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  • richardmitnick 4:54 pm on May 24, 2016 Permalink | Reply
    Tags: , , , , Dark Matter,   

    From Goddard: “NASA Scientist Suggests Possible Link Between Primordial Black Holes and Dark Matter” 

    NASA Goddard Banner

    NASA Goddard Space Flight Center

    May 24, 2016
    Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

    Dark matter is a mysterious substance composing most of the material universe, now widely thought to be some form of massive exotic particle. An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe’s existence, known as primordial black holes. Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year.

    “This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good,” said Alexander Kashlinsky, an astrophysicist at NASA Goddard. “If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun’s mass.”

    In 2005, Kashlinsky led a team of astronomers using NASA’s Spitzer Space Telescope to explore the background glow of infrared light in one part of the sky.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    The researchers reported excessive patchiness in the glow and concluded it was likely caused by the aggregate light of the first sources to illuminate the universe more than 13 billion years ago. Follow-up studies confirmed that this cosmic infrared background (CIB) showed similar unexpected structure in other parts of the sky.

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA)
    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA)

    After masking out all known stars, galaxies and artifacts and enhancing what’s left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors indicate brighter areas.

    This image from NASA’s Spitzer Space Telescope shows an infrared view of a sky area in the constellation Ursa Major.

    The CIB glow is more irregular than can be explained by distant unresolved galaxies, and this excess structure is thought to be light emitted when the universe was less than a billion years old. Scientists say it likely originated from the first luminous objects to form in the universe, which includes both the first stars and black holes.

    In 2013, another study compared how the cosmic X-ray background (CXB) detected by NASA’s Chandra X-ray Observatory compared to the CIB in the same area of the sky.

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    The first stars emitted mainly optical and ultraviolet light, which today is stretched into the infrared by the expansion of space, so they should not contribute significantly to the CXB.

    Yet the irregular glow of low-energy X-rays in the CXB matched the patchiness of the CIB quite well. The only object we know of that can be sufficiently luminous across this wide an energy range is a black hole. The research team concluded that primordial black holes must have been abundant among the earliest stars, making up at least about one out of every five of the sources contributing to the CIB.

    The nature of dark matter remains one of the most important unresolved issues in astrophysics. Scientists currently favor theoretical models that explain dark matter as an exotic massive particle, but so far searches have failed to turn up evidence these hypothetical particles actually exist. NASA is currently investigating this issue as part of its Alpha Magnetic Spectrometer and Fermi Gamma-ray Space Telescope missions.

    AMS-02 Bloc
    NASA/AMS02 device

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    “These studies are providing increasingly sensitive results, slowly shrinking the box of parameters where dark matter particles can hide,” Kashlinsky said. “The failure to find them has led to renewed interest in studying how well primordial black holes — black holes formed in the universe’s first fraction of a second — could work as dark matter.”

    Physicists have outlined* several ways in which the hot, rapidly expanding universe could produce primordial black holes in the first thousandths of a second after the Big Bang. The older the universe is when these mechanisms take hold, the larger the black holes can be. And because the window for creating them lasts only a tiny fraction of the first second, scientists expect primordial black holes would exhibit a narrow range of masses.

    On Sept. 14, gravitational waves produced by a pair of merging black holes 1.3 billion light-years away were captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana.

    Caltech/MIT  Advanced Ligo Hanford, WA, USA installation
    Caltech/MIT Advanced Ligo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector in Livingston, Louisiana
    Caltech/MIT Advanced aLigo detector in Livingston, LA, USA

    This event marked the first-ever detection of gravitational waves as well as the first direct detection of black holes.

    Primordial black holes, if they exist, could be similar to the merging black holes detected by the LIGO team in 2014. This computer simulation shows in slow motion what this merger would have looked like up close. The ring around the black holes, called an Einstein ring, arises from all the stars in a small region directly behind the holes whose light is distorted by gravitational lensing. The gravitational waves detected by LIGO are not shown in this video, although their effects can be seen in the Einstein ring. Gravitational waves traveling out behind the black holes disturb stellar images comprising the Einstein ring, causing them to slosh around in the ring even long after the merger is complete. Gravitational waves traveling in other directions cause weaker, shorter-lived sloshing everywhere outside the Einstein ring. If played back in real time, the movie would last about a third of a second.
    Credits: SXS Lensing
    Access mp4 video here .

