Tagged: Fritz Zwicky Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:53 am on February 23, 2020 Permalink | Reply
    Tags: , , , , , , , , , Fritz Zwicky, ,   

    From EarthSky: “What is dark matter?” 

    1

    From EarthSky

    February 23, 2020
    Andy Briggs

    Dark Matter doesn’t emit light. It can’t be directly observed with any of the existing tools of astronomers. Yet astrophysicists believe it and Dark Energy make up most of the mass of the cosmos. What dark matter is, and what it isn’t. here.

    1
    Since the 1930s, astrophysicists have been trying to explain why the visible material in galaxies can’t account for how galaxies are shaped, or how they behave. They believe a form of dark or invisible matter pervades our universe, but they still don’t know what this dark matter might be. Image via ScienceAlert.

    Dark matter is a mysterious substance thought to compose perhaps about 27% of the makeup of the universe. What is it? It’s a bit easier to say what it isn’t.

    It isn’t ordinary atoms – the building blocks of our own bodies and all we see around us – because atoms make up only somewhere around 5% of the universe, according to a cosmological model called the Lambda Cold Dark Matter Model (aka the Lambda-CDM model, or sometimes just the Standard Model).

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Dark Matter isn’t the same thing as Dark Energy, which makes up some 68% of the universe, according to the Standard Model.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Dark matter is invisible; it doesn’t emit, reflect or absorb light or any type of electromagnetic radiation such as X-rays or radio waves. Thus, dark matter is undetectable directly, as all of our observations of the universe, apart from the detection of gravitational waves, involve capturing electromagnetic radiation in our telescopes.

    Gravitational waves Werner Benger-ZIB-AEI-CCT-LSU

    Yet dark matter does interact with ordinary matter. It exhibits measurable gravitational effects on large structures in the universe such as galaxies and galaxy clusters. Because of this, astronomers are able to make maps of the distribution of dark matter in the universe, even though they cannot see it directly.

    They do this by measuring the effect dark matter has on ordinary matter, through gravity.

    2
    This all-sky image – released in 2013 – shows the distribution of dark matter across the entire history of the universe as seen projected on the sky. It’s based on data collected with the European Space Agency’s Planck satellite.

    ESA/Planck 2009 to 2013

    Dark blue areas represent regions that are denser than their surroundings. Bright areas represent less dense regions. The gray portions of the image correspond to patches of the sky where foreground emission, mainly from the Milky Way but also from nearby galaxies, prevents cosmologists from seeing clearly. Image via ESA.

    There is currently a huge international effort to identify the nature of dark matter. Bringing an armory of advanced technology to bear on the problem, astronomers have designed ever-more complex and sensitive detectors to tease out the identity of this mysterious substance.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

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

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Dark matter might consist of an as yet unidentified subatomic particle of a type completely different from what scientists call baryonic matter – that’s just ordinary matter, the stuff we see all around us – which is made of ordinary atoms built of protons and neutrons.

    The list of candidate subatomic particles breaks down into a few groups: there are the WIMPs (Weakly Interacting Massive Particles), a class of particles thought to have been produced in the early universe. Astronomers believe that WIMPs might self-annihilate when colliding with each other, so they have searched the skies for telltale traces of events such as the release of neutrinos or gamma rays. So far, they’ve found nothing. In addition, although a theory called supersymmetry predicts the existence of particles with the same properties as WIMPs, repeated searches to find the particles directly have also found nothing, and experiments at the Large Hadron Collider to detect the expected presence of supersymmetry have completely failed to find it.

    Standard Model of Supersymmetry via DESY

    CERN/LHC Map


    CERN LHC Maximilien Brice and Julien Marius Ordan


    SixTRack CERN LHC particles

    Several different types of detector have been used to detect WIMPs. The general idea is that very occasionally, a WIMP might collide with an ordinary atom and release a faint flash of light, which can be detected. The most sensitive detector built to date is XENON1T, which consists of a 10-meter cylinder containing 3.2 tons of liquid xenon, surrounded by photomultipliers to detect and amplify the incredibly faint flashes from these rare interactions. As of July 2019, when the detector was decommissioned to pave the way for a more sensitive instrument, the XENONnT, no collisions between WIMPs and the xenon atoms had been seen.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy


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

    At the moment, a hypothetical particle called the Axion is receiving much attention.

    CERN CAST Axion Solar Telescope

    As well as being a strong candidate for dark matter, the existence of axions is also thought to provide the answers to a few other persistent questions in physics such as the Strong CP Problem.

    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Some astronomers have tried to negate the need the existence of dark matter altogether by postulating something called Modified Newtonian dynamics (MOND).

    Mordehai Milgrom, MOND theorist, is an Israeli physicist and professor in the department of Condensed Matter Physics at the Weizmann Institute in Rehovot, Israel http://cosmos.nautil.us

    MOND Modified Newtonian Dynamics a Humble Introduction Marcus Nielbock

    The idea behind this is that gravity behaves differently over long distances to what it does locally, and this difference of behavior explains phenomena such as galaxy rotation curves which we attribute to dark matter. Although MOND has its supporters, while it can account for the rotation curve of an individual galaxy, current versions of MOND simply cannot account for the behavior and movement of matter in large structures such as galaxy clusters and, in its current form, is thought unable to completely account for the existence of dark matter. That is to say, gravity does behave in the same way at all scales of distance. Most versions of MOND, on the other hand, have two versions of gravity, the weaker one occurring in regions of low mass concentration such as in the outskirts of galaxies. However, it is not inconceivable that some new version of MOND in the future might yet account for dark matter.

    Although some astronomers believe we will establish the nature of dark matter in the near future, the search so far has proved fruitless, and we know that the universe often springs surprises on us so that nothing can be taken for granted.

    The approach astronomers are taking is to eliminate those particles which cannot be dark matter, in the hope we will be left with the one which is.

    It remains to be seen if this approach is the correct one.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 1:54 pm on February 11, 2020 Permalink | Reply
    Tags: Although scientists have yet to find the spooky stuff they aren’t completely in the dark., , , Fritz Zwicky, It all adds up to 85% of the universe., It shaped entire galaxies without touching a thing., It’s built to last., Natalia Toro, ,   

    From Symmetry: “What we know about dark matter” 

    Symmetry Mag
    From Symmetry<

    02/11/20
    Jim Daley

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Although scientists have yet to find the spooky stuff, they aren’t completely in the dark.

    There are a lot of things scientists don’t know about dark matter: Can we catch it in a detector? Can we make it in a lab? What kinds of particles is it made of? Is it made of more than one kind of particle? Is it even made of particles at all?

    In short, dark matter is still pretty mysterious. The term is really just the name scientists gave to an ingredient that seems to be missing from our understanding of the universe.

    But there are some things scientists can definitively say about the stuff.

    Natalia Toro is a theoretical physicist at the US Department of Energy’s SLAC National Accelerator Laboratory and a member of the Light Dark Matter Experiment (LDMX) and the Beam Dump Experiment (BDX) dark matter search. She gave a talk at the 2019 meeting of the American Physical Society’s Division of Particles and Fields about the short list of things we do know about dark matter.

