner.

Standard model of Supersymmetry DESY

These particle pairs are known as supersymmetric particles and are used as the theoretical explanation for a number of mysteries in Standard Model physics, such as the mass of the Higgs boson and the existence of dark matter. Some of the most complex and expensive experiments in the world like the Large Hadron Collider particle accelerator were created in an effort to discover these supersymmetric particles, but so far there’s been no experimental evidence that these particles actually exist.

LHC

CERN map


CERN LHC Tunnel

CERN LHC particles

Many of the lightest particles theorized in the supersymmetric model are WIMPs and go by names like the gravitino, sneutrino and neutralino. The latter is still considered to be the leading candidate for dark matter by many physicists and is thought to have formed in abundance in the early universe. Detecting evidence of this ancient theoretical particle is the goal of many dark matter experiments, including the one D’Angelo works on at Gran Sasso.

D’Angelo told me he became interested in dark matter a few years after joining the Gran Sasso laboratory and began contributing to the laboratory’s DarkSide experiment, which seemed like a natural extension of his work on solar neutrinos. DarkSide is essentially a large tank filled with liquid argon and equipped with incredibly sensitive sensors. If WIMPs exist, physicists expect to detect them from the ionization produced through their collision with the argon nuclei.

Dark Side-50 Dark Matter Experiment at Gran Sasso

The set up of the SABRE experiment is deliberately similar to another experiment that has been running at Gran Sasso since 1995 called DAMA. In 2003, the DAMA experiment began looking for seasonal fluctuations in dark matter particles that was predicted in the 1980s as a consequence of the relative motion of the sun and Earth to the rest of the galaxy. The theory posited that the relative speed of any dark matter particles detected on Earth should peak in June and bottom out in December.

The DarkSide experiment has been running at Gran Sasso since 2013 and D’Angelo said it is expected to continue for several more years. These days, however, he’s found himself involved with a different dark matter experiment at Gran Sasso called SABRE [above], which will also look for direct evidence of dark matter particles based on the light produced when energy is released through their collision with Sodium-Iodide crystals.

Over the course of nearly 15 years, DAMA did in fact register seasonal fluctuations in its detectors that were in accordance with this theory and the expected signature of a dark matter particle. In short, it seemed as if DAMA was the first experiment in the world to detect a dark matter particle. The problem, however, was that DAMA couldn’t completely rule out the possibility that the signature it had detected was in fact due to some other seasonal variation on Earth, rather than the ebb and flow of dark matter as the Earth revolved around the Sun.

SABRE aims to remove the ambiguities in DAMA’s data. After all the kinks are worked out in the testing equipment, the Gran Sasso experiment will become one half of SABRE. The other half will be located in Australia in a converted gold mine. By having a laboratory in the northern hemisphere and another in the southern hemisphere, this should help eliminate any false positives that result from normal seasonal fluctuations. At the moment, the SABRE detector is still in a proof of principle phase and is expected to begin observations in both hemispheres within the next few years.

When it comes to SABRE, it’s possible that the experiment may disprove the best evidence physicists have found so far for a dark matter particle. But as D’Angelo pointed out, this type of disappointment is a fundamental part of science.

“Of course I am afraid that there might not be any dark matter there and we are hunting ghosts, but science is like this,” D’Angelo said. “Sometimes you spend several years looking for something and in the end it’s not there so you have to change the way you were thinking about things.”

For D’Angelo, probing the subatomic world with neutrino and dark matter research from a cave in Italy is his way of connecting to the universe writ large.

“The tiniest elements of nature are bonded to the most macroscopic phenomena, like the expansion of the universe,” D’Angelo said. “The infinitely small touches the infinitely big in this sense, and I find that fascinating. The physics I do, it’s goal is to push over the boundary of human knowledge.”

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

INFN Gran Sasso National Laboratory (LNGS) is the largest underground laboratory in the world devoted to neutrino and astroparticle physics, a worldwide research facility for scientists working in this field of research, where particle physics, cosmology and astrophysics meet. It is unequalled anywhere else, as it offers the most advanced underground infrastructures in terms of dimensions, complexity and completeness.

LNGS is funded by the National Institute for Nuclear Physics (INFN), the Italian Institution in charge to coordinate and support research in elementary particles physics, nuclear and sub nuclear physics

Located between L’Aquila and Teramo, at about 120 kilometres from Rome, the underground structures are on one side of the 10-kilometre long highway tunnel which crosses the Gran Sasso massif (towards Rome); the underground complex consists of three huge experimental halls (each 100-metre long, 20-metre large and 18-metre high) and bypass tunnels, for a total volume of about 180.000 m3.