    The signal provided LIGO scientists with information about the masses of the individual black holes, which were 29 and 36 times the sun’s mass, plus or minus about four solar masses. These values were both unexpectedly large and surprisingly similar.

    In his new paper**, published May 24 in The Astrophysical Journal Letters, Kashlinsky analyzes what might have happened if dark matter consisted of a population of black holes similar to those detected by LIGO. The black holes distort the distribution of mass in the early universe, adding a small fluctuation that has consequences hundreds of millions of years later, when the first stars begin to form.

    For much of the universe’s first 500 million years, normal matter remained too hot to coalesce into the first stars. Dark matter was unaffected by the high temperature because, whatever its nature, it primarily interacts through gravity. Aggregating by mutual attraction, dark matter first collapsed into clumps called minihaloes, which provided a gravitational seed enabling normal matter to accumulate. Hot gas collapsed toward the minihaloes, resulting in pockets of gas dense enough to further collapse on their own into the first stars. Kashlinsky shows that if black holes play the part of dark matter, this process occurs more rapidly and easily produces the lumpiness of the CIB detected in Spitzer data even if only a small fraction of minihaloes manage to produce stars.

    As cosmic gas fell into the minihaloes, their constituent black holes would naturally capture some of it too. Matter falling toward a black hole heats up and ultimately produces X-rays. Together, infrared light from the first stars and X-rays from gas falling into dark matter black holes can account for the observed agreement between the patchiness of the CIB and the CXB.

    Occasionally, some primordial black holes will pass close enough to be gravitationally captured into binary systems. The black holes in each of these binaries will, over eons, emit gravitational radiation, lose orbital energy and spiral inward, ultimately merging into a larger black hole like the event LIGO observed.

    “Future LIGO observing runs will tell us much more about the universe’s population of black holes, and it won’t be long before we’ll know if the scenario I outline is either supported or ruled out,” Kashlinsky said.

    Kashlinsky leads science team centered at Goddard that is participating in the European Space Agency’s Euclid mission, which is currently scheduled to launch in 2020.

    ESA/Euclid spacecraft
    ESA/Euclid spacecraft

    The project, named LIBRAE, will enable the observatory to probe source populations in the CIB with high precision and determine what portion was produced by black holes.

    *Science paper:
    Primordial Black Holes – Recent Developments

    **Science paper:

    See the full article here.

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA Goddard Campus
    NASA/Goddard Campus

  • richardmitnick 2:35 pm on May 24, 2016 Permalink | Reply
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    From LBL: “Hunting for Dark Matter’s ‘Hidden Valley’ ” Women in Science 

    Berkeley Logo

    Berkeley Lab

    May 24, 2016
    Glenn Roberts Jr.

    Kathryn Zurek (Credit: Roy Kaltschmidt/Berkeley Lab)

    Kathryn Zurek realized a decade ago that we may be searching in the wrong places for clues to one of the universe’s greatest unsolved mysteries: dark matter. Despite making up an estimated 85 percent of the total mass of the universe, we haven’t yet figured out what it’s made of.

    Now, Zurek, a theoretical physicist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), says thanks to extraordinary improvements in experimental sensitivity, “We increasingly know where not to look.” In 2006, during grad school, Zurek began to explore the concept of a new “Hidden Valley” model for physics that could hold all of the answers to dark matter.

    “I noticed that from a model-builder’s point of view that dark matter was extraordinarily undeveloped,” she said. It seemed as though scientists were figuratively hunting in the dark for answers. “People were focused on models of just two classes of dark matter candidates, rather than a much broader array of possibilities.”