    2
    Light Dark Matter Experiment (LDMX).https://www.researchgate.net/figure/The-LDMX-experiment-layout_fig4_330726206

    3
    Beam Dump Experiment. https://www.jlab.org/accel/ops/ops_liaison/BDX/BDX.html

    1. It’s built to last.

    Dark matter formed very early on in the universe’s history. The evidence of this is apparent in the cosmic microwave background, or CMB—the ethereal layer of radiation left over from the universe’s searingly hot first moments.

    The fact that so much dark matter still seems to be around some 13.7 billion years later tells us right away that it has a lifetime of at least 1017 seconds (or about 3 billion years), Toro says.

    But there is another, more obvious clue that the lifetime of dark matter is much longer than that: We don’t see any evidence of dark matter decay.

    The heaviest particles in the Standard Model of particle physics break down, releasing their energy in the form of lighter particles. Dark matter doesn’t seem to do that, Toro says. “Whatever dark matter is made of, it lasts a really long time.”

    This property isn’t unheard of—electrons, protons and neutrinos all have extremely long lifespans—but it would be unusual, especially if dark matter turns out to be heavier than those light, stable particles.

    “One possibility is that there’s some kind of charge in nature, and dark matter is the lightest thing that carries that charge,” Toro says.

    In particle physics, charge must be conserved—meaning it cannot be created or destroyed. Take the decay of a muon, a heavier version of an electron. A muon often decays into a pair of neutrinos, one positively charged and one negatively charged, and an electron, which shares the muon’s negative charge. The charges of the neutrinos cancel one another out. So even though the muon has fallen apart into three other particles, its electromagnetic charge is conserved overall in the results of the decay.

    The electron is the lightest particle with a negative electromagnetic charge. Since there’s nothing with a smaller mass for it to decay into, it remains stable.

    But the electromagnetic charge is not the only type of charge. Protons, for example, are the lightest particle to carry a charge called the baryon number, which is related to the fact that they’re made of particles called quarks (but not anti-quarks). Quarks and gluons have what physicists call color charge, which seems to be conserved in particle interactions.

    It could be that dark matter particles are the most stable particles with a new kind of charge.

    2. It shaped entire galaxies without touching a thing.

    Dark matter’s apparent stability seems to have been key to another of its qualities: its ability to influence the evolution of the universe. Astrophysicists think that most galaxies would probably not have formed as they did without the help of dark matter.

    In the 1930s Swiss astrophysicist Fritz Zwicky noted that something seemed to be causing galaxies in the Coma Cluster to behave as if they were 400 times heavier than they would if they contained only luminous material. That discrepancy has today been calculated to be smaller, but it still exists. Zwicky coined the term “dark matter” to describe whatever could be giving the galaxies their extra mass.

    In the 1970s Vera Rubin, an astronomer at the Carnegie Institution in Washington, used spectrographic evidence to determine that spiral galaxies such as our own also seemed to be acting more massive than they appeared. They were rotating far more quickly than expected, something that could happen if they were, for example, sitting in invisible halos of dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

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

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Scientists have seen another effect of dark matter on luminous material. Clusters of dark matter act as cosmic potholes on the path that light travels through the cosmos, bending and distorting it in a process called “gravitational lensing.” Astronomers can map the distribution of otherwise invisible dark matter by studying this lensing.

    Just like regular matter, dark matter isn’t evenly distributed across the universe. Astrophysicists think that when the galaxies first formed, areas of the universe that had slightly more dark matter (and thus more gravitational pull) attracted more matter, leading to the distribution of galaxies that we now see.

    Had there been a different pattern of dark matter throughout the universe—or slightly more or less of it—then galaxies might have formed later, formed with different densities or never formed at all, Toro says. “Galaxies become a lot denser, and you could end up in a situation where lots of black holes form, or you could end up with much more dark matter.”

    Despite being massively (forgive the pun) influential, dark matter is famously standoffish, avoiding most of the kinds of interactions that Standard Model particles commonly undergo from the very beginning. “One thing that we know concretely from looking at the CMB is that there was a component of that plasma that was not interacting with the electrons and protons,” she says. “That’s one very clear constraint—that the constituents of dark matter interacted less than electrons and protons.”

    Dark matter is so nonreactive that it may not even interact with itself; when two galaxies merge, their respective dark matter halos simply pass through one another like ghosts.

    3. It all adds up to 85%.

    Amazingly, despite being unclear on precisely what dark matter is, astrophysicists do know pretty well how much of it there is—which is why we can say that it accounts for 85% of the known matter in the universe. Physicists call that amount the “cosmological abundance” of dark matter.

    Cosmological abundance can tell us a great deal about the makeup of the universe, Toro says—particularly in its earliest days, when it was much smaller and denser. During the evolution of the early universe, “average density was very representative” of the actual dark matter present in any area of it, she says.

    Currently, Toro says, dark matter’s cosmological abundance is “the only number physicists can hang our hat on.” Scientists have proposed—and are actively searching for—a number of different possible dark matter candidates. Whether dark matter is made up of a smaller number of heavy WIMPs or a larger number of light axions, its total mass must add up to the measure of the cosmological abundance.

    Toro says it’s important to take that number as far as it can be taken and to try to extrapolate different strategies for looking for dark matter from it.

    Quantifying anything else about dark matter—its interaction strength, its scattering rate and a laundry list of other potential properties—would be “amazing,” she says. “Having any confirmation, finding one more property of dark matter that we could actually quantify, would be a huge jump.”

    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.


     
  • richardmitnick 2:24 pm on January 16, 2020 Permalink | Reply
    Tags: , , , , , Fritz Zwicky, , The LSST Vera C. Rubin Observatory,   

    From The Kavli Foundation: “Behold the Whole Sky” The LSST Vera C. Rubin Observatory 

    KavliFoundation

    From The Kavli Foundation

    01/02/2020
    Adam Hadhazy

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

    The LSST Vera C. Rubin Observatory

    LSST Camera, built at SLAC



    LSST telescope, Vera C. Rubin Observatory, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    When construction is complete, the LSST, Vera C. Rubin Observatory, will be “the widest, fastest, deepest eye of the new digital age.”

    There’s about to be a new telescope in town—in the figurative sense, that is, unless you happen to literally live more than a mile-and-a-half up on the summit of a mountain named Cerro Pachón in the foothills of the Chilean Andes.

    There, construction is humming along for the Large Synoptic Survey Telescope, or LSST. Slated to start science operations early next decade, LSST in all likelihood will be a gamechanger for astronomy and astrophysics.

    What makes LSST so special is how big and fast it will be compared to other telescopes. “Big” in this case refers to the telescope’s field of view, which captures a chunk of sky 40 times the size of the full Moon. “Big” also refers to LSST’s mirror size, a very respectable 8.4 meters in diameter, which means it can collect ample amounts of cosmic light. Thirdly, “big” applies to LSST’s 3.2 billion-pixel camera, the biggest digital camera ever built. Put all those bits together, and LSST will be able to record images of significantly fainter and farther-away objects than other ground-based optical telescopes.

