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  • richardmitnick 2:12 pm on August 27, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “Looking for strings inside inflation” 

    Symmetry

    August 27, 2015
    Troy Rummler

    1

    Theorists from the Institute for Advanced Study have proposed a way forward in the quest to test string theory.

    Two theorists recently proposed a way to find evidence for an idea famous for being untestable: string theory. It involves looking for particles that were around 14 billion years ago, when a very tiny universe hit a growth spurt that used 15 billion times more energy than a collision in the Large Hadron Collider.

    Scientists can’t crank the LHC up that high, not even close. But they could possibly observe evidence of these particles through cosmological studies, with the right technological advances.
    Unknown particles

    During inflation—the flash of hyperexpansion that happened 10-33 seconds after the big bang— particles were colliding with astronomical power. We see remnants of that time in tiny fluctuations in the haze of leftover energy called the cosmic microwave background [CMB].

    Cosmic Background Radiation Planck
    CMB per Planck

    ESA Planck
    ESA/Planck

    Scientists might be able to find remnants of any prehistoric particles that were around during that time as well.

    “If new particles existed during inflation, they can imprint a signature on the primordial fluctuations, which can be seen through specific patterns,” says theorist Juan Maldacena of the Institute for Advanced Study at Princeton University.

    Maldacena and his IAS collaborator, theorist Nima Arkani-Hamed, have used quantum field theory calculations to figure out what these patterns might look like. The pair presented their findings at an annual string theory conference held this year in Bengaluru, India, in June.

    The probable, impossible string

    String theory is frequently summed up by its basic tenet: that the fundamental units of matter are not particles. They are one-dimensional, vibrating strings of energy.

    The theory’s purpose is to bridge a mathematic conflict between quantum mechanics and [Albert] Einstein’s theory of general relativity. Inside a black hole, for example, quantum mechanics dictates that gravity is impossible. Any attempt to adjust one theory to fit the other causes the whole delicate system to collapse. Instead of trying to do this, string theory creates a new mathematical framework in which both theories are natural results. Out of this framework emerges an astonishingly elegant way to unify the forces of nature, along with a correct qualitative description of all known elementary particles.

    As a system of mathematics, string theory makes a tremendous number of predictions. Testable predictions? None so far.

    Strings are thought to be the smallest objects in the universe, and computing their effects on the relatively enormous scales of particle physics experiments is no easy task. String theorists predict that new particles exist, but they cannot compute their masses.

    To exacerbate the problem, string theory can describe a variety of universes that differ by numbers of forces, particles or dimensions. Predictions at accessible energies depend on these unknown or very difficult details. No experiment can definitively prove a theory that offers so many alternative versions of reality.
    Putting string theory to the test

    But scientists are working out ways that experiments could at least begin to test parts of string theory. One prediction that string theory makes is the existence of particles with a unique property: a spin of greater than two.

    Spin is a property of fundamental particles. Particles that don’t spin decay in symmetric patterns. Particles that do spin decay in asymmetric patterns, and the greater the spin, the more complex those patterns get. Highly complex decay patterns from collisions between these particles would have left signature impressions on the universe as it expanded and cooled.

    Scientists could find the patterns of particles with greater than spin 2 in subtle variations in the distribution of galaxies or in the cosmic microwave background, according to Maldacena and Arkani-Hamed. Observational cosmologists would have to measure the primordial fluctuations over a wide range of length scales to be able to see these small deviations.

    The IAS theorists calculated what those measurements would theoretically be if these massive, high-spin particles existed. Such a particle would be much more massive than anything scientists could find at the LHC.

    A challenging proposition

    Cosmologists are already studying patterns in the cosmic microwave background. Experiments such as Planck, BICEP and POLAR BEAR are searching for polarization, which would be evidence that a nonrandom force acted on it.

    BICEP 2
    BICEP 2 interior
    BICEP

    POLARBEAR McGill Telescope
    PolarBear

    If they rewind the effects of time and mathematically undo all other forces that have interacted with this energy, they hope that what pattern remains will match the predicted twists imbued by inflation.

    The patterns proposed by Maldacena and Arkani-Hamed are much subtler and much more susceptible to interference. So any expectation of experimentally finding such signals is still a long way off.

    But this research could point us toward someday finding such signatures and illuminating our understanding of particles that have perhaps left their mark on the entire universe.
    The value of strings

    Whether or not anyone can prove that the world is made of strings, people have proven that the mathematics of string theory can be applied to other fields.

    In 2009, researchers discovered that string theory math could be applied to conventional problems in condensed matter physics. Since then researchers have been applying string theory to study superconductors.

    Fellow IAS theorist Edward Witten, who received the Fields Medal in 1990 for his mathematical contributions to quantum field theory and Supersymmetry, says Maldacena and Arkani-Hamed’s presentation was among the most innovative work he saw at the Strings ‘15 conference.

    Witten and others believe that such successes in other fields indicate that string theory actually underlies all other theories at some deeper level.

    “Physics—like history—does not precisely repeat itself,” Witten says. However, with similar structures appearing at different scales of lengths and energies, “it does rhyme.”

    See the full article here.

    Please help promote STEM in your local schools.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 2:09 pm on August 25, 2015 Permalink | Reply
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    From Symmetry: “All about supernovae” 

    Symmetry

    1
    Twenty years ago, astronomers witnessed one of the brightest stellar explosions in more than 400 years. The titanic supernova, called SN 1987A, blazed with the power of 100 million suns for several months following its discovery on Feb. 23, 1987. Observations of SN 1987A, made over the past 20 years by NASA’s Hubble Space Telescope and many other major ground- and space-based telescopes, have significantly changed astronomers’ views of how massive stars end their lives. Astronomers credit Hubble’s sharp vision with yielding important clues about the massive star’s demise.

    This Hubble telescope image shows the supernova’s triple-ring system, including the bright spots along the inner ring of gas surrounding the exploded star. A shock wave of material unleashed by the stellar blast is slamming into regions along the inner ring, heating them up, and causing them to glow. The ring, about a light-year across, was probably shed by the star about 20,000 years before it exploded.
    Date Released: 22 February 2007
    Source http://hubblesite.org/newscenter/archive/releases/2007/10/image/a/
    Author NASA, ESA, P. Challis, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

    NASA Hubble Telescope
    NASA/ESA Hubble

    Somewhere in the cosmos, a star is reaching the end of its life.