    Physicist and author Alan Lightman has described dark matter as an “invisible elephant in the room”—you know it’s there because of the dent it’s making in the floorboards but you can’t see or touch it. Likewise, physicists can infer that dark matter exists in huge supply compared to normal matter because of its gravitational effects, which far exceed those expected from the matter we can see in space.

    Since physicist Fritz Zwicky in 1933 measured this major discrepancy in the gravitational mass of a galaxy cluster, that he concluded was due to dark matter, the search for what dark matter is really made of has taken many forms: from deep-underground detectors to space- and ground-based observatories, balloon-borne missions and powerful particle accelerator experiments.

    While there have been some candidate signals and hints, and numerous experiments have narrowed the range of energies and masses at which we are now looking for dark matter particles, the scientific community hasn’t yet embraced a dark matter discovery.

    3 Knowns and 3 Unknowns about Dark Matter

    What’s known
    1. We can observe its effects.

    2. It is abundant.
    It makes up about 85 percent of the total mass of the universe, and about 27 percent of the universe’s total mass and energy.

    3. We know more about what dark matter is not.

    Increasingly sensitive detectors are lowering the possible rate at which dark mark matter particles can interact with normal matter.
    This chart shows the sensitivity limits (solid-line curves) of various experiments searching for signs of theoretical dark matter particles known as WIMPs (weakly interacting massive particles). The shaded closed contours show hints of WIMP signals. The thin dashed and dotted curves show projections for future U.S.-led dark matter direct-detection experiments expected in the next decade, and the thick dashed curve (orange) shows a so-called “neutrino floor” where neutrino-related signals can obscure the direct detection of dark matter particles. (Credit: Snowmass report, 2013.)

    What’s unknown

    1. Is it made up of one particle or many particles?
    (Credit: Pixabay/CreativeMagic)

    Could dark matter be composed of an entire family of particles, such as a theorized “hidden valley” or “dark sector?”
    2. Are there “dark forces” acting on dark matter?

    Are there forces beyond gravity and other known forces that act on dark matter but not on ordinary matter, and can dark matter interact with itself?
    This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster Abell 3827. The blue structures surrounding the central galaxies are views of a more distant galaxy behind the cluster that has been distorted by an effect known as gravitational lensing. Observations of the central four merging galaxies in this image have provided hints that the dark matter around one of the galaxies is not moving with the galaxy itself, possibly indicating the occurrence of an unknown type of dark matter interaction. (Credit: ESO)

    3. Is there dark antimatter?
    A computerized visualization showing the possible large-scale structure of dark matter in the universe. (Credit: Amit Chourasia and Steve Cutchin/NPACI Visualization Services; Enzo)

    In 2006, as a graduate student at the University of Washington, Zurek and collaborator Matthew J. Strassler, a faculty member, published a paper*, “Echoes of a Hidden Valley at Hadron Colliders,” that considered the possibility of new physics such as the existence of a new group of light (low-mass), long-lived particles that could possibly be revealed at CERN’s Large Hadron Collider, the machine that would later enable the Nobel Prize-winning discovery of the Higgs boson in 2012.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    Some of the scientifically popular hypothetical particle candidates for dark matter are WIMPs (weakly interacting massive particles) and axions (very-low-mass particles). But the possibility of a rich and overlooked mix of light particles was compelling for Zurek, who began to construct models to test out the theory.

    “If you had a low-mass hidden sector, you could ‘stuff’ all kinds of things inside of it,” she said. “That really set me up to start thinking about complex dark sectors, which I did as a postdoc.”

    Looking back to 2008, Zurek said she felt like someone carrying around a sandwich board proclaiming that dark matter could be a stranger, manifold thing than most had imagined. “I was like that little guy with the sign.”

    By coincidence, the so-called “PAMELA anomaly” was revealed that same year; data from the PAMELA space mission in 2008 had found an unexpected excess of positrons, the antimatter counterpart to electrons, at certain energies. This measurement excited physicists as a possible particle signature from the decay of dark matter, and the excess defied standard dark matter theories and opened the door to new ones.