    And finally, as for “fast,” LSST will soak up more than 800 panoramas each night, cumulatively scanning the entire sky twice per week. That means the telescope will catch sight of fleeting astrophysical events, known as transients, that are often missed because telescopes—even today’s state-of-the-art, automated networks of ‘scopes—are not gobbling up so much of the sky so quickly. Transients that last days, weeks, and months—for instance, cataclysmic stellar explosions called supernovae—are routinely spotted. But the shortest events, lasting mere hours or even minutes, are another, untold story.

    “Unfortunately, we still know relatively little about the transient optical sky because we have never before had a survey that can make observations of a very large fraction of the sky repeatedly every few nights,” says Steven Kahn, Director of the LSST project. “LSST will meet this need.”

    Kahn, the Cassius Lamb Kirk Professor in the Natural Sciences and Professor of Particle Physics and Astrophysics at Stanford University, is also a member of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). He stepped into the director role back in 2013 when LSST was on the drawing board. Now the huge instrument is nearing the completion of its construction. Kahn and his colleagues are dearly looking forward to all that LSST will bring to the table, building on the pioneering work into gauging the transient sky underway with other, precursor projects worldwide.

    “LSST will go significantly deeper and cover the sky more rapidly,” says Kahn. “By covering more sky per unit time, we are more sensitive to very rare events, which are often the most interesting.”

    In this way, LSST is going to open up a major discovery space, for phenomena both (poorly) known and (entirely) unknown.

    “The Universe is far from static,” says Kahn. “There are stellar explosions of many different kinds that allow stars to brighten dramatically and then fade away on different timescales.” Some of these transient flashes of light are expected from the vicinities of neutron stars and black holes as they interact with matter that strays too close. Researchers hope to gain new insights into these dense objects’ properties, whose extreme physics challenge our best-supported theories.

    Another primary goal for LSST is to advance our understanding of the “dark universe” of dark matter and dark energy. Together, these entities compose 95 percent of the cosmos, with the “normal” matter that makes up stars, planets, and people registering as the remaining rounding error. Yet scientists have only stabs in the dark, as it were, on what exactly dark matter and dark energy really are. LSST will help by acquiring images of billions of galaxies, stretching back to some of the earliest epochs in the universe. Analyzing the shapes and distributions of these galaxies in space as well as time (recall that the farther away you see something in the universe, the farther you’re seeing back in time) will better show dark matter’s role in building up cosmic structure. The signature of dark energy, a force that is seemingly accelerating the universe’s expansion, will also be writ across the observed eons of galactic loci.

    Closer to home, LSST will vastly expand our knowledge of our own Solar System. It will take a census of small bodies, such as asteroids and comets, that fly by overhead, too faint for us humans to notice but there all the same—and in rare instances, potentially dangerously so; just ask the dinosaurs.

    “LSST will measure everything that moves in the sky,” says Kahn. “Of particular interest, we will provide the most complete catalogue of potentially hazardous asteroids, those objects whose orbits might allow them to impact the Earth.”

    Not done yet, LSST will also extend our catalogue of stars in the galaxy, aiding in charting the history and evolution of our own Milky Way galaxy. Furthermore, LSST will be a premier instrument for discovering the sources of gravitational waves, the ripples in spacetime first predicted by Albert Einstein in 1915 and finally directly detected in 2015 by the LIGO experiment. It can be a tough business today, even with the rich array of telescopes in operation, to rapidly pinpoint the visible light that gravitational wave-spawning neutron star collisions give off. LSST should aid in that regard admirably.

    The wait is nearly over. The LSST building is nearly complete, the large mirrors are on site, and the camera is being integrated at the at SLAC National Accelerator Laboratory in California, which co-hosts KIPAC along with Stanford.

    “Basically, everything that needed to be fabricated for the LSST telescope and camera has been fabricated,” says Kahn. “The remaining work largely involves putting the system together and getting it working.”

    Kahn has been to the telescope site recently, in both September and October. He likes what he sees.

    “Visiting the site in Chile is a remarkable experience,” Kahn says. “It is a beautiful site, and the LSST facility sits prominently atop the edge of a cliff on Cerro Pachón. The sheer size of the building and its complexity is striking.”

    Before long, the impressiveness of the building will recede into the background as the profundity of the science LSST generates takes center stage.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

     
  • richardmitnick 10:17 am on December 29, 2019 Permalink | Reply
    Tags: , , , , Fritz Zwicky, , , ,   

    From particlebites: “Dark Photons in Light Places” 

    particlebites bloc

    From particlebites

    December 29, 2019
    Amara McCune

    Title: “Searching for dark photon dark matter in LIGO O1 data”

    Author: Huai-Ke Guo, Keith Riles, Feng-Wei Yang, & Yue Zhao

    Reference: https://www.nature.com/articles/s42005-019-0255-0

    There is very little we know about dark matter save for its existence.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB] hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    CMB per ESA/Planck

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

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Its mass(es), its interactions, even the proposition that it consists of particles at all is mostly up to the creativity of the theorist. For those who don’t turn to modified theories of gravity to explain the gravitational effects on galaxy rotation and clustering that suggest a massive concentration of unseen matter in the universe (among other compelling evidence), there are a few more widely accepted explanations for what dark matter might be. These include weakly-interacting massive particles (WIMPS), primordial black holes, or new particles altogether, such as axions or dark photons.

    In particle physics, this latter category is what’s known as the “hidden sector,” a hypothetical collection of quantum fields and their corresponding particles that are utilized in theorists’ toolboxes to help explain phenomena such as dark matter. In order to test the validity of the hidden sector, several experimental techniques have been concocted to narrow down the vast parameter space of possibilities, which generally consist of three strategies:

    1.Direct detection: Detector experiments look for low-energy recoils of dark matter particle collisions with nuclei, often involving emitted light or phonons.
    2.Indirect detection: These searches focus on potential decay products of dark matter particles, which depends on the theory in question.
    3.Collider production: As the name implies, colliders seek to produce dark matter in order to study its properties. This is reliant on the other two methods for verification.

    The first detection of gravitational waves from a black hole merger in 2015 ushered in a new era of physics, in which the cosmological range of theory-testing is no longer limited to the electromagnetic spectrum.

    MIT /Caltech Advanced aLigo


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Caltech/MIT Advanced aLigo detector installation Hanford, WA, USA

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/NASA eLISA space based, the future of gravitational wave research

    Bringing LIGO (the Laser Interferometer Gravitational-Wave Observatory) to the table, proposals for the indirect detection of dark matter via gravitational waves began to spring up in the literature, with implications for primordial black hole detection or dark matter ensconced in neutron stars. Yet a new proposal, in a paper by Guo et. al., [Scientific Reports-Communication Physics] suggests that direct dark matter detection with gravitational waves may be possible, specifically in the case of dark photons.