Access to experimental halls is horizontal and it is made easier by the highway tunnel. Halls are equipped with all technical and safety equipment and plants necessary for the experimental activities and to ensure proper working conditions for people involved.

The 1400 metre-rock thickness above the Laboratory represents a natural coverage that provides a cosmic ray flux reduction by one million times; moreover, the flux of neutrons in the underground halls is about thousand times less than on the surface due to the very small amount of uranium and thorium of the Dolomite calcareous rock of the mountain.

The permeability of cosmic radiation provided by the rock coverage together with the huge dimensions and the impressive basic infrastructure, make the Laboratory unmatched in the detection of weak or rare signals, which are relevant for astroparticle, sub nuclear and nuclear physics.

Outside, immersed in a National Park of exceptional environmental and naturalistic interest on the slopes of the Gran Sasso mountain chain, an area of more than 23 acres hosts laboratories and workshops, the Computing Centre, the Directorate and several other Offices.

Currently 1100 scientists from 29 different Countries are taking part in the experimental activities of LNGS.
LNGS research activities range from neutrino physics to dark matter search, to nuclear astrophysics, and also to earth physics, biology and fundamental physics.

#basic-research, #borexino-observatory, #borexino-solar-neutrino-detector, #cern-lhc, #dama-project, #dark-matter, #darkside-experiment, #davide-dangelo-physical-scientist, #fritz-zwicky, #laboratori-nazionali-del-gran-sasso-infn, #motherboard, #neutrinos, #particle-physics, #physics, #pobbile-dark-matter-candidates-axions-gravitinos-massive-astrophysical-compact-halo-objects-machos-and-weakly-interacting-massive-particles-wmips, #sabre-sodium-iodide-with-active-background-rejection-experiment, #snolab, #solar-neutrinos-recently-caught-at-u-wisconsin-icecube-at-the-south-pole, #standard-model-of-particle-physics, #super-kamiokande-collaboration, #supersymmetry-susy, #surf-sanford-underground-research-facility, #vera-rubin, #wimps-that-go-by-names-like-the-gravitino-sneutrino-and-neutralino

From Sanford Underground Research Facility: “SD Mines develops radon reduction system for LZ, SuperCDMS”

SURF logo
Sanford Underground levels

From Sanford Underground Research Facility

May 14, 2018
Constance Walter

1
Radon reduction researchers pictured with the machine they designed from left): SD Mines physics graduate student Joseph Street, Richard Schnee, Ph.D., along with lab technicians David Molash and Christine Hjelmfelt. Charles Michael Ray, SD Mines

In the coming months, researchers will begin building the LUX-ZEPLIN dark matter experiment in a surface cleanroom at the Sanford Underground Research Facility (Sanford Lab).

LBNL Lux Zeplin project at SURF

Once the detector is assembled, a team will carefully move the highly sensitive physics equipment to its home on the 4850 Level of Sanford Lab.

But before that can happen, there’s some work that needs to be done to ensure the experiment remains free of backgrounds that could interfere with the results. That’s where Dr. Richard Schnee and a team from the South Dakota School of Mines & Technology come in. Schnee, who is head of the physics department at SD Mines and a collaborator with LZ, heads up the SD Mines team that designed a radon reduction system for the experiment.

“Our detectors need very low levels of radon,” Schnee said. While the radon levels at the 4850 Level are safe for humans, they are too high for sensitive experiments like LZ, which go deep underground to escape cosmic radiation, Schnee explained. “We will take regular air from the facility and the systems will reduce the levels by 1,000 times or more.”

LZ, a second-generation dark matter experiment, will continue the search for WIMPs—weakly interacting massive particles—begun by its much smaller predecessor LUX (Large Underground Xenon), which was named the most sensitive of its kind in 2013 and again in 2016.

U Washington Large Underground Xenon at SURF, Lead, SD, USA

LZ will hold 10 tons of liquid xenon, making it approximately 30 times larger and 100 times more sensitive than LUX.

LZ is designed so that if a dark matter particle collides with a xenon atom, it will produce a flash of light followed by a second flash of light when the electrons produced in the liquid xenon chamber drift to its top. The light pulses, picked up by a series of about 500 photo multiplier tubes lining the massive tank—over four times more than were installed in LUX—will carry the telltale fingerprint of the particles that created them.

Additionally, LZ will include a component not present in LUX—nine acrylic tanks filled with a liquid scintillator will form a veto system around the experiment, allowing researchers to better recognize a WIMP if they see one.