    Now that the concept of “hidden valleys” or “dark sectors” with myriad particles making up dark matter is gaining steam among scientists—Zurek spoke in late April at a three-day “Workshop on Dark Sectors”—she said she feels gratified to have worked on some of the early theoretical models.

    “It’s great in one sense because these ideas really got traction,” Zurek said. “The fact that there were these experimental anomalies, that was sort of a coincidence. As a second- or third-year postdoc, this was like ‘my program’—this was the thing I was pushing. It suddenly got very popular.”

    On an afternoon in late April, Zurek and her student Katelin Schutz sat together waiting to press the button to submit a new paper on a proposal to tease out a signal for light dark matter particles using an exotic, supercooled liquid known as superfluid helium. In the paper, they explain how this form of helium can probe for signals of “super light dark matter,” with an energy signature well below the reach of today’s experiments.

    They are also working with Dan McKinsey, a Berkeley Lab scientist and UC Berkeley physics professor who is a superfluid helium expert, on possible designs for an experiment.

    Most popular theories of WIMPs suggest a mass around 100 times the mass of a proton, a particle found at an atom’s core, for example, but a superfluid helium detector could be sensitive to masses many orders of magnitude smaller, she said.

    Are we any closer to finding dark matter?

    Zurek said she is surprised we haven’t yet made a discovery, but she is encouraged by the increasing sensitivity of experiments, and she said Berkeley Lab has particular expertise in high-precision detectors that will hopefully ensure its role in future experiments.

    “There is a cross-fertilization from different fields of physics that has really blossomed in the last several years,” Zurek also said. She joined Berkeley Lab in 2014 after serving as an associate professor at University of Michigan, and has also spent time at the Institute for Advanced Study in Princeton, N.J.; and at Fermi National Accelerator Laboratory’s Particle Astrophysics Center.

    Besides dark matter research, Zurek works on problems related to possible new physics at play in the infant universe and in the evolution of the universe’s structure, for example Her work often is at the intersection of particle physics experiments and astrophysics observations.

    Hard problems like the dark matter mystery are what drew her to physics at an early age, when she enrolled in college at the age of 15.

    “I wanted to understand how the universe worked. Plus, physics was hard and I liked that. I thought it was the hardest thing you could do, which I found very appealing. I decided at 15 that I wanted to make it a career, and I just never looked back,” she said.

    She knew, too, that she didn’t want to work directly on big science experiments. “I had always been fascinated about ideas: Ideas in philosophy, and the interplay between music and philosophy and physics.”

    She is a classical pianist with the ability to improvise melodies—she refers to this as a “tremendous intuition in how to make sounds”—and she still turns to music when confronting a physics problem. “When you’re really stuck on a problem you never stop thinking about it. Sometimes playing the piano helps.”

    When outdoors, Zurek enjoys sailing, hiking and alpine-style climbing—complete with ice axe and crampons—atop peaks such as Mount Rainer and Mount Shasta.

    As for the trail ahead in the dark matter hunt, Zurek said it’s important to be nimble and to expect the unexpected.

    “You don’t want to put yourself at a dead-end where you’re not exploring other possibilities,” she said.

    “The thing we don’t want to forget is: We don’t know what dark matter is. You have to have room for exploratory experiments, and you probably need a lot of them.”

    Learn more about Kathryn Zurek’s research: https://www.kzurek.theory.lbl.gov/.

    *Science paper:
    Echoes of a Hidden Valley at Hadron Colliders

    See the full article here .

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  • richardmitnick 3:58 pm on May 7, 2016 Permalink | Reply
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    From Ethan Siegel: “Ask Ethan: How Does Dark Matter Interact With Black Holes?” 