    Dark photons are hidden sector particles in the ultralight regime of dark matter candidates. Theorized as the gauge boson of a U(1) gauge group, meaning the particle is a force-carrier akin to the photon of quantum electrodynamics, dark photons either do not couple or very weakly couple to Standard Model particles in various formulations. Unlike a regular photon, dark photons can acquire a mass via the Higgs mechanism. Since dark photons need to be non-relativistic in order to meet cosmological dark matter constraints, we can model them as a coherently oscillating background field: a plane wave with amplitude determined by dark matter energy density and oscillation frequency determined by mass. In the case that dark photons weakly interact with ordinary matter, this means an oscillating force is imparted. This sets LIGO up as a means of direct detection due to the mirror displacement dark photons could induce in LIGO detectors.

    3
    Figure 1: The experimental setup of the Advanced LIGO interferometer. We can see that light leaves the laser and is reflected between a few power recycling mirrors (PR), split by a beam splitter (BS), and bounced between input and end test masses (ITM and ETM). The entire system is mounted on seismically-isolated platforms to reduce noise as much as possible. Source: https://arxiv.org/pdf/1411.4547.pdf

    LIGO consists of a Michelson interferometer, in which a laser shines upon a beam splitter which in turn creates two perpendicular beams. The light from each beam then hits a mirror, is reflected back, and the two beams combine, producing an interference pattern. In the actual LIGO detectors, the beams are reflected back some 280 times (down a 4 km arm length) and are split to be initially out of phase so that the photodiode detector should not detect any light in the absence of a gravitational wave. A key feature of gravitational waves is their polarization, which stretches spacetime in one direction and compresses it in the perpendicular direction in an alternating fashion. This means that when a gravitational wave passes through the detector, the effective length of one of the interferometer arms is reduced while the other is increased, and the photodiode will detect an interference pattern as a result.

    LIGO has been able to reach an incredible sensitivity of one part in 10^{23} in its detectors over a 100 Hz bandwidth, meaning that its instruments can detect mirror displacements up to 1/10,000th the size of a proton. Taking advantage of this number, Guo et. al. demonstrated that the differential strain (the ratio of the relative displacement of the mirrors to the interferometer’s arm length, or h = \Delta L/L) is also sensitive to ultralight dark matter via the modeling process described above. The acceleration induced by the dark photon dark matter on the LIGO mirrors is ultimately proportional to the dark electric field and charge-to-mass ratio of the mirrors themselves.

    Once this signal is approximated, next comes the task of estimating the background. Since the coherence length is of order 10^9 m for a dark photon field oscillating at order 100 Hz, a distance much larger than the separation between the LIGO detectors at Hanford and Livingston (in Washington and Louisiana, respectively), the signals from dark photons at both detectors should be highly correlated. This has the effect of reducing the noise in the overall signal, since the noise in each of the detectors should be statistically independent. The signal-to-noise ratio can then be computed directly using discrete Fourier transforms from segments of data along the total observation time. However, this process of breaking up the data, known as “binning,” means that some signal power is lost and must be corrected for.

    4
    Figure 2: The end result of the Guo et. al. analysis of dark photon-induced mirror displacement in LIGO. Above we can see a plot of the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. We can see that over further Advanced LIGO runs, up to O4-O5, these limits are expected to improve by several orders of magnitude. Source: https://www.nature.com/articles/s42005-019-0255-0

    In applying this analysis to the strain data from the first run of Advanced LIGO, Guo et. al. generated a plot which sets new limits for the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. There are a few key subtleties in this analysis, primarily that there are many potential dark photon models which rely on different gauge groups, yet this framework allows for similar analysis of other dark photon models. With plans for future iterations of gravitational wave detectors, further improved sensitivities, and many more data runs, there seems to be great potential to apply LIGO to direct dark matter detection. It’s exciting to see these instruments in action for discoveries that were not in mind when LIGO was first designed, and I’m looking forward to seeing what we can come up with next!

    Learn More:

    An overview of gravitational waves and dark matter: https://www.symmetrymagazine.org/article/what-gravitational-waves-can-say-about-dark-matter
    A summary of dark photon experiments and results: https://physics.aps.org/articles/v7/115
    Details on the hardware of Advanced LIGO: https://arxiv.org/pdf/1411.4547.pdf
    A similar analysis done by Pierce et. al.: https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.121.061102

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    What is ParticleBites?

    ParticleBites is an online particle physics journal club written by graduate students and postdocs. Each post presents an interesting paper in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

    The papers are accessible on the arXiv preprint server. Most of our posts are based on papers from hep-ph (high energy phenomenology) and hep-ex (high energy experiment).

    Why read ParticleBites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

    Our goal is to solve this problem, one paper at a time. With each brief ParticleBite, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in particle physics.

    Who writes ParticleBites?

    ParticleBites is written and edited by graduate students and postdocs working in high energy physics. Feel free to contact us if you’re interested in applying to write for ParticleBites.

    ParticleBites was founded in 2013 by Flip Tanedo following the Communicating Science (ComSciCon) 2013 workshop.

    2
    Flip Tanedo UCI Chancellor’s ADVANCE postdoctoral scholar in theoretical physics. As of July 2016, I will be an assistant professor of physics at the University of California, Riverside

    It is now organized and directed by Flip and Julia Gonski, with ongoing guidance from Nathan Sanders.

     
  • richardmitnick 11:41 am on April 18, 2019 Permalink | Reply
    Tags: "What gravitational waves can say about dark matter", , , , , , , , Fritz Zwicky, ,   

    From Symmetry: “What gravitational waves can say about dark matter” 

    Symmetry Mag
    From Symmetry

    04/18/19
    Caitlyn Buongiorno

    Scientists think that, under some circumstances, dark matter could generate powerful enough gravitational waves for equipment like LIGO to detect.

    1
    Artwork by Sandbox Studio, Chicago

    In 1916, Albert Einstein published his theory of general relativity, which established the modern view of gravity as a warping of the fabric of spacetime. The theory predicted that objects that interact with gravity could disturb that fabric, sending ripples across it.

    Any object that interacts with gravity can create gravitational waves. But only the most catastrophic cosmic events make gravitational waves powerful enough for us to detect. Now that observatories have begun to record gravitational waves on a regular basis, scientists are discussing how dark matter—only known so far to interact with other matter only through gravity—might create gravitational waves strong enough to be found.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster. But , Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The spacetime blanket

    In the universe, space and time are invariably linked as four-dimensional spacetime. For simplicity, you can think of spacetime as a blanket suspended above the ground.

    Spacetime with Gravity Probe B. NASA

    Jupiter might be a single Cheerio on top of that blanket. The sun could be a tennis ball. R136a1—the most massive known star—might be a 40-pound medicine ball.

    Each of these objects weighs down the blanket where it sits: the heavier the object, the bigger the dip in the blanket. Like objects of different weights on a blanket, objects of different masses have different effects on the fabric of spacetime. A dip in spacetime is gravitational field.

    The gravitational field of one object can affect another object. The other object might fall into the first object’s gravitational field and orbit around it, like the moon around Earth, or Earth around the sun.

    Alternatively, two bodies with gravitational fields might spiral toward each other, getting closer and closer until they collide. As this happens, they create ripples in spacetime—gravitational waves.

    On September 14, 2015, scientists used the Laser Interferometer Gravitational-Wave Observatory, or LIGO, to make the first direct observation of gravitational waves, part of the buildup to the crash between two massive black holes.