    Maybe it’s a massive star, collapsing under its own gravity. Or maybe it’s a dense cinder of a star, greedily stealing matter from a companion star until it can’t handle its own mass.

    Whatever the reason, this star doesn’t fade quietly into the dark fabric of space and time. It goes kicking and screaming, exploding its stellar guts across the universe, leaving us with unparalleled brightness and a tsunami of particles and elements. It becomes a supernova. Here are ten facts about supernovae that will blow your mind.

    1. The oldest recorded supernova dates back almost 2000 years

    In 185 AD, Chinese astronomers noticed a bright light in the sky. Documenting their observations in the Book of Later Han, these ancient astronomers noted that it sparkled like a star, appeared to be half the size of a bamboo mat and did not travel through the sky like a comet. Over the next eight months this celestial visitor slowly faded from sight. They called it a “guest star.”

    Two millennia later, in the 1960s, scientists found hints of this mysterious visitor in the remnants of a supernova approximately 8000 light-years away. The supernova, SN 185, is the oldest known supernova recorded by humankind.

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    Combined X-ray image from Chandra and XMM-Newton of RCW 86. Low energy X-rays are in red, medium energies in green, and high energies in blue. RCW 86 is the probable remnant of SN 185.

    ESA XMM Newton
    ESA/XMM-Newton

    NASA Chandra Telescope
    NASA/Chandra

    2
    2. Many of the elements we’re made of come from supernovae [This is incorrect. Absolutely everything we are made of was released in a supernova.]

    Everything from the oxygen you’re breathing to the calcium in your bones, the iron in your blood and the silicon in your computer was brewed up in the heart of a star.

    As a supernova explodes, it unleashes a hurricane of nuclear reactions. These nuclear reactions produce many of the building blocks of the world around us. The lion’s share of elements between oxygen and iron comes from core-collapse supernovae, those massive stars that collapse under their own gravity. They share the responsibility of producing the universe’s iron with thermonuclear supernovae, white dwarves that steal mass from their binary companions. Scientists also believe supernovae are a key site for the production of most of the elements heavier than iron.

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    Two men in a rubber raft inspect the wall of photodetectors of the partly filled Super-Kamiokande neutrino detector.

    3. Supernovae are neutrino factories

    In a 10-second period, a core-collapse supernova will release a burst of more than 1058 neutrinos, ghostly particles that can travel undisturbed through almost everything in the universe.

    Outside of the core of a supernova, it would take a light-year of lead to stop a neutrino. But when a star explodes, the center can become so dense that even neutrinos take a little while to escape. When they do escape, neutrinos carry away 99 percent of the energy of the supernova.

    Scientists watch for that burst of neutrinos using an early warning system called SNEWS. SNEWS is a network of neutrino detectors across the world. Each detector is programmed to send a datagram to a central computer whenever it sees a burst of neutrinos. If more than two experiments observe a burst within 10 seconds, the computer issues an automatic alert to the astronomical community to look out for an exploding star.

    But you don’t have to be an expert astronomer to receive an alert. Anyone can sign up to be among the first to know that a star’s core has collapsed.

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

    4. Supernovae are powerful particle accelerators

    Supernovae are natural space laboratories; they can accelerate particles to at least 1000 times the energy of particles in the Large Hadron Collider, the most powerful collider on Earth.

    The interaction between the blast of a supernova and the surrounding interstellar gas creates a magnetized region, called a shock. As particles move into the shock, they bounce around the magnetic field and get accelerated, much like a basketball being dribbled closer and closer to the ground. When they are released into space, some of these high-energy particles, called cosmic rays, eventually slam into our atmosphere, colliding with atoms and creating showers of secondary particles that rain down on our heads.

    5. Supernovae produce radioactivity

    In addition to forging elements and neutrinos, the nuclear reactions inside of supernovae also cook up radioactive isotopes. Some of this radioactivity emits light signals, such as gamma rays, that we can see in space.

    This radioactivity is part of what makes supernovae so bright. It also provides us with a way to determine if any supernovae have blown up near Earth. If a supernova occurred close enough to our planet, we’d be sprayed with some of these unstable nuclei. So when scientists come across layers of sediment with spikes of radioactive isotopes, they know to investigate whether what they’ve found was spit out by an exploding star.

    In 1998, physicists analyzed crusts from the bottom of the ocean and found layers with a surge of 60Fe, a rare radioactive isotope of iron that can be created in copious amounts inside supernovae. Using the rate at which 60Fe decays over time, they were able to calculate how long ago it landed on Earth. They determined that it was most likely dumped on our planet by a nearby supernova about 2.8 million years ago.

    6. A nearby supernova could cause a mass extinction

    If a supernova occurred close enough, it could be pretty bad news for our planet. Although we’re still not sure about all the ways being in the midst of an exploding star would affect us, we do know that supernovae emit truckloads of high-energy photons such as X-rays and gamma rays. The incoming radiation would strip our atmosphere of its ozone. All of the critters in our food chain from the bottom up would fry in the sun’s ultraviolet rays until there was nothing left on our planet but dirt and bones.

    Statistically speaking, a supernova in our own galaxy has been a long time coming.

    Supernovae occur in our galaxy at a rate of about one or two per century. Yet we haven’t seen a supernova in the Milky Way in around 400 years. The most recent nearby supernova was observed in 1987, and it wasn’t even in our galaxy. It was in a nearby satellite galaxy called the Large Magellanic Cloud [LMC].

    5
    LMC

    But death by supernova probably isn’t something you have to worry about in your lifetime, or your children’s or grandchildren’s or great-great-great-grandchildren’s lifetime. IK Pegasi, the closest candidate we have for a supernova, is 150 light-years away—too far to do any real damage to Earth.

    Even that 2.8-million-year-old supernova that ejected its radioactive insides into our oceans was at least 100 light-years from Earth, which was not close enough to cause a mass-extinction. The physicists deemed it a “near miss.”

    7. Supernovae light can echo through time

    Just as your voice echoes when its sound waves bounce off a surface and come back again, a supernova echoes in space when its light waves bounce off cosmic dust clouds and redirect themselves toward Earth.