    Starts with a Bang

    May 7, 2016
    Ethan Siegel

    Black Hole Image credit NASA JPL-Caltech.
    Black Hole Image credit: NASA/JPL-Caltech

    Black holes are some of the most extreme objects in the Universe: a concentration of mass so great that it collapses, under General Relativity, into a singularity at its center. Atoms, nuclei, and even fundamental particles themselves are crushed down to an arbitrarily small thickness in our three-dimensional space. At the same time, everything that falls into it is doomed to never escape, but simply to add to its gravitational pull. What does that mean for dark matter? Our Patreon supporter kilobug wants to know:

    How does dark matter interact with black holes? Does it get sucked into the singularity like normal matter, contributing to the mass of the black hole? If so, when the black hole evaporates through Hawking radiation, what happens to [it]?

    This is a great question, and it all starts with what black holes actually are.

    Here on Earth, if you want to send something into space, you need to overcome the Earth’s gravitational pull. For our planet, what we call “escape velocity” is somewhere around 25,000 mph (or 11.2 km/s), which we can achieve with powerful rocket launches. If we were instead on the surface of the Sun, the escape velocity would be much greater: about 55 times as great, or 617.5 km/s. When our Sun dies, it will contract down to a white dwarf, of about 50% the Sun’s current mass but only the physical size of Earth. In this case, its escape velocity will be about 4570 km/s, or about 1.5% the speed of light.

    Sirius A and B, a normal (Sun-like) star and a white dwarf star. Even though the white dwarf is much lower in mass, its tiny, Earth-like size ensures its escape velocity is many times larger. Image credit: NASA, ESA and G. Bacon (STScI)

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    This is important, because as you concentrate more and more mass into a particular region of space, the speed required to escape this object gets closer and closer to the speed of light. And once your escape velocity at the object’s surface reaches or exceeds [?] the speed of light, it isn’t just that light can’t get out, it’s required that — at least as we understand matter, energy, space and time today — everything within that object collapse down to a singularity. The reason is simple: all the fundamental forces, including the forces that hold atoms, protons, or even quarks together, can move no faster than the speed of light. So if you’re at any point away from a central singularity and you’re trying to hold a more distant object up against gravitational collapse, you can’t do it; collapse is inevitable. And all you need to crest past this limit in the first place is a star more massive than about 20-40 times the mass of our Sun.

    Dying star. Associate Professor Orsola De Marco from Sydney’s Macquarie University.http://www.zmescience.com/space/dying-star-nebulae-26072011/

    When it runs out of fuel in its core, the center will implode under its own gravity, creating a catastrophic supernovae, blowing off and destroying the outer layers but leaving a black hole at the center. These “stellar mass” black holes, somewhere in the neighborhood of 10 solar masses, will grow over time, consuming any matter or energy that dares to venture too close to it. Even if you move at the speed of light when you fall in, you’ll never get out again. Due to the extreme curvature of space inside, you’ll inevitably encounter the singularity at the center. When that happens, all you do is add to the energy of the black hole.

    Black hole and its accretion disk. Image credit NASA Dana Berry SkyWorks Digital
    Black hole and its accretion disk. Image credit NASA Dana Berry SkyWorks Digital

    From the outside, we can’t tell whether a black hole was initially made up of protons and electrons, neutrons, dark matter or even antimatter. There are — as far as we can tell — only three properties that we can observe about a black hole from outside of it: its mass, its electric charge and its angular momentum, which is a measure of how fast it’s spinning. Dark matter, as far as we know, has no electric charge, nor does it have any of the other quantum numbers (color charge, baryon number, lepton number, lepton family number, etc.) that may or may not be conserved or destroyed as pertains to the black hole information paradox.

    Illustration credit: ESA, retrieved via http://chandra.harvard.edu/resources/illustrations/blackholes2.html.

    Because of how black holes are formed (from the explosions of supermassive stars), when they’re first formed, black holes are pretty much 100% normal (baryonic) matter, and just about 0% dark matter. Remember that dark matter interacts only gravitationally, unlike normal matter, which interacts via the gravitational, weak, electromagnetic and strong forces. Yes, there’s perhaps five times as much dark matter total in large galaxies and clusters as there is normal matter, but that’s summed up over the entire huge halo.