    Since that first detection, the LIGO collaboration—together with the collaboration that runs a partner gravitational-wave observatory called Virgo—has detected gravitational waves from at least 10 more mergers of black holes and, in 2017, the first merger between two neutron stars.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Dark matter is believed to be five times as prevalent as visible matter. Its gravitational effects are seen throughout the universe. Scientists think they have yet to definitively see gravitational waves caused by dark matter, but they can think of numerous ways this might happen.

    Primordial black holes

    Scientists have seen the gravitational effects of dark matter, so they know it must be there—or at least, something must be going on to cause those effects. But so far, they’ve never directly detected a dark matter particle, so they’re not sure exactly what dark matter is like.

    One idea is that some of the dark matter could actually be primordial black holes.

    Imagine the universe as an infinitely large petri dish. In this scenario, the Big Bang is the point where matter-bacteria begins to grow. That point quickly expands, moving outward to encompass more and more of the petri dish. If that growth is slightly uneven, certain areas will become more densely inhabited by matter than others.

    These pockets of dense matter—mostly photons at this point in the universe—might have collapsed under their own gravity and formed early black holes.

    “I think it’s an interesting theory, as interesting as a new kind of particle,” says Yacine Ali-Haimoud, an assistant professor of physics at New York University. “If primordial black holes do exist, it would have profound implications on the conditions in the very early universe.”

    By using gravitational waves to learn about the properties of black holes, LIGO might be able to prove or constrain this dark matter theory.

    Unlike normal black holes, primordial black holes don’t have a minimum mass threshold they need to reach in order to form. If LIGO were to see a black hole less massive than the sun, for example, it might be a primordial black hole.

    Even if primordial black holes do exist, it’s doubtful that they account for all of the dark matter in the universe. Still, finding proof of primordial black holes would expand our fundamental understanding of dark matter and how the universe began.

    Neutron star rattles

    Dark matter seems to interact with normal matter only through gravity, but, based on the way known particles interact, theorists think it’s possible that dark matter might also interact with itself.

    If that is the case, dark matter particles might bind together to form dark objects that are as compact as a neutron star.

    We know that stars drastically “weigh down” the fabric of spacetime around them. If the universe were populated with compact dark objects, there would be a chance that at least some of them would end up trapped inside of ordinary matter stars.

    A normal star and a dark object would interact only through gravity, allowing the two to co-exist without much of a fuss. But any disruption to the star—for example, a supernova explosion—could create a rattle-like disturbance between the resulting neutron star and the trapped dark object. If such an event occurred in our galaxy, it would create detectable gravitational waves

    “We understand neutron stars quite well,” says Sanjay Reddy, University of Washington physics professor and senior fellow with the Institute for Nuclear Theory. “If something ‘odd’ happens with gravitational waves, we would know there was potentially something new going on that might involve dark matter.”

    The likelihood that any exist in our solar system is limited. Chuck Horowitz, Maria Alessandra Papa and Reddy recently analyzed LIGO’s data and found no indication of compact dark objects of a specific mass range within Earth, Jupiter or the sun.

    Further gravitational-wave studies could place further constraints on compact dark objects. “Constraints are important,” says Ann Nelson, a physics professor at the University of Washington. “They allow us to improve existing theories and even formulate new ones.”

    Axion stars

    One light dark matter candidate is the axion, named by physicist Frank Wilczek after a brand of detergent, in reference to its ability to tidy up a problem in the theory of quantum chromodynamics.

    Scientists think it could be possible for axions to bind together into axion stars, similar to neutron stars but made up of extremely compact axion matter.

    “If axions exist, there are scenarios where they can cluster together and form stellar objects, like ordinary matter,” says Tim Dietrich, a LIGO-Virgo member and physicist. “We don’t know if axion stars exist, and we won’t know for sure until we find constraints for our models.”

    If an axion star merged with a neutron star, scientists might not be able to tell the difference between the two with their current instruments. Instead, scientists would need to rely on electromagnetic signals accompanying the gravitational wave to identify the anomaly.

    It’s also possible that axions could bunch around a binary black hole or neutron star system. If those stars then merged, the changes in the axion “cloud” would be visible in the gravitational wave signal. A third possibility is that axions could be created by the merger, an action that would be reflected in the signal.

    This month, the LIGO-Virgo collaborations began their third observing run and, with new upgrades, expect to detect a merger event every week.

    Gravitational-wave detectors have already proven their worth in confirming Einstein’s century-old prediction. But there is still plenty that studying gravitational waves can teach us. “Gravitational waves are like a completely new sense for science,” Ali-Haimoud says. “A new sense means new ways to look at all the big questions in physics.”

    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.


     
  • richardmitnick 11:00 am on November 29, 2018 Permalink | Reply
    Tags: , , , , , , Fritz Zwicky, ,   

    From NASA/ESA Hubble Telescope: “Hubble Uncovers Thousands of Globular Star Clusters Scattered Among Galaxies” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    From NASA/ESA Hubble Telescope

    Nov 29, 2018

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    Juan Madrid
    Australian Telescope National Facility, Sydney, Australia
    jmadrid@astro.swin.edu.au

    1
    Survey will allow for mapping of dark matter in huge galaxy cluster

    Gazing across 300 million light-years into a monstrous city of galaxies, astronomers have used NASA’s Hubble Space Telescope to do a comprehensive census of some of its most diminutive members: a whopping 22,426 globular star clusters found to date.

    The survey, published in the November 9, 2018, issue of The Astrophysical Journal, will allow for astronomers to use the globular cluster field to map the distribution of matter and dark matter in the Coma galaxy cluster, which holds over 1,000 galaxies that are packed together.

    Because globular clusters are much smaller than entire galaxies – and much more abundant – they are a much better tracer of how the fabric of space is distorted by the Coma cluster’s gravity. In fact, the Coma cluster is one of the first places where observed gravitational anomalies were considered to be indicative of a lot of unseen mass in the universe – later to be called “dark matter.”

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    Among the earliest homesteaders of the universe, globular star clusters are snow-globe-shaped islands of several hundred thousand ancient stars. They are integral to the birth and growth of a galaxy. About 150 globular clusters zip around our Milky Way galaxy, and, because they contain the oldest known stars in the universe, were present in the early formative years of our galaxy.

    Some of the Milky Way’s globular clusters are visible to the naked eye as fuzzy-looking “stars.” But at the distance of the Coma cluster, its globulars appear as dots of light even to Hubble’s super-sharp vision. The survey found the globular clusters scattered in the space between the galaxies. They have been orphaned from their home galaxy due to galaxy near-collisions inside the traffic-jammed cluster. Hubble revealed that some globular clusters line up along bridge-like patterns. This is telltale evidence for interactions between galaxies where they gravitationally tug on each other like pulling taffy.

    Astronomer Juan Madrid of the Australian Telescope National Facility in Sydney, Australia first thought about the distribution of globular clusters in Coma when he was examining Hubble images that show the globular clusters extending all the way to the edge of any given photograph of galaxies in the Coma cluster.