    Because the echoed light takes a scenic route to our planet, this phenomenon opens a portal to the past, allowing scientists to look at and decode supernovae that occurred hundreds of years ago. A recent example of this is SN1572, or Tycho’s supernova, a supernova that occurred in 1572. This supernova shined brighter than Venus, was visible in daylight and took two years to dim from the sky.

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    Remnant of SN 1572 as seen in X-ray light from the Chandra X-ray Observatory

    In 2008, astronomers found light waves originating from the cosmic demolition site of the original star. They determined that they were seeing light echoes from Tycho’s supernova. Although the light was 20 billion times fainter than what astronomer Tycho Brahe observed in 1572, scientists were able to analyze its spectrum and classify the supernova as a thermonuclear supernova.

    More than four centuries after its explosion, light from this historical supernova is still arriving at Earth.

    5

    8. Supernovae were used to discover dark energy

    Because thermonuclear supernovae are so bright, and because their light brightens and dims in a predictable way, they can be used as lighthouses for cosmology.

    In 1998, scientists thought that cosmic expansion, initiated by the big bang, was likely slowing down over time. But supernova studies suggested that the expansion of the universe was actually speeding up.

    8
    According to the Big Bang model, the universe expanded from an extremely dense and hot state and continues to expand today.

    Scientists can measure the true brightness of supernovae by looking at the timescale over which they brighten and fade. By comparing how bright these supernovae appear with how bright they actually are, scientists are able to determine how far away they are.

    Scientists can also measure the increase in the wavelength of a supernova’s light as it moves farther and farther away from us. This is called the redshift.

    Comparing the redshift with the distances of supernovae allowed scientists to infer how the rate of expansion has changed over the history of the universe. Scientists believe that the culprit for this cosmic acceleration is something called dark energy.

    9. Supernovae occur at a rate of approximately 10 per second

    By the time you reach the end of this sentence, it is likely a star will have exploded somewhere in the universe.

    As scientists evolve better techniques to explore space, the number of supernovae they discover increases. Currently they find over a thousand supernovae per year.

    But when you look deep into the night sky at bright lights shining from billions of light-years away, you’re actually looking into the past. The supernovae that scientists are detecting stretch back to the very beginning of the universe. By adding up all of the supernovae they’ve observed, scientists can figure out the rate at which supernovae occur across the entire universe.

    Scientists estimate about 10 supernovae occur per second, exploding in space like popcorn in the microwave.

    10. We’re about to get much better at detecting far-away supernovae

    Even though we’ve been aware of these exploding stars for millennia, there’s still so much we don’t know about them. There are two known types of supernovae, but there are many different varieties that scientists are still learning about.

    Supernovae could result from the merger of two white dwarfs. Alternatively, the rotation of a star could create a black hole that accretes material and launches a jet through the star. Or the density of a star’s core could be so high that it starts creating electron-positron pairs, causing a chain reaction in the star.

    Right now, scientists are mapping the night sky with the Dark Energy Survey, or DES. Scientists can discover new supernova explosions by looking for changes in the images they take over time.

    Dark Energy Survey
    DECam
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    DES, the DeCam built at FNAL, and the CTIO Victor M Blanco Telescope in Chile in which DECam is housed

    Another survey currently going on is the All-Sky Automated Survey for Supernovae, or the ASAS-SN, which recently observed the most luminous supernova ever discovered.

    All Sky Automated Survey for Supernovas
    ASAS-SN telescope

    In 2019, the Large Synoptic Survey Telescope, or LSST, will revolutionize our understanding of supernovae. LSST is designed to collect more light and peer deeper into space than ever before. It will move rapidly across the sky and take more images in larger chunks than previous surveys. This will increase the number of supernovae we see by hundreds of thousands per year.

    LSST Exterior
    LSST Telescope
    LSST Camera
    LSST home and telescope to be biuilt in Chile

    Studying these astral bombs will expand our knowledge of space and bring us even closer to understanding not just our origin, but the cosmic reach of the universe.

    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 11:31 am on August 20, 2015 Permalink | Reply
    Tags: , , , , , Symmetry Magazine   

    From Symmetry: Q&A: Marcelle Soares-Santos 

    Symmetry

    August 20, 2015
    Leah Hesla

    Scientist Marcelle Soares-Santos talks about Brazil, neutron stars and a love of discovery.

    6
    Photo by Reidar Hahn, Fermilab

    Marcelle Soares-Santos has been exploring the cosmos since she was an undergraduate at the Federal University of Espirito Santo in southeast Brazil. She received her PhD from the University of São Paulo and is currently an astrophysicist on the Dark Energy Survey based at Fermi National Accelerator Laboratory outside Chicago.

    Soares-Santos has worked at Fermilab for only five years, but she has already made a significant impact: In 2014, she was bestowed the Alvin Tollestrup Award for postdoctoral research. Now she is embarking on a new study to measure gravitational waves from neutron star collisions.

    S: You recently attended the LISHEP conference, a high-energy physics conference held annually in Brazil. This year it was held in the region of Manaus, near your childhood home. What was it like to grow up there?

    MS: Manaus is very different from the region that I think most foreigners know, Rio or São Paulo, but it’s very beautiful, very interesting. When I was four, my father worked for a mining company, and they found a huge reserve of iron ore in the middle of the Amazon forest. All over Brazil, people got offers from that company to get some extra benefits, which was very good for us because one of the benefits was a chance to go a good school there.

    S: When did you get interested in physics?

    MS: That was very early on, when I was a little kid. I didn’t know that it was physics I wanted to do, but I knew I wanted to do science. I tend to say that I lacked any other talents. I could not play any sport, I wasn’t good in the arts. But math and science, that was something I was good at.

    These days I look back and feel that, had I known what I know today, I might not have had this confidence, because I understand now how lots of people are not encouraged to view physics as a topic they can handle. But back then I had a little bit of blind faith in the school system.

    S: You work on the Dark Energy Survey. When did the interest in astrophysics kick in?

    MS: I did an undergraduate research project. In Brazil, there is a program of research initiation where undergraduates can work for an entire year on a particular topic. My supervisor’s research was related to dark energy and gravitational waves. It’s interesting, because today I work on those two topics from a completely different perspective.

    Dark Energy Icon
    Dark Energy Camera
    Dark Energy camera (DECam) built at FNAL and housed in the CTIO Victor M Blanco 4 meter telescope in Chile
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco telescope

    S: You’re also starting on a new project to study gravitational waves. What’s that about?