    Dark matter halo  Image credit: Virgo consortium / A. Amblard / ESA
    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

    In a typical galaxy, that dark matter halo extends for a few million light years, spherically, in all directions, while the normal matter is concentrated in a disk that’s just 0.01% the dark matter’s volume.

    Black holes tend to form in the innards of the galaxy, where the normal matter totally dominates over dark matter. Consider just the region of space where we’re located: around our Sun. If we drew a sphere that was 100 AU in radius (where one AU is the distance of the Earth from the Sun) around our Solar System, we’d enclose all the planets, moons, asteroids and pretty much the entire Kuiper belt…

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    … but the baryonic mass — the normal matter — of what would be inside our sphere would be dominated by our Sun, and would weigh about 2 × 10^30 kg. On the other hand, the total amount of dark matter in that same sphere? Only about 1 × 10^19 kg, or just 0.0000000005% the mass of the normal matter in that same region, or about the mass of a modest asteroid the size of Juno, approximately 200 km across.

    Our Solar system, NASA/Chandra
    Our Solar system, NASA/Chandra

    Over time, dark matter and normal matter both will collide with this black hole, getting absorbed and adding to its mass. The vast majority of black hole mass growth will come from normal matter and not dark matter, although at some point, many quadrillion years into the future, the rate of black hole decay will finally surpass the rate of black hole growth. The Hawking radiation process results in the emission of particles and photons from outside the black hole’s event horizon, conserving all the energy, charge and angular momentum from the black hole’s insides. This process may take anywhere from 10^67 years (for a solar mass black hole) to 10^100 years (for the most massive multi-billion solar mass black holes), but eventually what comes out is a mix of everything that’s possible.

    This means that some dark matter will come out of black holes, but that’s expected to be completely independent of whether a substantial amount of dark matter went into the black hole in the first place. All a black hole has memory of, once things have fallen in, is a small set of quantum numbers, and the amount of dark matter that went into it isn’t one of them. What comes out isn’t going to be the same as what you put in!

    Image credit: E. Siegel, on the quantum origin of Hawking Radiation.

    So at the end of the day, dark matter is just another food source for black holes, and not a very good one at that. Even worse: it’s not even an interesting source of food. What black hole “sees” is no different than shining a flashlight into a black hole and having your photons absorbed until, via E=mc^2, you’ve put in as much energy as there is mass in the dark matter that fell in. No other types of charge exist in dark matter, and other than the angular momentum from falling in off-center (which applies to photons, too), there’s no other effect on black holes at all, either going in or coming out.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 5:44 pm on May 2, 2016 Permalink | Reply
    Tags: , Dark Matter, ,   

    From Surf: “Notes from the underground – LUX celebrates 300 live days” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    Monday, May 2, 2016
    Constance Walter, Communications Director, SURF

    Amid streamers, a piñata and paper unicorns, LUX researchers celebrated the 300-live-day run of their dark matter detector.

    LUX Dark matter
    LUX Dark matter
    LUX Dark matter experiment
    Lux Dark Matter 2
    Lux Dark Matter 2

    “I would describe the mood as exciting, joyous and electric,” said Mark Hanhardt, Sanford Lab support scientist. Why unicorns? For LUX researchers, they symbolize thesearch for the elusive WIMP, or weakly interacting massive particle, the leading contender in the dark matter search.

    But don’t kid yourselves, in the search for dark matter, these researchers remain focused and motivated.

    LUX consists of one third-of-a-ton of liquid xenon inside a titanium vessel.

    Researchers hope to identify the very rare occasions when a dark matter particle collides with a xenon atom inside the detector. When that happens, the xenon atom will recoil and emit a tiny flash of light, which will be detected by sensitive light detectors.

    In October 2013, after a 90-live-day run, LUX announced it was the most sensitive dark matter detector in the world. “LUX was so much larger than existing detectors that within a few weeks of starting its first run in 2013, it had surpassed all previous direct detection experiments,” said Richard Gaitskell, co-spokesperson for LUX.
    And the trend continues. In December, LUX released a reanalysis of the 2013 data, which discussed new calibration techniques that allowed for even greater sensitivity. Those techniques, which included the use of tritiated methane, krypton-83 and a neutron generator, were used in the most recent run; however, results willnot be available before the end of 2016.

    The 300-day run began in November 2014 and the detector has been in WIMP search mode or calibration mode since. But it has not been without its challenges, Gaitskell said. “During any dark matter search, we must ensure the detector is taking data in a completely stable mode in which the operating conditions are clearly understood,” he said. “This means we monitor the detector health continually and occasionally we have to react to any apparent issues that have developed.”

    At regular intervals throughout the new run, calibrations were carried out for two weeks every four months to ensure a high level of accuracy in measuring responses to backgrounds and potential dark matter signals, he added.

    After 19 months, the run officially ended today at 1 p.m. “That’s a long time to to operate a detector without a significant break,” said Simon Fiorucci, LUX science operationsmanager. “But it was critical to demonstrate our ability to do so as we prepare to run LZ for more than three years.”

    Later this year, LUX will be decommissioned to make way for a new, much larger xenon detector, known as LUX-ZEPLIN, or LZ. This second generation dark matter detector will have a 10-ton liquid xenon target and be up to 100 times more sensitive.

    LUX Xenon experiment at SURF
    LUX Xenon experiment at SURF

    “The tremendous success of LUX paved the way for LZ,” said Murdock Gilchriese, LBNL (Lawrence Berkeley National Laboratory) operations manager for LUX and LZ project director. LZ will be located inside the same 72,000-gallon water tank that currently shields LUX.

    “Sanford Lab will continue to play a global role in the search for dark matter,” said Jaret Heise, science director at Sanford Lab. “We’re looking
    forward to working with the expanded collaboration, which will include 31 institutions and about 200 scientists.”

    In the meantime, LUX researchers are continuing their work, including testing several new calibration techniques that will be used in LZ. The team has come a long way and made significant progress. “We are all proud to have made it this far,” Fiorucci said.

    See the full article here .

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    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. 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

  • richardmitnick 9:54 am on April 23, 2016 Permalink | Reply
    Tags: , , Dark Matter,   

    From INVERSE: “What Killed the Dinosaurs?” 



    April 22, 2016
    Neel V. Patel

    Why does life on Earth take such a beating every 35 million years.

    Since life started on Earth, there have been five mass extinction events that have led to the obliteration of 99.9 percent of all the species that have ever lived. There are a lot of theories about the causes of those events, but the most compelling and —perhaps no coincidentally — widely accepted has long been that asteroids and other objects from space slammed into the planet, triggering a massive die-off. This is, most children are taught, how the dinosaurs died 65 million years ago.

    Scientists aren’t all satisfied by that explanation. Since asteroids tend to hit the planet in strange 35 million year cycles, a more massive object must be causing some sort of clockwork effect. Maybe it’s the mysterious elusive Planet X?

    Planet nine orbit image Credit Caltech R. Hurt (IPAC)
    Planet nine orbit image Credit Caltech R. Hurt (IPAC)

    Maybe a set of other strange-acting comets in unstable orbits? Or maybe it’s dark matter. Last year, astrophysicists Lisa Randall and Matthew Reece at Harvard University started pushing a credible if not popular theory that a dense cloud of dark matter sitting along the central plane of the Milky Way could be causing comets, asteroids, and other space objects to head our way on the regular.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al
    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al.

    Scientists think about 85 percent of the total matter in the universe is dark, which is pretty mind-boggling consider weve never detected the stuff. Still, there is reason to conclude that it exists because something has to account for the strange gravitational effects we witness in the movements and speeds of the Milky Way and other galaxies. Specifically, Randall and Reece believe a disk of dark matter stretching out a staggering 35 light-years thick is disturbing the trajectory of large asteroids and other objects and flinging them to the Earth. Their analysis of large impact craters on the surface of the planet — more than 12 miles wide, created in past 250 million years — indicates the likelihood these crashes were in some way influenced by the dark matter cycle is three times greater than the odds they are just random events.