    He was looking forward to more data from one of the legacy surveys of Hubble that was designed to obtain data of the entire Coma cluster, called the Coma Cluster Treasury Survey. However, halfway through the program, in 2006, Hubble’s powerful Advanced Camera for Surveys (ACS) had an electronics failure. (The ACS was later repaired by astronauts during a 2009 Hubble servicing mission.)

    NASA Hubble Advanced Camera forSurveys

    To fill in the survey gaps, Madrid and his team painstakingly pulled numerous Hubble images of the galaxy cluster taken from different Hubble observing programs. These are stored in the Space Telescope Science Institute’s Mikulski Archive for Space Telescopes in Baltimore, Maryland. He assembled a mosaic of the central region of the cluster, working with students from the National Science Foundation’s Research Experience for Undergraduates program. “This program gives an opportunity to students enrolled in universities with little or no astronomy to gain experience in the field,” Madrid said.

    The team developed algorithms to sift through the Coma mosaic images that contain at least 100,000 potential sources. The program used globular clusters’ color (dominated by the glow of aging red stars) and spherical shape to eliminate extraneous objects – mostly background galaxies unassociated with the Coma cluster.

    Though Hubble has superb detectors with unmatched sensitivity and resolution, their main drawback is that they have tiny fields of view. “One of the cool aspects of our research is that it showcases the amazing science that will be possible with NASA’s planned Wide Field Infrared Survey Telescope (WFIRST) that will have a much larger field of view than Hubble,” said Madrid.

    NASA/WFIRST

    “We will be able to image entire galaxy clusters at once.”

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    ESA50 Logo large

    AURA Icon

     
  • richardmitnick 10:43 am on November 14, 2018 Permalink | Reply
    Tags: , Fritz Zwicky, , , , The search for Dark Matter, ,   

    From Sanford Underground Research Facility: “Success of experiment requires testing” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    November 13, 2018
    Erin Broberg

    1
    Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC), works on the mock PMT [photomultiplier tubes] array. Erin Broberg

    “The LZ detector is kind of like a spacecraft,” said Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC). “Repairing it after it’s installed would be very difficult, so we do everything we can to make sure it works correctly the first time.”

    LZ Dark Matter Experiment at SURF lab

    LBNL LZ project at SURF, Lead, SD, USA

    Biesiadzinski himself is responsible for planning and carrying out tests during the assembly of time projection chamber (TPC), the main detector for LUX-ZEPLIN experiment (LZ). Currently being constructed on the 4850 Level at Sanford Underground Research Facility (Sanford Lab), this main detector consists of a large tank that will hold 7 tonnes of ultra-pure, cryogenic liquid xenon maintained at -100o C. All the pieces of this detector are designed to function with precision; it’s Biesiadzinski job to verify that each part continues to work correctly as they are integrated. That includes hundreds of photomultiplier tubes (PMT).

    Test run

    The most recent test was piecing together an intricate mock array for the PMTs, which will detect light signals created by the collision of a dark matter particle and a xenon atom, inside the main detector. In a soft-wall cleanroom in the Surface Laboratory at Sanford Lab, Biesiadzinski and his team carefully practiced placing instruments like thermometers, sensors and reflective covering. They practiced installing routing cabling, including PMT high voltage power cables, PMT signal cables and thermometer cables.

    “Essentially, we wanted to gain experience so we could be faster during the actual assembly. The faster we work, the more we limit dust exposure and therefore potential backgrounds,” said Biesiadzinski. “It was also an opportunity to test fit real components. We did find that there were some very tight places that motivated us to slightly redesign some small parts to make assembly easier.”

    These tests will make the installment of the actual LZ arrays much smoother.

    “LZ’s main detector will have two PMT arrays, one on the top of the tank and one on the bottom,” Biesiadzinski explained. “The bottom array will hold 241 PMTs pointing up into the liquid Xenon volume of the main detector. The top array will hold PMTs 253 pointing down on the liquid Xenon and the gas layer above it in the main detector.”

    In total, there will be 494 PMTs lining the main detector. If a WIMP streaks through the tank and strikes a xenon nucleus, two things will happen. First, the xenon will emit a flash of light. Then, it will release electrons, which drift in an electric field to the top of the tank, where they will produce a second flash of light. Hundreds of PMTs will be waiting to detect a characteristic combination of flashes from inside the tank—a WIMPs’ telltale signature.

    “Both arrays—top and bottom—record the light from particle interactions inside the detector, including, hopefully, dark matter,” said Biesiadzinski. “This data allows us to estimate both the energy created and 3D location of the interaction.”

    Catching light

    The PMTs used for LZ are extremely sensitive. Not only can they distinguish individual photons of light arriving just a few tens of nanoseconds apart, they can also see the UV light produced by xenon that is far outside the human vision range. The X-Y location of events in the detector can be measured using the top PMT array to within a few millimeters for sufficiently energetic events.

    To insure every bit of light makes its way to a PMT, the inside surfaces of the arrays are covered with Polytetrafluoroethylene (PTFE or teflon), a material highly reflective to xenon scintillation light, in between the PMT faces.

    “This way, photons that don’t enter the PMTs right away—and are therefore not recorded—are reflected and will get a second, third, and so on, chance of being detected as they bounce around the detector,” said Biesiadzinski.

    Researchers will also cover the outside of the bottom array, including all of the cables, with PTFE to maximize light collection there. Light recorded there by additional PMTs that are not part of the array, allow us to measure radioactive backgrounds that can contaminate the main detector.

    Keeping it “clean”

    In addition to being very specific, these PMTs are also ultra-clean.

    “By clean, we mean radio-pure,” said Briana Mount, director of the BHUC, where 338 of LZ’s PMTs have already been tested for radio-purity.

    The tiniest amounts of radioactive elements in the very materials used to construct LZ can also overwhelm the rare-event signal. Radioactive elements can be found in rocks, titanium—even human sweat. As these elements decay, they emit signals that quickly light up ultra-sensitive detectors. To lessen these misleading signatures, researchers assay, or test, their materials for radio-purity using low-background counters (LBCs).

    “Our PMTs are special made to have very low radioactivity so as to not overwhelm a very sensitive detector like LZ with background signal,” said Biesiadzinski.

    Testing the PMTs at the BHUC allows researchers to understand exactly how much of a remaining background they can expect to see from these materials during the experiment. Mount explained that most of the samples currently being assayed at the BHUC are LZ samples, including cable ties, wires, nuts and bolts.

    “We have assayed every component that will make up LZ,” said Kevin Lesko, senior physicist at Lawrence Berkeley National Lab (Berkeley Lab) and a spokesperson for LZ. “At this point we have performed over 1300 assays with another 800 assays planned. These have kept BHUC and the UK’s Boulby LBCs fully occupied for approximately 4 years. These assays permit us ensure no component contributes a major background to the detector and also allows us to assemble a model of the backgrounds for the entire detector before we turn on a single PMT.”

    For a visual description and breakdown of LZ’s design, watch this video created by SLAC.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    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.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    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

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

     
  • richardmitnick 5:34 pm on August 30, 2018 Permalink | Reply
    Tags: , Borexino observatory, , , , , DarkSide experiment, Davide D’Angelo-physical scientist, Fritz Zwicky, , , , , , 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, , Solar neutrinos-recently caught at U Wisconsin IceCube at the South Pole, , , , , , WIMPs that go by names like the gravitino sneutrino and neutralino   

    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.