    MS: For the first time we are building detectors that will be able to detect gravitational waves, not from cosmological sources, but from colliding neutron stars. These events are very rare, but we know they occur, and we can calculate how much gravitational wave emission there will be. The detectors are now reaching the sensitivity that they can see that. There’s LIGO in the United States and Virgo collaboration in Europe.

    Caltech LIGO
    LIGOVIRGO interferometer EGO Campus
    VIRGO

    Relying solely on gravitational waves, it’s possible only to roughly localize in the sky where the star collision happens. But we also have the Dark Energy Camera, so we can use it to find the optical counterpart—lots and lots of photons—and pinpoint the event picked up by the gravitational wave detector.

    If we see the collision, we will be the first ones to see it based on a gravitational wave signal. That will be really cool.

    S: How did the project get started? What is it called?

    MS: I saw an announcement that LIGO was going to start operating this year, and I thought, “DECam would be great for this.” I talked to Jim Annis [at Fermilab] and said, “Look, look at this. It would be cool.” And he said, “Yeah, it would.”

    It’s called the DES-GW project. It will start up in September. Groups from Fermilab, the University of Chicago, University of Pennsylvania and Harvard are participating.

    S: What’s your favorite thing about what you do?

    MS: Building these crazy ideas to become a reality. That’s the fun part of it. Of course, it’s not always possible, and we have more ideas than we can actually realize, but if you get to do one, it’s really cool. Part of the reason I moved from theory [as a graduate student] to experiment is that I wanted to do something where you actually get to close the loop of answering a question.

    S: Has anything about being a scientist surprised you?

    MS: In the beginning I thought I’d never be the person doing hands-on work on detector. I thought of myself more as someone who would be sitting in front of a computer. And it’s true that I spend most of my time sitting in front of the computer, but I also get a chance to go to Chile [where the Dark Energy Camera is located] and take data, be at the lab and get my hands dirty. Back then I thought that was more the role of an engineer than a scientist. I learned it doesn’t matter the label. It is a part of the job, and it’s a fun part.

    S:In June 2014 Fermilab posted a Facebook post about you winning the Alvin Tollestrup Award. It received by far more likes than any Fermilab post up to that point, and most were pouring in from Brazil. What was behind its popularity?

    MS:That was surprising for me. Typically whenever there is something on Facebook related to what I do, my parents will be excited about it and repost, so I get a few likes and reposts from relatives and friends. This one, I don’t know what happened. I think in part there was a little bit of pride, people seeing a Brazilian being successful abroad.

    I got lots of friend requests from people I’ve never met before. I got questions from high schoolers about physics and how to pursue a physics education. It’s a big responsibility to say something. What do you say to people? I tried to answer reasonably and tell them my experience. It was my 15 minutes of fame in social media.

    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 11:39 am on August 18, 2015 Permalink | Reply
    Tags: Age of the universe, , , Symmetry Magazine   

    From Symmetry: “The age of the universe” 

    Symmetry

    August 18, 2015
    Amelia Williamson Smith

    Looking out from our planet at the vast array of stars, humans have always asked questions central to our origin: How did all of this come to be? Has it always existed? If not, how and when did it begin?

    How can we determine the history of something so complex when we were not around to witness its birth?

    Scientists have used several methods: checking the age of the oldest objects in the universe, determining the expansion rate of the universe to trace backward in time, and using measurements of the cosmic microwave background [CMB]to figure out the initial conditions of the universe and its evolution.

    Cosmic Background Radiation Planck
    CMB per Planck

    ESA Planck
    ESA/Planck

    2

    Hubble and an expanding universe

    NASA Hubble Telescope
    NASA/ESA Hubble

    In the early 1900s, there was no such concept of the age of the universe, says Stanford University associate professor Chao-Lin Kuo of SLAC National Accelerator Laboratory. “Philosophers and physicists thought the universe had no beginning and no end.”

    Then in the 1920s, mathematician Alexander Friedmann predicted an expanding universe. Edwin Hubble confirmed this when he discovered that many galaxies were moving away from our own at high speeds. Hubble measured several of these galaxies and in 1929 published a paper stating the universe is getting bigger.

    Scientists then realized that they could wind this expansion back in time to a point when it all began. “So it was not until Friedmann and Hubble that the concept of a birth of the universe started,” Kuo says.

    Tracing the expansion of the universe back in time is called finding its “dynamical age,” says Nobel Laureate Adam Riess, professor of astronomy and physics at Johns Hopkins University.

    “We know the universe is expanding, and we think we understand the expansion history,” he says. “So like a movie, you can run it backwards until everything is on top of everything in the big bang.”

    The expansion rate of the universe is known as the Hubble constant.

    The Hubble puzzle

    The Hubble constant has not been easy to measure, and the number has changed several times since the 1930s, Kuo says.

    One way to check the Hubble constant is to compare its prediction for the age of the universe with the age of the oldest objects we can see. At the very least, the universe should be older than the objects it contains.

    Scientists can estimate the age of very old stars that have burned out—called white dwarfs—by determining how long they have been cooling. Scientists can also estimate the age of globular clusters, large clusters of old stars that formed at roughly the same time.

    They have estimated the oldest objects to be between 12 billion and 13 billion years old.

    In the 1990s, scientists were puzzled when they found that their estimate of the age of the universe—based on their measurement of the Hubble constant—was several billion years younger than the age of these oldest stars.

    However, in 1998, Riess and colleagues Saul Perlmutter of Lawrence Berkeley National Laboratory and Brian Schmidt of the Australian National Lab found the root of the problem: The universe wasn’t expanding at a steady rate. It was accelerating.

    They figured this out by observing a type of supernova, the explosion of a star at the end of its life. Type 1a supernovae explode with uniform brightness, and light travels at a constant speed. By observing several different Type 1a supernovae, the scientists were able to calculate their distance from the Earth and how long the light took to get here.

    “Supernovae are used to determine how fast the universe is expanding around us,” Riess says. “And by looking at very distant supernovae that exploded in the past and whose light has taken a long time to reach us, we can also see how the expansion rate has recently been changing.”

    Using this method, scientists have estimated the age of the universe to be around 13.3 billion years.

    Recipe for the universe

    Another way to estimate the age of the universe is by using the cosmic microwave background, radiation left over from just after the big bang that extends in every direction.