    By itself, three-to-one odds aren’t statistically impressive. And, of course, while we kind of know dark matter is a thing, we don’t really know anything about dark matter. But the research itself is a sign that we are beginning to integrate more of what we know about astrophysical phenomena into the deep-time history of life (and death) on Earth. This is maybe the first time someone has linked the mystery of the dinosaurs extinction to the mystery of dark matter.

    One scientist, New York University geologist Michael R. Rampino, take this one step further and suggests that our own solar system actually moves through this cloud of dark matter periodically. Perhaps this movement doesn’t just knock asteroids into us, but it may heat up the planet and cause violent volcanic activity. For this to be true, a lot of other things have to happen. Among them, the dark matter disk has to be more dense than the galaxy’s highest concentration of stars. Also, the dark matter particles need to interact with Earth in such a way as to affect thermo-volcanic activity, but not completely melt the Earth’s core. It’s improbable but far from impossible.

    And that’s not even the weirdest theory that combines extinction and dark matter. Dayong Cao is a Beijing-based researcher who leads the Avoid Earth Extinction Association, an organization dedicated to highlighting and studying potential extraterrestrial threats to our planet (i.e. asteroids). He’s written several papers detailing his ideas on dark matter and asteroids.

    In short, Cao thinks asteroids moving through the dark matter clouds in the Milky Way are then infused with dark matter itself. These “dark asteroids or “dark comets” — which we can’t directly observe — slam into Earth, and bring dark matter to the planet itself. It’s only by studying the gravitational effects of these objects that we can predict if and when they will hit us. Caos theory kind of mashes the previously aforementioned ones into one, super-crazy annihilating idea.

    At this point, the only way to prove any of these theories is to find dark matter. There are detectors running all around the world, though the prevailing thought is that we need to prove dark matter indirectly by better studying its gravitational effect on other celestial objects. Whatever the methods, the day we can finally say weve discovered dark matter could be the day we kill two science birds with one dark-matter soaked stone.

    That is, if dark matter doesn’t manage to kill us off first.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

  • richardmitnick 1:48 pm on May 2, 2013 Permalink | Reply
    Tags: , Dark Matter, ,   

    From Fermilab: “New dark matter detector begins search for invisible particles” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    May 2, 2013
    Science contacts:
    Hugh Lippincott, Fermilab, 609-558-6313, hugh@fnal.gov .
    Juan Collar, University of Chicago, 773-702-4253, collar@uchicago.edu

    “Scientists this week heard their first pops in an experiment that searches for signs of dark matter in the form of tiny bubbles.

    This is an image of the first particle interactions seen in the COUPP-60 detector, located half a mile underground at SNOLAB in Ontario, Canada. Photo: SNOLAB

    Scientists will need further analysis to discern whether dark matter caused any of the COUPP-60 experiment’s first bubbles.

    ‘Our goal is to make the most sensitive detector to see signals of particles that we don’t understand,’ said Hugh Lippincott, a postdoc with the Department of Energy’s Fermi National Accelerator Laboratory who has spent much of the past several months leading the installation of the one-of-a-kind detector in a laboratory a mile and a half underground.

    COUPP-60 is a dark-matter experiment funded by DOE’s Office of Science. Fermilab managed the assembly and installation of the experiment’s detector.

    The COUPP-60 detector is a jar filled with purified water and CF3I—an ingredient found in fire extinguishers. The liquid in the detector is kept at a temperature and pressure slightly above the boiling point, but it requires an extra bit of energy to actually form a bubble. When a passing particle enters the detector and disturbs an atom in the clear liquid, it provides that energy.

    Dark-matter particles, which scientists think rarely interact with other matter, should form individual bubbles in the COUPP-60 tank.

    ‘The events are so rare, we’re looking for a couple of events per year,’ Lippincott said.”

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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