     
    • Marco Pereira 2:43 pm on September 1, 2018 Permalink | Reply

      I created a theory called the Hypergeometrical Universe Theory (HU). This theory uses three hypotheses:
      a) The Universe is a lightspeed expanding hyperspherical hypersurface. This was later proven correct by observations by the Sloan Digital Sky Survey
      https://hypergeometricaluniverse.quora.com/Proof-of-an-Extra-Spatial-Dimension
      b) Matter is made directly and simply from coherences between stationary states of deformation of the local metric called Fundamental Dilator or FD.
      https://hypergeometricaluniverse.quora.com/The-Fundamental-Dilator
      c) FDs obey the Quantum Lagrangian Principle (QLP). Yves Couder had a physical implementation (approximation) of the Fundamental Dilator and was perplexed that it would behave Quantum Mechanically. FDs and the QLP are the reason for Quantum Mechanics. QLP replaces Newtonian Dynamics and allows for the derivation of Quantum Gravity or Gravity as applied to Black Holes.

      HU derives a new law of Gravitation that is epoch-dependent. That makes Type 1a Supernovae to be epoch-dependent (within the context of the theory). HU then derives the Absolute Luminosity of SN1a as a function of G and showed that Absolute Luminosity scales with G^{-3}.
      Once corrected the Photometrically Determined SN1a distances, HU CORRECTLY PREDICTS all SN1a distances given their redshifts z.

      The extra dimension refutes all 4D spacetime theories, including General Relativity and L-CDM. HU also falsifies all Dark Matter evidence:
      https://www.quora.com/Are-dark-matter-and-dark-energy-falsifiable/answer/Marco-Pereira-1
      including the Spiral Galaxy Conundrum and the Coma Cluster Conundrum.

      Somehow, my theory is still been censored by the community as a whole (either directly or by omission).

      I hope this posting will help correct this situation.

      Like

  • richardmitnick 4:40 pm on May 6, 2018 Permalink | Reply
    Tags: , , , Fritz Zwicky, , , ,   

    From Symmetry: “The origins of dark matter” 

    Symmetry Mag
    From Symmetry

    11/08/16 [Just brought forward in social media]
    Matthew R. Francis

    1
    Artwork by Sandbox Studio, Chicago with Corinne Mucha

    [Because this article is well over a year old, I have updated it with Dark Matter experiments and also included a section on the origins of Dark Matter research by Vera Rubin and Fritz Zicky.]

    Dark Matter Research

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Milky Way Dark Matter Halo Credit ESO L. Calçada


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

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

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

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX/Dark matter experiment at SURF

    Edelweiss Dark Matter Experiment, located at the Modane Underground Laboratory in France

    Transitions are everywhere we look. Water freezes, melts, or boils; chemical bonds break and form to make new substances out of different arrangements of atoms. The universe itself went through major transitions in early times. New particles were created and destroyed continually until things cooled enough to let them survive. Those particles include ones we know about, such as the Higgs boson or the top quark. But they could also include dark matter, invisible particles which we presently know only because of their gravitational effects. In cosmic terms, dark matter particles could be a “thermal relic,” forged in the hot early universe and then left behind during the transitions to more moderate later eras. One of these transitions, known as “freeze-out,” changed the nature of the whole universe.

    The hot cosmic freezer

    On average, today’s universe is a pretty boring place. If you pick a random spot in the cosmos, it’s far more likely to be in intergalactic space than, say, the heart of a star or even inside an alien solar system. That spot is probably cold, dark and quiet. The same wasn’t true for a random spot shortly after the Big Bang. “The universe was so hot that particles were being produced from photons smashing into other photons, of photons hitting electrons, and electrons hitting positrons and producing these very heavy particles,” says Matthew Buckley of Rutgers University. The entire cosmos was a particle-smashing party, but parties aren’t meant to last. This one lasted only a trillionth of a second. After that came the cosmic freeze-out. During the freeze-out, the universe expanded and cooled enough for particles to collide far less frequently and catastrophically. “One of these massive particles floating through the universe is finding fewer and fewer antimatter versions of itself to collide with and annihilate,” Buckley says. “Eventually the universe would get large enough and cold enough that the rate of production and the rate of annihilation basically goes to zero, and you just a relic abundance, these few particles that are floating out there lonely in space.” Many physicists think dark matter is a thermal relic, created in huge numbers in before the cosmos was a half-second old and lingering today because it barely interacts with any other particle.

    A WIMPy miracle

    One reason to think of dark matter as a thermal relic is an interesting coincidence known as the “WIMP miracle.” WIMP stands for “weakly-interacting massive particle,” and WIMPs are the most widely accepted candidates for dark matter. Theory says WIMPs are likely heavier than protons and interact via the weak force, or at least interactions related to the weak force. The last bit is important, because freeze-out for a specific particle depends on what forces affect it and the mass of the particle. Thermal relics made by the weak force were born early in the universe’s history because particles need to be jammed in tight for the weak force, which only works across short distances, to be a factor.

    “If dark matter is a thermal relic, you can calculate how big the interaction [between dark matter particles] needs to be,” Buckley says. Both the primordial light known as the cosmic microwave background [CMB] and the behavior of galaxies tell us that most dark matter must be slow-moving (“cold” in the language of physics).

    COBE CMB


    NASA/COBE 1989 to 1993.


    Cosmic Microwave Background NASA/WMAP


    NASA/WMAP 2001 to 2010


    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    That means interactions between dark matter particles must be low in strength. “Through what is perhaps a very deep fact about the universe,” Buckley says, “that interaction turns out to be the strength of what we know as the weak nuclear force.” That’s the WIMP miracle: The numbers are perfect to make just the right amount of WIMPy matter. The big catch, though, is that experiments haven’t found any WIMPs yet.

    It’s too soon to say WIMPs don’t exist, but it does rule out some of the simpler theoretical predictions about them.

    Ultimately, the WIMP miracle could just be a coincidence. Instead of the weak force, dark matter could involve a new force of nature that doesn’t affect ordinary matter strongly enough to detect. In that scenario, says Jessie Shelton of the University of Illinois at Urbana-Champaign, “you could have thermal freeze-out, but the freeze-out is of dark matter to some other dark field instead of [something in] the Standard Model.” In that scenario, dark matter would still be a thermal relic but not a WIMP. For Shelton, Buckley, and many other physicists, the dark matter search is still full of possibilities. “We have really compelling reasons to look for thermal WIMPs,” Shelton says. “It’s worth remembering that this is only one tiny corner of a much broader space of possibilities.”

    Well, what about AXIONS?

    CERN CAST Axion Solar Telescope


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    Origins of Dark Matter Research

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

    Vera Florence Cooper Rubin was an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. This phenomenon became known as the galaxy rotation problem, and was evidence of the existence of dark matter. Although initially met with skepticism, Rubin’s results were confirmed over subsequent decades. Her legacy was described by The New York Times as “ushering in a Copernican-scale change” in cosmological theory.