    “The CMB tells you the initial conditions and the recipe of the early universe—what kinds of stuff it had in it,” Riess says. “And if we understand that well enough, in principle, we can predict how fast the universe made that stuff with those initial conditions and how the universe would expand at different points in the future.”

    Using NASA’s Wilkinson Microwave Anisotropy Probe, scientists created a detailed map of the minute temperature fluctuations in the CMB. They then compared the fluctuation pattern with different theoretical models of the universe that predict patterns of CMB. In 2003 they found a match.

    NASA WMAP
    WMAP

    Cosmic Microwave Background WMAP
    CMB per WMAP

    “Using these comparisons, we have been able to figure out the shape of the universe, the density of the universe and its components,” Kuo says. WMAP found that ordinary matter makes up about 4 percent of the universe; dark matter is about 23 percent; and the remaining 73 percent is dark energy. Using the WMAP data, scientists estimated the age of the universe to be 13.772 billion years, plus or minus 59 million years.

    In 2013, the European Space Agency’s Planck space telescope created an even more detailed map of the CMB temperature fluctuations and estimated the universe to be 13.82 billion years old, plus or minus 50 million years—slightly older than WMAP’s estimate. Planck also made more detailed measurements of the components of the universe and found slightly less dark energy (around 68 percent) and slightly more dark matter (around 27 percent).

    New puzzles

    Even with these extremely precise measurements, scientists still have puzzles to solve. The measured current expansion rate of the universe tends to be about 5 percent higher than what is predicted from the CMB, and scientists are not sure why, Riess says.

    “It could be a sign that we do not totally understand the physics of the universe, or it could be an error in either of the two measurements,” Riess says.

    “It is a sign of tremendous progress in cosmology that we get upset and worried about a 5 percent difference, whereas 15 or 20 years ago, measurements of the expansion rate could differ by a factor of two.”

    There is also much left to understand about dark matter and dark energy, which appear to make up about 95 percent of the universe. “Our best chance to understand the nature of these unknown dark components is by making these kinds of precise measurements and looking for small disagreements or a loose thread that we can pull on to see if the sweater unravels.”

    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 10:57 am on August 5, 2015 Permalink | Reply
    Tags: , , , Symmetry Magazine   

    From Symmetry: “The mystery of particle generations” 

    Symmetry

    August 05, 2015
    Matthew R. Francis

    Why are there three almost identical copies of each particle of matter?

    1
    Artwork by Sandbox Studio, Chicago

    The Standard Model of particles and interactions is remarkably successful for a theory everyone knows is missing big pieces.

    1
    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.

    It accounts for the everyday stuff we know like protons, neutrons, electrons and photons, and even exotic stuff like Higgs bosons and top quarks. But it isn’t complete; it doesn’t explain phenomena such as dark matter and dark energy.

    The Standard Model is successful because it is a useful guide to the particles of matter we see. One convenient pattern that has proven valuable is generations. Each particle of matter seems to come in three different versions, differentiated only by mass.

    Scientists wonder whether that pattern has a deeper explanation or if it’s just convenient for now, to be superseded by a deeper truth.
    The next generations

    The Standard Model is a menu listing all of the known fundamental particles: particles that cannot be broken down into constituent parts. It distinguishes between the fermions, which are particles of matter, and the bosons, which carry forces.

    The matter particles include six quarks and six leptons. The six quarks are called the up, down, charm, strange, top and bottom quark. Quarks typically don’t exist as single particles but lump together to form heavier particles such as protons and neutrons. Leptons include electrons and their cousins the muons and tau particles, along with the three types of neutrinos.

    All of these matter particles fall into three “generations.”

    “The three generations are literally copy-paste of the first generation,” says Carleton University physicist Heather Logan. The up, charm and top quarks have the same electric charge, along with the same weak and strong interactions—they primarily differ in the mass, which comes from the Higgs field. The same thing holds for the down, strange and bottom quarks, along with the electron, muon and tau leptons.

    “The fact that the three generations couple differently to the Higgs sector is maybe telling us something, but we don’t really know what yet,” Logan says. Most of the generations differ in mass by a lot. For example, the tau lepton is roughly 3600 times more massive than the electron, and the top quark is nearly 100,000 times heavier than the up quark. That difference manifests itself in stability: The heavier generations decay into the lighter generations, until they reach the lightest, which are (as far as we can tell) stable forever.

    The generations play a big role in experiments. The Higgs boson, for instance, is an unstable particle that decays into a variety of other particles, including tau leptons. “Since the tau is the heaviest, the Higgs [boson] prefers to change into taus more than electrons or muons,” says Clara Nellist, an experimental particle physicist at the Laboratoire de l’Accélérateur Linéaire (LAL) in Orsay, France. “The best way to study how the Higgs interacts with leptons is by looking at a Higgs changing into two taus.”

    That sort of observation is the heart of Standard Model physics: Crash two or more particles together, watch what new particles are born, look for patterns in the detritus, and—if we’re really lucky—see what doesn’t fit into the map we have.
    Roads outward

    While some stuff like dark matter obviously lies outside the charts, the Standard Model itself has a few problems. For example, neutrinos should be massless according to the Standard Model, but real-world experiments show they have very tiny masses. And unlike quarks and electrically charged leptons, the mass differences between the generations of neutrinos are very small, which is why we see them oscillating from one type to another.

    Without mass, neutrinos are exactly identical; with the mass, they’re different. And that generational difference is puzzling to theorist Richard Ruiz of the University of Pittsburgh. “There is a pattern here staring at us but we cannot quite figure out how to make sense of it.”

    Even if there is only the one Standard Model Higgs, we can learn a lot by how it interacts and decays. For instance, Nellist says, “by studying how often the Higgs boson changes into taus compared to other particles, we can test the validity of the Standard Model and see if there are hints of other generations.”

    It’s unlikely, since any fourth generation quark would need to be far more massive even than the top quark. But any anomaly in Higgs decay could tell us a lot.

    “Nobody knows why there are three generations,” Logan says. However, the structure of the Standard Model is a clue to what might be beyond, including the theory known as Supersymmetry: “If there are supersymmetric partners of the fermions, they should also fall into the three generations. How their masses are set might give us clues to understanding how the masses of the Standard Model fermions are set and why we have those patterns.”

    No matter how many there are, nobody knows why there are generations to begin with. “‘Generations’ is just a conventional organization of the Standard Model’s matter content,” Ruiz says. That organization might survive in a deeper theory (for instance, theories in which quarks are made up of smaller particles called “preons”, which are unlikely based on present data), but new ideas would have to explain why the quarks and leptons seem to fall into the patterns they do.

    Ultimately, even though the Standard Model is not the final description of the cosmos, it’s been a good guide so far. As we look for the edges of the map it provides, we get closer to a true and accurate chart of all the particles and their interactions.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 7:47 pm on August 4, 2015 Permalink | Reply
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    From Symmetry: “IceCube sees highest-energy neutrino ever found” 

    Symmetry

    August 04, 2015
    Kathryn Jepsen

    Observations of this kind could lead scientists to the source of ultra-high-energy cosmic rays.

    https://i0.wp.com/www.symmetrymagazine.org/sites/default/files/styles/lead_image/public/images/standard/IceCube_Aurora.jpg
    Photo by Ian Rees, IceCube/NSF

    In 2013, the IceCube neutrino experiment at the South Pole reported the observation of two ultra-high-energy neutrino events, which they named after Sesame Street characters Bert and Ernie. Later, they found one more.

    It seems a fourth character has moved into the neighborhood. Today IceCube scientists reported the observation of an even higher-energy neutrino event, one that offers scientists the best hope yet that they will be able to use ultra-high-energy neutrinos to find the source of ultra-high-energy cosmic rays. The neutrino event had an energy of more than 2000 trillion electronvolts.

    “We have been adding to our previous analysis more years of data, and in an extra year we found this spectacular event,” says Francis Halzen, IceCube principle investigator for the University of Wisconsin, Madison.

    For more than a century, scientists have known that particles called cosmic rays rain down on the Earth from space. Some of these cosmic rays slam into our atmosphere at energies higher than we could possibly reach in any earthly particle accelerator. It is still a mystery where these particles come from, but it seems that they are from energetic sources outside our galaxy. One suspicion is that they are coming from active galaxies swirling around distant black holes.

    Cosmic rays are charged particles, which means that their paths bend and shift as they pass through magnetic fields in space. That makes it difficult to trace their origins.

    That’s where neutrinos come in. Neutrinos are neutral, rarely interacting particles that can pass through entire planets without changing course. Ultra-high-energy neutrinos that the IceCube experiment observes could be coming from the same sources as ultra-high-energy cosmic rays. If so, they could point the way back to those sources.

    “This opens the neutrino astronomy field,” says Fermilab neutrino scientist Anne Schukraft, a former member of the IceCube collaboration.

    Neutrinos come in three types, called flavors: electron, muon and tau. When electron and tau neutrinos interact with the ice around the IceCube neutrino detector, their energy appears to balloon out from their interaction points, making it difficult to figure out exactly where they came from.

    This latest ultra-high-energy neutrino, however, was a muon neutrino. When muon neutrinos interact, they release a muon, a heavy cousin of the electron that can travel straight through matter for several kilometers before running out of steam.

    In this case, a neutrino passed through the Earth and interacted somewhere outside of the IceCube detector. The muon it released passed through it, drawing a distinct line to show where it came from.

    From there, “Standard Model physics can run the movie backwards,” Halzen says.

    1
    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.

    The muon they detected had an energy of more than 2000 trillion electronvolts; the neutrino that produced it likely had about three times that energy. The only known source of such a high-energy muon coming through the Earth is a muon neutrino.

    The detector originally picked up the event on June 11, 2014. The IceCube collaboration conducts a blind analysis of its data, which means that it looks at it in large batches, in this case collected over a couple of years.

    When they looked at their data, they sent an alert to scientists working on the HAWC Gamma-Ray Observatory, an array that collects gamma-ray data from a large range of the sky over time.

    HAWC High Altitude Cherenkov Experiment
    HAWC High Altitude Cherenkov Experiment

    Scientists have already looked through HAWC 2014 data for an associated gamma-ray signal, says gamma-ray scientist Werner Hofmann of the Max Planck Institute for Nuclear Physics in Germany.

    From here on out, Halzen says, the IceCube collaboration will send alerts to other experiments that study gamma rays as soon as possible after detecting an ultra-high-energy neutrino event.

    “We are now going to announce events in real time,” Halzen says. “We’re going to bring out events like this hopefully in minutes.”

    That way even telescopes like the VERITAS telescope or the Fermi Gamma-ray Space Telescope will be able to point in the right direction to try to find a signal. Halzen says he expects these “astronomical telegrams” to come about once per month.

    Additional reporting contributed by Ali Sundermier.

    See the full article here.

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  • richardmitnick 3:00 pm on July 30, 2015 Permalink | Reply
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    From Symmetry: “One Higgs is the loneliest number” 

    Symmetry

    July 30, 2015.
    Katie Elyce Jones

    Physicists discovered one type of Higgs boson in 2012. Now they’re looking for more.

    1

    When physicists discovered the Higgs boson in 2012, they declared the Standard Model of particle physics complete; they had finally found the missing piece of the particle puzzle.

    2
    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.

    And yet, many questions remain about the basic components of the universe, including: Did we find the one and only type of Higgs boson? Or are there more?

    A problem of mass

    The Higgs mechanism gives mass to some fundamental particles, but not others. It interacts strongly with W and Z bosons, making them massive. But it does not interact with particles of light, leaving them massless.

    These interactions don’t just affect the mass of other particles, they also affect the mass of the Higgs. The Higgs can briefly fluctuate into virtual pairs of the particles with which it interacts.

    Scientists calculate the mass of the Higgs by multiplying a huge number—related to the maximum energy for which the Standard Model applies—with a number related to those fluctuations. The second number is determined by starting with the effects of fluctuations to force-carrying particles like the W and Z bosons, and subtracting the effects of fluctuations to matter particles like quarks.

    While the second number cannot be zero because the Higgs must have some mass, almost anything it adds up to, even at very small numbers, makes the mass of the Higgs gigantic.

    But it isn’t. It weighs about 125 billion electronvolts; it’s not even the heaviest fundamental particle.

    “Having the Higgs boson at 125 GeV is like putting an ice cube into a hot oven and it not melting,” says Flip Tanedo, a theoretical physicist and postdoctoral researcher at the University of California, Irvine.

    A lightweight Higgs, though it makes the Standard Model work, doesn’t necessarily make sense for the big picture. If there are multiple Higgses—much heavier ones—the math determining their masses becomes more flexible.

    “There’s no reason to rule out multiple Higgs particles,” says Tim Tait, a theoretical physicist and professor at UCI. “There’s nothing in the theory that says there shouldn’t be more than one.”

    The two primary theories that predict multiple Higgs particles are Supersymmetry and compositeness.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Supersymmetry

    Popular in particle physics circles for tying together all the messy bits of the Standard Model, Supersymmetry predicts a heavier (and whimsically named) partner particle, or “sparticle,” for each of the known fundamental particles. Quarks have squarks and Higgs have Higgsinos.

    “When the math is re-done, the effects of the particles and their partner particles on the mass of the Higgs cancel each other out and the improbability we see in the Standard Model shrinks and maybe even vanishes,” says Don Lincoln, a physicist at Fermi National Accelerator Laboratory.

    The Minimal Supersymmetric Standard Model—the supersymmetric model that most closely aligns with the current Standard Model—predicts four new Higgs particles in addition to the Higgs sparticle, the Higgsino.

    While Supersymmetry is maybe the most popular theory for exploring physics beyond the Standard Model, physicists at the LHC haven’t seen any evidence of it yet. If Supersymmetry exists, scientists will need to produce more massive particles to observe it.

    “Scientists started looking for Supersymmetry five years ago in the LHC,” says Tanedo. “But we don’t really know where they will find it: 10 TeV? 100 TeV?”

    Compositeness

    The other popular theory that predicts multiple Higgs bosons is compositeness. The composite Higgs theory proposes that the Higgs boson is not a fundamental particle but is instead made of smaller particles that have not yet been discovered.

    “You can think of this like the study of the atom,” says Bogdan Dobrescu, a theoretical physicist at Fermi National Accelerator Laboratory. “As people looked closer and closer, they found the proton and neutron. They looked closer again and found the ‘up’ and ‘down’ quarks that make up the proton and neutron.”

    Composite Higgs theories predict that if there are more fundamental parts to the Higgs, it may assume a combination of masses based on the properties of these smaller particles.

    The search for composite Higgs bosons has been limited by the scale at which scientists can study given the current energy levels at the LHC.

    On the lookout

    Physicists will continue their Higgs search with the current run of the LHC.

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

    At 60 percent higher energy, the LHC will produce Higgs bosons more frequently this time around. It will also produce more top quarks, the heaviest particles of the Standard Model. Top quarks interact energetically with the Higgs, making them a favored place to start picking at new physics.

    Whether scientists find evidence for Supersymmetry or a composite Higgs (if they find either), that discovery would mean much more than just an additional Higgs.

    “For example, finding new Higgs bosons could affect our understanding of how the fundamental forces unify at higher energy,” Tait says.

    “Supersymmetry would open up a whole ‘super’ world out there to discover. And a composite Higgs might point to new rules on the fundamental level beyond what we understand today. We would have new pieces of the puzzle to look at it.”

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 11:20 am on July 28, 2015 Permalink | Reply
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    From Symmetry: “Is this the only universe?” 

    Symmetry

    July 28, 2015
    Laura Dattaro

    1
    Artwork by Sandbox Studio, Chicago with Ana Kova

    Human history has been a journey toward insignificance.

    As we’ve gained more knowledge, we’ve had our planet downgraded from the center of the universe to a chunk of rock orbiting an average star in a galaxy that is one among billions.

    So it only makes sense that many physicists now believe that even our universe might be just a small piece of a greater whole. In fact, there may be infinitely many universes, bubbling into existence and growing exponentially. It’s a theory known as the multiverse.

    One of the best pieces of evidence for the multiverse was first discovered in 1998, when physicists realized that the universe was expanding at ever increasing speed. They dubbed the force behind this acceleration dark energy. The value of its energy density, also known as the cosmological constant, is bizarrely tiny: 120 orders of magnitude smaller than theory says it should be.

    For decades, physicists have sought an explanation for this disparity. The best one they’ve come up with so far, says Yasunori Nomura, a theoretical physicist at the University of California, Berkeley, is that it’s only small in our universe. There may be other universes where the number takes a different value, and it is only here that the rate of expansion is just right to form galaxies and stars and planets where people like us can observe it. “Only if this vacuum energy stayed to a very special value will we exist,” Nomura says. “There are no good other theories to understand why we observe this specific value.”

    For further evidence of a multiverse, just look to string theory, which posits that the fundamental laws of physics have their own phases, just like matter can exist as a solid, liquid or gas. If that’s correct, there should be other universes where the laws are in different phases from our own—which would affect seemingly fundamental values that we observe here in our universe, like the cosmological constant. “In that situation you’ll have a patchwork of regions, some in this phase, some in others,” says Matthew Kleban, a theoretical physicist at New York University.

    These regions could take the form of bubbles, with new universes popping into existence all the time. One of these bubbles could collide with our own, leaving traces that, if discovered, would prove other universes are out there. We haven’t seen one of these collisions yet, but physicists are hopeful that we might in the not so distant future.

    If we can’t find evidence of a collision, Kleban says, it may be possible to experimentally induce a phase change—an ultra-high-energy version of coaxing water into vapor by boiling it on the stove. You could effectively prove our universe is not the only one if you could produce phase-transitioned energy, though you would run the risk of it expanding out of control and destroying the Earth. “If those phases do exist—if they can be brought into being by some kind of experiment—then they certainly exist somewhere in the universe,” Kleban says.

    No one is yet trying to do this.

    There might be a (relatively) simpler way. Einstein’s general theory of relativity implies that our universe may have a “shape.” It could be either positively curved, like a sphere, or negatively curved, like a saddle. A negatively curved universe would be strong evidence of a multiverse, Nomura says. And a positively curved universe would show that there’s something wrong with our current theory of the multiverse, while not necessarily proving there’s only one. (Proving that is a next-to-impossible task. If there are other universes out there that don’t interact with ours in any sense, we can’t prove whether they exist.)

    In recent years, physicists have discovered that the universe appears almost entirely flat. But there’s still a possibility that it’s slightly curved in one direction or the other, and Nomura predicts that within the next few decades, measurements of the universe’s shape could be precise enough to detect a slight curvature. That would give physicists new evidence about the nature of the multiverse. “In fact, this evidence will be reasonably strong since we do not know any other theory which may naturally lead to a nonzero curvature at a level observable in the universe,” Nomura says.

    If the curvature turned out to be positive, theorists would face some very difficult questions. They would still be left without an explanation for why the expansion rate of the universe is what it is. The phases within string theory would also need re-examining. “We will face difficult problems,” Nomura says. “Our theory of dark energy is gone if it’s the wrong curvature.”

    But with the right curvature, a curved universe could reframe how physicists look at values that, at present, appear to be fundamental. If there were different universes with different phases of laws, we might not need to seek fundamental explanations for some of the properties our universe exhibits.

    And it would, of course, mean we are tinier still than we ever imagined. “It’s like another step in this kind of existential crisis,” Kleban says. “It would have a huge impact on people’s imaginations.”

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 5:43 pm on July 27, 2015 Permalink | Reply
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    From Symmetry: “W bosons remain left-handed” 

    Symmetry

    July 27, 2015
    Sarah Charley

    1
    LHCb. Courtesy of CERN

    A new result from the LHCb collaboration weakens previous hints at the existence of a new type of W boson.

    A measurement released today by the LHCb collaboration dumped some cold water on previous results that suggested an expanded cast of characters mediating the weak force.

    The weak force is one of the four fundamental forces, along with the electromagnetic, gravitational and strong forces. The weak force acts on quarks, fundamental building blocks of nature, through particles called W and Z bosons.

    2
    The Feynman diagram for beta decay of a neutron into a proton, electron, and electron antineutrino via an intermediate heavy W boson

    3
    A Feynman diagram showing the exchange of a pair of W bosons. This is one of the leading terms contributing to neutral Kaon oscillation

    Just like a pair of gloves, particles can in principle be left-handed or right-handed. The new result from LHCb presents evidence that the W bosons that mediate the weak force are all left-handed; they interact only with left-handed quarks.

    This weakens earlier hints from the Belle and BaBar experiments of the existence of right-handed W bosons.

    The LHCb experiment at the Large Hadron Collider examined the decays of a heavy and unstable particle called Lambda-b—a baryon consisting of an up quark, down quark and bottom quark.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    Weak decays can change a bottom quark into either a charm quark, about 1 percent of the time, or into a lighter up quark. The LHCb experiment measured how often the bottom quark in this particle transformed into an up quark, resulting in a proton, muon and neutrino in the final state.

    “We found no evidence for a new right-handed W boson,” says Marina Artuso, a Professor of Physics at Syracuse University and a scientist working on the LHCb experiment.

    If the scientists on LHCb had seen bottom quarks turning into up quarks more often than predicted, it could have meant that a new interaction with right-handed W bosons had been uncovered, Artuso says. “But our measured value agreed with our model’s value, indicating that the right-handed universe may not be there.”

    Earlier experiments by the Belle and BaBar collaborations studied transformations of bottom quarks into up quarks in two different ways: in studies of a single, specific type of transformation, and in studies that ideally included all the different ways the transformation occurs.

    If nothing were interfering with the process (like, say, a right-handed W boson), then these two types of studies would give the same value of the bottom-to-up transformation parameter. However, that wasn’t the case.

    The difference, however, was small enough that it could have come from calculations used in interpreting the result. Today’s LHCb result makes it seem like right-handed W bosons might not exist after all, at least not in a way that is revealed in these measurements.

    Michael Roney, spokesperson for the BaBar experiment, says, “This result not only provides a new, precise measurement of this important Standard Model parameter, but it also rules out one of the interesting theoretical explanations for the discrepancy… which still leaves us with this puzzle to solve.”

    See the full article here.

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  • richardmitnick 1:25 pm on July 23, 2015 Permalink | Reply
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    From Symmetry: “A new first for T2K” 

    Symmetry

    July 23, 2015
    Kathryn Jepsen

    1
    Courtesy of Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo

    The Japan-based neutrino experiment has seen its first three candidate electron antineutrinos

    Scientists on the T2K neutrino experiment in Japan announced today that they have spotted their first possible electron antineutrinos.

    When the T2K experiment first began taking data in January 2010, it studied a beam of neutrinos traveling 295 kilometers from the J-PARC facility in Tokai, on the east coast, to the Super-Kamiokande detector in Kamioka in western Japan. Neutrinos rarely interact with matter, so they can stream straight through the earth from source to detector.

    From May 2014 to June 2015, scientists used a different beamline configuration to produce predominantly the antimatter partners of neutrinos, antineutrinos. After scientists eliminated signals that could have come from other particles, three candidate electron antineutrino events remained.

    T2K scientists hope to determine if there is a difference in the behavior of neutrinos and antineutrinos.

    “That is the holy grail of neutrino physics,” says Chang Kee Jung of State University of New York at Stony Brook, who until recently served as international co-spokesperson for the experiment.

    If scientists caught neutrinos and their antiparticles acting differently, it could help explain how matter came to dominate over antimatter after the big bang. The big bang should have produced equal amounts of each, which would have annihilated one another completely, leaving nothing to form our universe. And yet, here we are; scientists are looking for a way to explain that.

    “In the current paradigm of particle physics, this is the best bet,” Jung says.

    Scientists have previously seen differences in the ways that other matter and antimatter particles behave, but the differences have never been enough to explain our universe. Whether neutrinos and antineutrinos act differently is still an open question.

    Neutrinos come in three types: electron neutrinos, muon neutrinos and tau neutrinos. As they travel, they morph from one type to another. T2K scientists want to know if there’s a difference between the oscillations of muon neutrinos and muon antineutrinos. A possible upgrade to the Super-Kamiokande detector could help with future data-taking.

    One other currently operating experiment can look for this matter-antimatter difference: the [FNAL] NOvA experiment, which studies a beam that originates at Fermilab near Chicago with a detector near the Canadian border in Minnesota.

    FNAL NOvA experiment
    FNAL NOvA

    “This result shows the principle of the experiment is going to work,” says Indiana University physicist Mark Messier, co-spokesperson for the NOvA experiment. “With more data, we will be on the path to answering the big questions.”

    It might take T2K and NOvA data combined to get scientists closer to the answer, Jung says, and it will likely take until the construction of the even larger DUNE neutrino experiment in South Dakota to get a final verdict.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
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