The system designed by the SD Mines team focuses specifically on filtering out radon particles to produce the ultra-pure air needed for the acrylic tanks and other components of LZ located in the same water tank that held LUX. The team is also helping ensure the parts used to build the experiments are relatively free of radon.

“The real problem for these super sensitive dark mater detectors are the radon daughters that are radioactive,” Schnee said. Even miniscule amounts of radioactive particles could contaminate and throw off the experiments—so the work of Schnee and his team is critical.

“We are very excited to have SD Mines as a partner in producing a major component for LZ, a world-leading dark matter experiment,” said Mike Headley, executive director the South Dakota Science and Technology Authority.

LZ is in a global race to discover dark matter. One competitor, SuperCDMS (Cryogenic Dark Matter Search), which will be located at SNOLab in Canada, is using germanium to search for WIMPs. And SD Mines is designing a radon reduction system for that experiment as well, Schnee said.

SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario


SNOLAB, Sudbury, Ontario, Canada.

LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


LBNL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)


LBNL Super CDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

SNOLab is the deepest underground laboratory in North America at 6,800 feet deep. Although the experiments are competitors, Schnee said they actually complement each other as they are searching for dark matter in different areas. To use a metaphor, if dark matter were a lost child in a large cornfield, LZ would be looking in one part of the field, and SuperCDMS would be looking in another. Both projects will begin operations in the early 2020s. SD Mines is one of 26 institutions working on the SuperCDMS and one of 37 institutions working on LZ.

Headley attributes the expanding role of SD Mines’ in research at Sanford Lab and other international experiments to the Ph.D. program in South Dakota. SD Mines and the University of South Dakota offer a joint program and each graduated Ph.D. students in 2017.

“With the implementation of the Ph.D. program in 2012, South Dakota institutions are attracting high-quality professors and students,” Headley said. “It’s impressive to see them deliver such an important component for LZ, but also on other experiments around the world.”

To learn more about the physics program at SD Mines, go to www.sdsmt.edu; to read the full press release about SD Mines work on LZ and SuperCDMS, go to https://www.sdsmt.edu/Research/.

You can learn more about LZ at http://lz.lbl.gov/detector/and SCDMS at https://supercdms.slac.stanford.edu.

See the full article here .

Please help promote STEM in your local schools.
stem

Stem Education Coalition

About us.
The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

Fermilab LBNE
LBNE

#dark-matter-experiments, #lux-zeplin-dark-matter-experiment, #snolab, #supercdms-cryogenic-dark-matter-search, #surf-sanford-underground-research-facility, #wimps-weakly-interacting-massive-particles

From Perimeter Institute: “New centre for astroparticle physics launches in Canada”

Perimeter Institute

From Perimeter Institute

May 10, 2018

Perimeter Institute is among 13 partner organizations contributing to a new national hub of astroparticle physics at Queen’s University in Kingston, Ontario.

Queen’s University has officially launched the Arthur B. McDonald Canadian Astroparticle Physics Research Institute, a national research network dedicated to understanding some of the universe’s deepest mysteries.

The namesake of the institute, Arthur B. McDonald, is the 2015 Nobel laureate in physics for his pioneering neutrino work at SNOLAB, and is a member of Perimeter Institute’s Board of Directors.

SNOLAB, a Canadian underground physics laboratory at a depth of 2 km in Vale’s Creighton nickel mine in Sudbury, Ontario

SNOLAB, Sudbury, Ontario, Canada.

The newly announced institute is the result of a $63.7 million investment from the Government of Canada’s Canada First Research Excellence Fund given to Queen’s University in 2016.

Perimeter Institute is among the five affiliated research organizations and eight universities in partnership with the McDonald Institute. Together, the partners aim to facilitate the exchange of research and ideas at the intersections of cosmology and particle physics.

“Although the dimensions of the particles we are studying are minute, the implications of these discoveries are monumental and fundamental to the very properties of science and our understanding of the formation and evolution of the universe,” said McDonald Institute Scientific Director Tony Noble at the May 8 launch in Kingston.

Perimeter Faculty Chair Luis Lehner said partnering with the McDonald Institute will facilitate “collaborative research in pursuit of answers to some of the deepest mysteries in science, and mutually strengthen the training and educational outreach activities of both institutes.”

Over the past year and a half, the McDonald Institute has appointed a scientific director and recruited 13 new faculty members (out of 15 designated positions) from around the world.

In addition to advancing research into areas such as the mysteries surrounding dark matter and neutrino science, the McDonald Institute has a mandate for scientific outreach and to develop unique undergraduate and graduate student programming and opportunities.

Visit http://www.mcdonaldinstitute.ca for more information.

See the full article here .

Please help promote STEM in your local schools.

STEM Icon

Stem Education Coalition

About Perimeter

Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

#arthur-b-mcdonald-canadian-astroparticle-physics-research-institute, #astronomy, #astrophysics, #basic-research, #cosmology, #particle-physics, #perimeter-institute-of-theoretical-physics, #physics, #snolab

From SLAC Lab: “Construction Begins on One of the World’s Most Sensitive Dark Matter Experiments”


From SLAC Lab

May 7, 2018

Press Office Contact: Andrew Gordon,
agordon@slac.stanford.edu
(650) 926-2282

Written by Manuel Gnida

1
The future SuperCDMS SNOLAB experiment will hunt for weakly interacting massive particles (WIMPs), hypothetical components of dark matter. If a WIMP (white trace) strikes an atom inside the experiment’s detector crystals (gray), it will cause the crystal lattice to vibrate (blue). The collision will also send electrons (red) through the crystal that enhance the vibrations. (Greg Stewart/SLAC National Accelerator Laboratory)

2
The future SuperCDMS SNOLAB experiment will hunt for weakly interacting massive particles (WIMPs), hypothetical components of dark matter. This photo shows one of the experiment’s detector crystals within its protective copper housing. (Andy Freeberg/SLAC National Accelerator Laboratory)

3
SLAC’s Paul Brink handles the SuperCDMS SNOLAB engineering tower. (Chris Smith/SLAC National Accelerator Laboratory)

4
A SuperCDMS SNOLAB detector, fabricated at Texas A&M University. (Matt Cherry/SuperCDMS collaboration/SLAC National Accelerator Laboratory)

5
Dan Bauer (left) and Mark Ruschman in Fermilab’s Lab G , where the SuperCDMS SNOLAB project is preparing to test the cryogenics system for the new experiment. (Reidar Hahn/Fermi National Accelerator Laboratory)

6
Fermilab’s Mark Ruschman tests prototypes for the SuperCDMS SNOLAB cryogenics system. (Reidar Hahn/Fermi National Accelerator Laboratory)

The SuperCDMS SNOLAB project, a multi-institutional effort led by SLAC, is expanding the hunt for dark matter to particles with properties not accessible to any other experiment.

SNOLAB, Sudbury, Ontario, Canada.

The U.S. Department of Energy has approved funding and start of construction for the SuperCDMS SNOLAB experiment, which will begin operations in the early 2020s to hunt for hypothetical dark matter particles called weakly interacting massive particles, or WIMPs. The experiment will be at least 50 times more sensitive than its predecessor, exploring WIMP properties that can’t be probed by other experiments and giving researchers a powerful new tool to understand one of the biggest mysteries of modern physics.

The DOE’s SLAC National Accelerator Laboratory is managing the construction project for the international SuperCDMS collaboration of 111 members from 26 institutions, which is preparing to do research with the experiment.

“Understanding dark matter is one of the hottest research topics – at SLAC and around the world,” said JoAnne Hewett, head of SLAC’s Fundamental Physics Directorate and the lab’s chief research officer. “We’re excited to lead the project and work with our partners to build this next-generation dark matter experiment.”

With the DOE approvals, known as Critical Decisions 2 and 3, the researchers can now build the experiment. The DOE Office of Science will contribute $19 million to the effort, joining forces with the National Science Foundation ($12 million) and the Canada Foundation for Innovation ($3 million).

“Our experiment will be the world’s most sensitive for relatively light WIMPs – in a mass range from a fraction of the proton mass to about 10 proton masses,” said Richard Partridge, head of the SuperCDMS group at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of SLAC and Stanford University. “This unparalleled sensitivity will create exciting opportunities to explore new territory in dark matter research.”

An Ultracold Search 6,800 Feet Underground

Scientists know that visible matter in the universe accounts for only 15 percent of all matter. The rest is a mysterious substance, called dark matter. Due to its gravitational pull on regular matter, dark matter is a key driver for the evolution of the universe, affecting the formation of galaxies like our Milky Way. It therefore is fundamental to our very own existence.

But scientists have yet to find out what dark matter is made of. They believe it could be composed of dark matter particles, and WIMPs are top contenders. If these particles exist, they would barely interact with their environment and fly right through regular matter untouched. However, every so often, they could collide with an atom of our visible world, and dark matter researchers are looking for these rare interactions.

7
The centerpiece of the SuperCDMS SNOLAB experiment will be four detector towers (left), each containing six detector packs. The towers will be mounted inside the SNOBOX (right), a vessel in which the detector packs will be cooled to almost absolute zero temperature. (Greg Stewart/SLAC National Accelerator Laboratory)

In the SuperCDMS SNOLAB experiment, the search will be done using silicon and germanium crystals, in which the collisions would trigger tiny vibrations. However, to measure the atomic jiggles, the crystals need to be cooled to less than minus 459.6 degrees Fahrenheit – a fraction of a degree above absolute zero temperature. These ultracold conditions give the experiment its name: Cryogenic Dark Matter Search, or CDMS. The prefix “Super” indicates an increased sensitivity compared to previous versions of the experiment.

The collisions would also produce pairs of electrons and electron deficiencies that move through the crystals, triggering additional atomic vibrations that amplify the signal from the dark matter collision. The experiment will be able to measure these “fingerprints” left by dark matter with sophisticated superconducting electronics.

The experiment will be assembled and operated at the Canadian laboratory SNOLAB – 6,800 feet underground inside a nickel mine near the city of Sudbury. It’s the deepest underground laboratory in North America. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals.

8
The SuperCDMS dark matter experiment will be located at the Canadian laboratory SNOLAB, 2 kilometers (6,800 feet) underground inside a nickel mine near the city of Sudbury. It’s the deepest underground laboratory in North America. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals. (Greg Stewart/SLAC National Accelerator Laboratory; inset: SNOLAB)

“SNOLAB is excited to welcome the SuperCDMS SNOLAB collaboration to the underground lab,” said Kerry Loken, SNOLAB project manager. “We look forward to a great partnership and to supporting this world-leading science.”

Over the past months, a detector prototype has been successfully tested at SLAC. “These tests were an important demonstration that we’re able to build the actual detector with high enough energy resolution, as well as detector electronics with low enough noise to accomplish our research goals,” said KIPAC’s Paul Brink, who oversees the detector fabrication at Stanford.

Together with seven other collaborating institutions, SLAC will provide the experiment’s centerpiece of four detector towers, each containing six crystals in the shape of oversized hockey pucks. The first tower could be sent to SNOLAB by the end of 2018.

“The detector towers are the most technologically challenging part of the experiment, pushing the frontiers of our understanding of low-temperature devices and superconducting readout,” said Bernard Sadoulet, a collaborator from the University of California, Berkeley.

A Strong Collaboration for Extraordinary Science

In addition to SLAC, two other national labs are involved in the project. Fermi National Accelerator Laboratory is working on the experiment’s intricate shielding and cryogenics infrastructure, and Pacific Northwest National Laboratory is helping understand background signals in the experiment, a major challenge for the detection of faint WIMP signals.

9
Slideshow of SuperCDMS SNOLAB photos. For more images, visit the SuperCDMS SNOLAB photostream on Flickr.

A number of U.S. and Canadian universities also play key roles in the experiment, working on tasks ranging from detector fabrication and testing to data analysis and simulation. The largest international contribution comes from Canada and includes the research infrastructure at SNOLAB.

“We’re fortunate to have a close-knit network of strong collaboration partners, which is crucial for our success,” said KIPAC’s Blas Cabrera, who directed the project through the CD-2/3 approval milestone. “The same is true for the outstanding support we’re receiving from the funding agencies in the U.S. and Canada.”

Fermilab’s Dan Bauer, spokesperson of the SuperCDMS collaboration said, “Together we’re now ready to build an experiment that will search for dark matter particles that interact with normal matter in an entirely new region.”

SuperCDMS SNOLAB will be the latest in a series of increasingly sensitive dark matter experiments. The most recent version, located at the Soudan Mine in Minnesota, completed operations in 2015.

“The project has incorporated lessons learned from previous CDMS experiments to significantly improve the experimental infrastructure and detector designs for the experiment,” said SLAC’s Ken Fouts, project manager for SuperCDMS SNOLAB. “The combination of design improvements, the deep location and the infrastructure support provided by SNOLAB will allow the experiment to reach its full potential in the search for low-mass dark matter.”

For more information on the SuperCDMS SNOLAB project and the SuperCDMS collaboration, check out this website:

SuperCDMS SNOLAB Website

See the full article here .

Please help promote STEM in your local schools.

STEM Icon

Stem Education Coalition

SLAC Campus
SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

#astronomy, #basic-research, #construction-begins-on-one-of-the-worlds-most-sensitive-dark-matter-experiments, #dark-matter, #particle-physics, #physics, #slac-labs, #snolab, #supercdms-snolab-experiment, #wimps-weakly-interacting-massive-particles