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

    Fritz Zwicky, a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy. In 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen dark matter, describing it as “dunkle Materie

    There was no Nobel award for either Rubin or Zwicky.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:53 pm on December 15, 2017 Permalink | Reply
    Tags: A strong pointer to the existence of unknown elementary particles is the movements of stars in galaxies, Cracow HP supercomputer Prometheus, Fritz Zwicky, GAMBIT Collaboration, , , , Righ now only the neutralino is considered a potential candidate for dark matter   

    From phys.org: “GAMBIT project suggests theoretical particles are too massive for LHC detection” 

    physdotorg
    phys.org

    December 15, 2017

    Cracow HP supercomputer Prometheus


    For 80 million working hours, the GAMBIT Collaboration tracked possible clues of ‘new physics’ with the Cracow HP supercomputer Prometheus, confronting the predictions of several models of supersymmetry with data collected by the most sophisticated contemporary scientific experiments. (Source: Cyfronet, AGH) Credit: Cyfronet, AGH

    Standard model of Supersymmetry DESY

    The elementary particles of new theoretical physics must be so massive that their detection in the LHC, the largest modern accelerator, will not be possible. This is the pessimistic conclusion of the most comprehensive review of observational data from many scientific experiments and their confrontation with several popular varieties of supersymmetry theory. The complicated, extremely computationally demanding analysis, carried out by the international GAMBIT Collaboration, leaves a shadow of hope for researchers.

    GAMBIT is the Global and Modular Beyond-the-Standard-Model Inference Tool. Researchers are now questioning whether its is possible for the LHC to detect the elementary particles proposed to explain such mysteries as the nature of dark matter and the lack of symmetry between matter and antimatter. To answer this question, GAMBIT comprehensively analyses data collected during LHC runs. The first results, which are quite intriguing for physicists, have just been published in the European Physical Journal C. The Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow participated in the work of the team.

    Theoretical physicists are convinced that the Standard Model, the current, well-verified theory of the structure of matter, needs to be expanded.

    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.

    A strong pointer to the existence of unknown elementary particles is the movements of stars in galaxies. The Polish astronomer Marian Kowalski was the first to investigate the statistical characteristics of these movements. In 1859, he discovered that the movements of the stars close to us cannot be explained by the movement of the sun itself. This was the first indication of the rotation of the Milky Way (Kowalski is thus the man who “moved the entire galaxy from its foundations”). In 1933, the Swiss astrophysicist Fritz Zwicky took the next step.

    4
    Fritz Zwicky

    From his observation of galaxies in the Coma cluster, he concluded that they move around the clusters as if there were a large amount of invisible matter there.

    Coma cluster via NASA/ESA Hubble

    Although almost a century has passed since Zwicky’s discovery, it is still not possible to investigate the composition of dark matter, nor even to unambiguously confirm its existence. Over this period, theoreticians have constructed many extensions of the Standard Model containing particles that are to a greater or lesser extent exotic. Many of these are candidates for dark matter. The family of supersymmetric theories is popular, for example. Here, certain new equivalents of known particles that are massive and interact weakly with ordinary matter constitute dark matter. Naturally, many groups of experimental physicists are also looking for traces of such new physics. Each of them, based on theoretical assumptions, carries out a certain research project, and then deals with the analysis and interpretation of data flowing from it. This is almost always done in the context of one, usually quite narrow, field of physics, and one theory for what might be beyond the Standard Model.

    “The idea of the GAMBIT Collaboration is to create tools for analyzing data from as many experiments as possible, from different areas of physics, and to compare them very closely with the predictions of new theories. Looking comprehensively, it is possible to narrow the search areas of new physics much faster, and over time also eliminate those models whose predictions have not been confirmed in measurements,” explains Dr. Marcin Chrzaszcz (IFJ PAN).

    The idea to build a set of modular software tools for the global analysis of observational data from physical experiments arose in 2012 in Melbourne during an international conference on high energy physics. Currently, the GAMBIT group includes more than 30 researchers from scientific institutions in Australia, France, Spain, the Netherlands, Canada, Norway, Poland, the United States, Switzerland, Sweden and Great Britain. Dr Chrzaszcz joined the GAMBIT team three years ago in order to develop tools to model the physics of massive quarks, with particular reference to beauty quarks (usually this field of physics has a much more catchy name: heavy flavour physics).

    Verification of the new physics proposals takes place in the GAMBIT Collaboration as follows: Scientists choose a theoretical model and build it into the software. The program then scans the values of the main model parameters. For each set of parameters, predictions are calculated and compared to the data from the experiments.

    “In practice, nothing is trivial here. There are models where we have as many as 128 free parameters. Imagine scanning in a space of 128 dimensions—it’s something that kills every computer. Therefore, at the beginning, we limited ourselves to three versions of simpler supersymmetric models, known under the abbreviations CMSSM, NUHM1 and NUHM2. They have five, six and seven free parameters, respectively. But things nonetheless get complicated, because, for example, we only know some of the other parameters of the Standard Model with a certain accuracy. Therefore, they have to be treated like free parameters too, only changing to a lesser extent than the new physics parameters,” says Dr. Chrzaszcz.

    The scale of the challenge is best demonstrated by the total time taken for all the calculations of the GAMBIT Collaboration to date. They were carried out on the Prometheus supercomputer, one of the fastest computers in the world. The device, operating at the Academic Computer Centre CYFRONET of the University of Science and Technology in Cracow, has over 53,000 processing cores and a total computing power of 2,399 teraflops (a million million floating-point operations per second). Despite the use of such powerful equipment, the total working time of the cores in the GAMBIT Collaboration amounted to 80 million hours (over 9,100 years).

    “Such lengthy calculations are, among other things, a consequence of the diversity of the measured data. For example, groups from the main experiments at the LHC publish exactly the results the detectors measured. But each detector distorts what it sees in some way. Before we compare the data with the predictions of the model being verified, the distortions introduced by the detector must be removed from them,” explains Dr Chrzaszcz, and adds, “On the astrophysics side, we have to perform a similar procedure. For example, simulations should be carried out on how new physics phenomena would affect the behavior of the galactic halo of dark matter.”

    For seekers of new physics, the GAMBIT Collaboration does not bring the best news. The analyses suggest that if the supersymmetric particles predicted by the studied models exist, their masses must be on the order of many teraelectronvolts (in particle physics the mass of particles is given in energy units, one electronvolt corresponds to the energy necessary to shift the electron between points with a potential difference of one volt). In practice, this means that seeing such particles at the LHC will be either very difficult or even impossible. But there is also a shadow of hope. A few superparticles, neutralinos, charginos, staus and stops, although having quite large masses, do not exceed one teraelectronvolt. With some luck, their detection in the LHC remains possible. Unfortunately, in this group, only the neutralino is considered a potential candidate for dark matter.

    Unlike many other analytical research tools, the codes of all the GAMBIT modules are publicly available on the project website and can be quickly adapted to the analysis of new theoretical models. Researchers from the GAMBIT Collaboration hope that the openness of the code will speed up the search for new physics.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: