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  • richardmitnick 12:25 pm on December 5, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From physicsworld: “Planck offers another glimpse of the early universe” 

    physicsworld
    physicsworld.com

    Dec 4, 2014
    Tushna Commissariat

    Results of four years of observations made by the Planck space telescope provide the most precise confirmation so far of the Standard Model of cosmology, and also place new constraints on the properties of potential dark-matter candidates. That is the conclusion of astronomers working on the €700m mission of the European Space Agency (ESA). Planck studies the intensity and the polarization of the cosmic microwave background (CMB), which is the thermal remnant of the Big Bang. These latest results will no doubt frustrate cosmologists, because Planck has so far failed to shed much light on some of the biggest mysteries of physics, including what constitutes the dark matter and dark energy that appears to dominate the universe.

    e
    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe)

    ESA Planck
    ESA Planck schematic
    ESA/Planck

    Cosmic Background Radiation Planck
    Cosmic Background Radiation per Planck

    WMAP
    NASA/WMAP spacecraft

    Cosmic Background Radiation per WMAP
    Cosmic Background Radiation per WMAP

    Planck ran from 2009–2013, and the first data were released in March last year, comprising temperature data taken during the first 15 months of observations. A more complete data set from Planck will be published later this month, and is being previewed this week at a conference in Ferrara, Italy (Planck 2014 – The microwave sky in temperature and polarization). So far, Planck scientists have revealed that a previous disagreement of 1–1.5% between Planck and its predecessor – NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) – regarding the mission’s “absolute-temperature” measurements has been reduced to 0.3%.

    Winnowing dark matter

    Planck’s latest measurement of the CMB polarization rules out a class of dark-matter models involving particle annihilation in the early universe. These models were developed to explain excesses of cosmic-ray positrons that have been measured by three independent experiments – the PAMELA mission, the Alpha Magnetic Spectrometer and the Fermi Gamma-Ray Space Telescope.

    INFN PAMELA spacecraft
    PAMELA

    AMS-02
    AMS-02

    NASA Fermi Telescope
    NASA/Fermi

    The Planck collaboration also revealed that it has, for the first time, “detected unambiguously” traces left behind by primordial neutrinos on the CMB. Such neutrinos are thought to have been released one second after the Big Bang, when the universe was still opaque to light but already transparent to these elusive particles. Planck has set an upper limit (0.23 eV/c2) on the sum of the masses of the three types of neutrinos known to exist. Furthermore, the new data exclude the existence of a fourth type of neutrino that is favoured by some models.

    Planck versus BICEP2

    Despite the new data, the collaboration did not give any insights into the recent controversy surrounding the possible detection of primordial “B-mode” polarization of the CMB by astronomers working on the BICEP2 telescope.

    BICEP 2
    BICEP 2 interior
    BICEP 2 with South Pole Telescope

    If verified, the BICEP2 observation would be “smoking-gun” evidence for the rapid “inflation” of the early universe – the extremely rapid expansion that cosmologists believe the universe underwent a mere 10–35 s after the Big Bang. A new analysis of polarized dust emission in our galaxy, carried out by Planck earlier in September, showed that the part of the sky observed by BICEP2 has much more dust than originally anticipated, and while this did not completely rule out BICEP2’s original claim, it established that the dust emission is nearly as big as the entire BICEP2 signal. Both Planck and BICEP2 have since been working together on joint analysis of their data, but a result is still forthcoming.

    [THIS IS THE BEST WE CAN DO UNTIL ESA RELEASES THEIR LATEST FINDINGS FROM PLANCK]

    See the full article here.

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  • richardmitnick 9:44 pm on December 3, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From Ethan Siegel: “The Moment of Truth for BICEP2″ 

    Starts with a bang
    Starts with a Bang

    Dec 2, 2014
    Ethan Siegel

    “The paradigm of physics — with its interplay of data, theory and prediction — is the most powerful in science.” -Geoffrey West

    Earlier this year, the BICEP2 experiment shook up the world of cosmology, announcing that they had detected gravitational waves originating from before the Big Bang! Not only did they announce this, but they announced that they had done so with a signal in excess of 5σ, which is regarded as the gold standard for a detection in physics.

    BICEP 2
    BICEP 2 interior
    BICEP2 (With South Pole Telescope

    1
    Image credit: BICEP2 Collaboration — P. A. R. Ade et al, 2014 (R).

    But this may all turn out — despite the hoopla — to be absolutely nothing. Or, as it were, nothing more than a phantasm, as the observed signal may have originated from a source as mundane as our own galaxy, and have nothing to do with anything from billions of years ago!

    How did we get into this mess, and how do we get out of it? The answer to both questions is “science,” and it’s a great illustration of how the process and the body of knowledge actually evolves. Put your preconceptions of how it ought to work aside, and let’s dive in!

    2
    Image credit: ESA and the Planck Collaboration.

    This is a snapshot of the cosmic microwave background (CMB), the leftover glow from the Big Bang, as viewed by the Planck satellite. Planck has the best resolution of any all-sky map of the CMB, getting down to resolutions smaller than one tenth of a degree. The temperature fluctuations are minuscule: on the order of just a few tens of microKelvin, less than 0.01% of the actual CMB temperature.

    3
    Image credit: Wikimedia Commons user SuperManu.

    But buried in this signal is another, even more subtle one: the signal of photon polarization.

    4
    Image credit:the BICEP2 collaboration, via http://www.cfa.harvard.edu/news/2014-05.

    Basically, when photons pass through electrically charged particles in certain configurations, their polarizations — or how their electric and magnetic fields are oriented — are affected. If we look at how the two types of polarization, the E-modes and B-modes, are affected on a variety of angular scales, we ought to be able to reconstruct what caused these signals.

    2
    7
    Images credit: Amanda Yoho [Upper]; http://b-pol.org/ [Lower], of an E-mode polarization pattern at left and a B-mode pattern at right.

    A portion of this signal, in addition to charged particles, could also originate from gravitational waves created in the early Universe. There are two main classes of models of inflation that give us a Universe consistent with what we observe in all ways: new inflation, which was actually the second model (and first viable model) ever proposed, and chaotic inflation, which was the third model (and second viable one).

    9
    o
    Images credit: two inflation potentials, with chaotic inflation [Upper] and new inflation [Lower] shown. Chaotic inflation generates very large gravitational waves, while new inflation generates tiny ones. Generated by me, using google graph.

    These two models of inflation make vastly different predictions for gravitational radiation: new inflation predicts gravitational waves (and primordial B-modes) that are extraordinarily tiny, and well beyond the reach of any current or even planned experiment or observatory, while chaotic inflation predicts huge B-modes, some of the largest ones allowable. These signatures have a characteristic frequency spectrum and affect all wavelengths of light identically, so it should be an easy signal to find if our equipment is sensitive to it.

    And that’s where BICEP2 comes in.

    y
    Image credit: Sky and Telescope / Gregg Dinderman, via http://www.skyandtelescope.com/news/First-Direct-Evidence-of-Big-Bang-Inflation-250681381.html.

    Rather than measuring the whole sky, BICEP2 measured just a tiny fraction of the sky — about three fingers held together at arm’s length worth — but were able to tease out both the E-mode and B-mode polarization signals. And based on their analysis of the B-modes, which was very careful and very good, mind you, they claimed the greater-than-5σ detection.

    What this means is that they had enough data so that the odds that what they were seeing was a “fluke” of having observed just a serendipitous patch of sky was tiny, or a one in 1.7 million chance. Flukes happen all the time at the one-in-100 level or the one-in-1,000, but one-in-1.7 million flukes… well, let’s just say you don’t win the lotto jackpot very often.

    But there’s another type of error that they didn’t report. Not a statistical error, which is the kind you can improve on by taking more data, but a systematic error, which could be an effect that causes what you think is your signal, but is actually due to some other source! This type of error normally goes undetected because if you knew about it you’d account for it!

    This is exactly what happened a couple of years ago, if you remember the “faster-than-light-neutrino” business. An experiment at CERN had reported the early arrival by just a few nanoseconds of thousands upon thousands of neutrinos, meaning that they would have exceeded the speed of light by something like 0.003%, a small but meaningful amount. As it turned out, the neutrinos weren’t arriving early; there was a loose cable that accounted for the error!

    f
    Image credit: ESA / Planck Collaboration, via http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1101_planck/news1101_planck-en-print.html.

    Well, one of the things the BICEP2 team didn’t measure was the galactic foreground emission. Polarized light — including light that contains these B-modes — gets emitted by the Milky Way galaxy, and that can contaminate your signal. The BICEP2 team used a very clever trick to try and eliminate this, by interpolating unreleased Planck data about galactic foregrounds, but when the Planck team actually released their data, the foregrounds were significantly different from what BICEP2 had anticipated. And with the new Planck data, the announcement of a “discovery” needed to be walked back; the evidence was now something like a one-in-200 chance of being a fluke.

    l
    Image credit: John Kovac, viahttp://cosmo2014.uchicago.edu/depot/invited-talk-kovac-john.pdf.

    In other words, although gravitational waves could have caused this signal, so could other, far more mundane sources, including just our boring old galaxy!

    Sometime later this month, the Planck team will release their all-sky polarization results, and either at that moment or shortly thereafter, we’ll find out whether there really are gravitational waves from inflation that can be detected with our current generation of telescopes, satellites and observatories. We’ll find out whether chaotic inflation is right, or whether we need to keep searching for the gravitational wave signal from before the Big Bang. We already have the density fluctuation signal, so we can be confident that inflation happened. It’s just a question of which type.

    n
    Image credit: Bock et al. (2006, astro-ph/0604101); modifications by me.

    Stay curious, stay hungry for more knowledge, but always demand that your scientific claims be independently verified, that your possible systematic errors be checked, and that you have overwhelming evidence before believing the extraordinary claims. It’s easy to make a bold statement; it’s hard to start a bona fide scientific revolution!

    See the full article here.

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  • richardmitnick 7:12 pm on October 21, 2014 Permalink | Reply
    Tags: , , , BICEP2, ,   

    From Daily Galaxy: “Astrophysicists Using Big Bang’s Primordial Light to Probe Largest Structures in the Universe” 

    Daily Galaxy
    The Daily Galaxy

    October 21, 2014
    The Daily Galaxy via University of California – Berkeley

    An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, determine the masses of neutrinos and perhaps uncover some of the mysteries of dark matter and dark energy. The POLARBEAR team is measuring the polarization of light that dates from an era 380,000 years after the Big Bang, when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy density a trillion times higher than what they are producing at the CERN collider.

    Cosmic Background Radiation Planck
    CMB per Planck

    The Large Hadron Collider near Geneva is trying to simulate that early era by slamming together beams of protons to create a hot dense soup from which researchers hope new particles will emerge, such as the newly discovered Higgs boson. But observing the early universe, as the POLARBEAR group does may also yield evidence that new physics and new particles exist at ultra-high energies.

    The team uses these primordial photon’s light to probe large-scale gravitational structures in the universe, such as clusters or walls of galaxies that have grown from what initially were tiny fluctuations in the density of the universe. These structures bend the trajectories of microwave background photons through gravitational lensing, distorting its polarization and converting E-modes into B-modes. POLARBEAR images the lensing-generated B-modes to shed light on the intervening universe.

    In a paper published this week in the Astrophysical Journal, the POLARBEAR consortium, led by University of California, Berkeley, physicist Adrian Lee, describes the first successful isolation of a “B-mode” produced by gravitational lensing in the polarization of the cosmic microwave background radiation.

    Polarization is the orientation of the microwave’s electric field, which can be twisted into a “B-mode” pattern as the light passes through the gravitational fields of massive objects, such as clusters of galaxies.

    lens

    “We made the first demonstration that you can isolate a pure gravitational lensing B-mode on the sky,” said Lee, POLARBEAR principal investigator, UC Berkeley professor of physics and faculty scientist at Lawrence Berkeley National Laboratory (LBNL). “Also, we have shown you can measure the basic signal that will enable very sensitive searches for neutrino mass and the evolution of dark energy.”

    The POLARBEAR team, which uses microwave detectors mounted on the Huan Tran Telescope in Chile’s Atacama Desert, consists of more than 70 researchers from around the world. They submitted their new paper to the journal one week before the surprising March 17 announcement by a rival group, the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) experiment, that they had found the holy grail of microwave background research. That team reported finding the signature of cosmic inflation – a rapid ballooning of the universe when it was a fraction of a fraction of a second old – in the polarization pattern of the microwave background radiation.

    Huan Tran Telescope
    Huan Tran Telescope (Kavli IPMU)

    BICEP 2
    BICEP2 with South Pole Telescope

    Subsequent observations, such as those announced last month by the Planck satellite, have since thrown cold water on the BICEP2 results, suggesting that they did not detect what they claimed to detect.

    While POLARBEAR may eventually confirm or refute the BICEP2 results, so far it has focused on interpreting the polarization pattern of the microwave background to map the distribution of matter back in time to the universe’s inflationary period, 380,000 years after the Big Bang.

    POLARBEAR’s approach, which is different from that used by BICEP2, may allow the group to determine when dark energy, the mysterious force accelerating the expansion of the universe, began to dominate and overwhelm gravity, which throughout most of cosmic history slowed the expansion.

    BICEP2 and POLARBEAR both were designed to measure the pattern of B-mode polarization, that is, the angle of polarization at each point in an area of sky. BICEP2, based at the South Pole, can only measure variation over large angular scales, which is where theorists predicted they would find the signature of gravitational waves created during the universe’s infancy. Gravitational waves could only have been created by a brief and very rapid expansion, or inflation, of the universe 10-34 seconds after the Big Bang.

    In contrast, POLARBEAR was designed to measure the polarization at both large and small angular scales. Since first taking data in 2012, the team focused on small angular scales, and their new paper shows that they can measure B-mode polarization and use it to reconstruct the total mass lying along the line of sight of each photon.

    The polarization of the microwave background records minute density differences from that early era. After the Big Bang, 13.8 billion years ago, the universe was so hot and dense that light bounced endlessly from one particle to another, scattering from and ionizing any atoms that formed. Only when the universe was 380,000 years old was it sufficiently cool to allow an electron and a proton to form a stable hydrogen atom without being immediately broken apart. Suddenly, all the light particles – called photons – were set free.

    “The photons go from bouncing around like balls in a pinball machine to flying straight and basically allowing us to take a picture of the universe from only 380,000 years after the Big Bang,” Lee said. “The universe was a lot simpler then: mainly hydrogen plasma and dark matter.”

    These photons, which, today, have cooled to a mere 3 degrees Kelvin above absolute zero, still retain information about their last interaction with matter. Specifically, the flow of matter due to density fluctuations where the photon last scattered gave that photon a certain polarization (called E-mode polarization).

    “Think of it like this: the photons are bouncing off the electrons, and there is basically a last kiss, they touch the last electron and then they go for 14 billion years until they get to telescopes on the ground,” Lee said. “That last kiss is polarizing.”

    While E-mode polarization contains some information, B-mode polarization contains more, because photons carry this only if matter around the last point of scattering was unevenly or asymmetrically distributed. Specifically, the gravitational waves created during inflation squeezed space and imparted a B-mode polarization that BICEP2 may have detected. POLARBEAR, on the other hand, has detected B-modes that are produced by distortion of the E-modes by gravitational lensing.

    While many scientists suspected that the gravitational-wave B-mode polarization might be too faint to detect easily, the BICEP2 team, led by astronomers at Harvard University’s Center for Astrophysics, reported a large signal that fit predictions of gravitational waves. Current doubt about this result centers on whether or not they took into account the emission of dust from the galaxy that would alter the polarization pattern.

    In addition, BICEP2’s ability to measure inflation at smaller angular scales is contaminated by the gravitational lensing B-mode signal.

    “POLARBEAR’s strong suit is that it also has high angular resolution where we can image this lensing and subtract it out of the inflationary signal to clean it up,” Lee said.

    Two other papers describing related results from POLARBEAR were accepted in the spring by Physical Review Letters.

    One of those papers is about correlating E-mode polarization with B-mode polarization, which “is the most sensitive channel to cosmology; that’s how you can measure neutrino masses, how you might look for early behavior of dark energy,” Lee said.

    The [basically blue] image [above] shows the scale of a large quasar group” (LQG), the largest structure ever seen in the entire universe that runs counter to our current understanding of the scale of the universe. Even traveling at the speed of light, it would take 4 billion years to cross. This is significant not just because of its size but also because it challenges the Cosmological Principle, which has been widely accepted since [Albert] Einstein, the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.

    See the full article here.

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  • richardmitnick 2:02 pm on September 22, 2014 Permalink | Reply
    Tags: , , , , BICEP2, , ,   

    From Symmetry: “Cosmic dust proves prevalent” 

    Symmetry

    September 22, 2014
    Kathryn Jepsen

    Space dust accounts for at least some of the possible signal of cosmic inflation the BICEP2 experiment announced in March. How much remains to be seen.

    Space is full of dust, according to a new analysis from the European Space Agency’s Planck experiment.

    planck

    That includes the area of space studied by the BICEP2 experiment, which in March announced seeing a faint pattern left over from the big bang that could tell us about the first moments after the birth of the universe.

    gwb
    Gravitational Wave Background from BICEP2

    The Planck analysis, which started before March, was not meant as a direct check of the BICEP2 result. It does, however, reveal that the level of dust in the area BICEP2 scientists studied is both significant and higher than they thought.

    “There is still a wide range of possibilities left open,” writes astronomer Jan Tauber, ESA project scientist for Planck, in an email. “It could be that all of the signal is due to dust; but part of the signal could certainly be due to primordial gravitational waves.”

    BICEP2 scientists study the cosmic microwave background, a uniform bath of radiation permeating the universe that formed when the universe first cooled enough after the big bang to be transparent to light. BICEP2 scientists found a pattern within the cosmic microwave background, one that would indicate that not long after the big bang, the universe went through a period of exponential expansion called cosmic inflation. The BICEP2 result was announced as the first direct evidence of this process.

    The problem is that the same pattern, called B-mode polarization, also appears in space dust. The BICEP2 team subtracted the then known influence of the dust from their result. But based on today’s Planck result, they didn’t manage to scrub all of it.

    How much the dust influenced the BICEP2 result remains to be seen.

    In November, Planck scientists will release their own analysis of B-mode polarization in the cosmic microwave background, in addition to a joint analysis with BICEP2 specifically intended to check the BICEP2 result. These results could answer the question of whether BICEP2 really saw evidence of cosmic inflation.

    “While we can say the dust level is significant,” writes BICEP2 co-leader Jamie Bock of Caltech and NASA’s Jet Propulsion Laboratory, “we really need to wait for the joint BICEP2-Planck paper that is coming out in the fall to get the full answer.”

    [Me? I am rooting for my homey, Alan Guth, from Highland Park, NJ, USA]

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 11:18 am on July 11, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , South Pole Telescope   

    From BBC- “Cosmic inflation: BICEP2 and Planck to share data” 

    BBC

    3 July 2014
    Jonathan Amos

    spt
    The BICEP2 telescope studied a small patch of sky in detail above the South Pole

    Scientists on rival projects looking for evidence that the early Universe underwent a super-expansion are in discussion about working together.

    The negotiations between the US-led BICEP2 group and Europe’s Planck Collaboration are at an early stage.

    BICEP2 announced in March that its South Pole telescope had found good evidence for “cosmic inflation“.

    South Pole Telescope
    South Pole Telescope

    Cosmic Background Radiation Planck
    CMB from Planck

    But to be sure, it needs the best data on factors that confound its research – data that Planck has been compiling.

    If the two teams come to an arrangement, it is more likely they will hammer down the uncertainties.

    “We’re still discussing the details but the idea is to exchange data between the two teams and eventually come out with a joint paper,” Dr Jan Tauber, the project scientist on the European Space Agency’s Planck satellite, told BBC News.

    This paper, hopefully, would be published towards the end of the year, he added.

    dust
    Foreground dust per Planck

    The question of whether the BICEP2 team did, or did not, identify a signal on the sky for inflation has gripped the science world for weeks.

    The group used an extremely sensitive detector in its Antarctic telescope to study light coming to Earth from the very edge of the observable Universe – the famous Cosmic Microwave Background (CMB) radiation.
    Planck artist impression The Planck satellite was launched in 2009 to map the Cosmic Microwave Background

    BICEP2 looked for swirls in the polarisation of the light.

    This pattern in the CMB’s directional quality is a fundamental prediction of inflation – the idea that there was an ultra-rapid expansion of space just fractions of a second after the Big Bang.

    The twists, known as B-modes, are an imprint of the waves of gravitational energy that would have accompanied the violent growth spurt.

    But this primordial signal – if it exists – is expected to be extremely delicate, and a number of independent scientists have expressed doubts about the American team’s finding. And the BICEP2 researchers themselves lowered their confidence in the detection when they formally published their work in a Physical Review Letters paper last month.

    At issue is the role played by foreground dust in our galaxy.

    Nearby spinning grains can produce an identical polarisation pattern, and this effect must be removed to get an unambiguous view of the primordial, background signal.

    The BICEP2 team used every piece of dust information it could source on the part of the sky it was observing above Antarctica.

    What it lacked, however, was access to the dust data being compiled by the Planck space telescope, which has mapped the microwave sky at many more frequencies than BICEP2.

    This allows it to more easily characterise the dust and discern its confounding effects.
    Dust Planck released dust information close to the galactic plane in May

    In May, the Planck Collaboration published dust polarisation information gathered close to the galaxy’s centre – where the grains are most abundant.

    In a few weeks’ time, the Planck team plans to release further information detailing galactic dust in high latitude regions, including the narrow patch of the southern sky examined by BICEP2.

    And then, in late October, the Planck Collaboration is expected to say something about whether it can detect primordial B-modes.

    As Dr Tauber explained, Planck’s approach to the problem is a different one to BICEP2’s.

    “Planck’s constraints on primordial B-modes will come from looking at the whole sky with relatively low sensitivity as compared to BICEP2,” he said.

    “But because we can look at the whole sky, it makes up for some of that [lower sensitivity] at least. On the other hand, we have to deal with the foregrounds – we can’t ignore them at all.

    “At the same time, we will work together with BICEP2 so that we can contribute our data to improve the overall assessment of foregrounds and the Cosmic Microwave Background.

    “We hope to start working with them very soon, and if all goes well then we can maybe publish in the same timeframe as our main result [at the end of October].”

    See the full article here.


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  • richardmitnick 12:12 pm on June 24, 2014 Permalink | Reply
    Tags: , , , BICEP2, , , , ,   

    From SLAC Lab: “SLAC, Stanford Scientists Play Key Roles in Confirming Cosmic Inflation” 


    SLAC Lab

    March 19, 2014
    Glennda Chui

    Chao-Lin Kuo and Kent Irwin Helped Develop Technology for Imaging Gravitational Waves

    Two scientists at Stanford University and SLAC National Accelerator Laboratory made key contributions to the discovery of the first direct evidence for cosmic inflation – the rapid expansion of the infant universe in the first trillionth of a trillionth of a trillionth of a second after the Big Bang.

    Chao-Lin Kuo is one of four co-leaders of the BICEP2 collaboration that announced the discovery on Monday. An assistant professor at SLAC and Stanford, he led the development of the BICEP2 detector and is building the BICEP3 follow-on experiment in his Stanford lab for deployment at the South Pole later this year.

    ck
    Chao-Lin Kuo at the South Pole research station where the BICEP2 experiment operated from 2010 to 2012. (Photo courtesy of Chao-Lin Kuo)

    BICEP 2
    BICEP With South Pole Telescope

    Kent Irwin invented the type of sensor used in BICEP2 as a graduate student at Stanford, adapted it for X-ray experiments and studies of the cosmos during a 20-year career at the National Institute for Standards and Technology, and returned to SLAC and Stanford as a professor in September to lead a major initiative in sensor development.

    ki
    Kent Irwin (Matt Beardsley/SLAC)

    Both are members of the Kavli Institute for Particle Physics and Astrophysics (KIPAC), which is jointly run by SLAC and Stanford.

    “It’s exciting that the same technology I developed as a grad student to search for tiny particles of dark matter is also being used to do research on the scale of the universe and to study the practical world of batteries, materials and biology in between,” Irwin said. His group is working toward installing a version of the BICEP2 sensors at SLAC’s X-ray light sources – Stanford Synchrotron Radiation Lightsource (SSRL) and Linac Coherent Light Source (LCLS) – as well as at a planned LCLS upgrade.

    Searching for Ripples in Space-time

    BICEP is a series of experiments that began operating at the South Pole in January 2006, taking advantage of the cold, clear, dry conditions to look for a faint, swirling polarization of light in the Cosmic Microwave Background (CMB) radiation. The light in the CMB dates back to 380,000 years after the Big Bang; before that, the early universe was opaque and no light could get through.

    Cosmic Background Radiation Planck
    CMB Planck

    But some theories predicted that gravitational waves – ripples in space-time – would have been released in the first tiny fraction of a second after the Big Bang, as the universe expanded exponentially in what is known as “cosmic inflation.” If that were the case, scientists might be able to detect the imprint of those waves in the form of a slight swirling pattern known as “B-mode polarization” in the CMB.

    On Monday, researchers from the BICEP2 experiment, which ran from January 2010 through December 2012, announced that they had found that smoking-gun signature, confirming the rapid inflation that had been theorized more than 30 years ago by Alan Guth and later modified by Andrei Linde, a Russian theorist who is now at Stanford.

    Building a Better Detector

    Kuo started working on BICEP1 as a postdoctoral researcher at Caltech in 2003. The circuitry in the experiment’s detectors was all made by hand. For the next-generation detector, BICEP2, the collaborating scientists wanted something that could be mass-produced in larger quantities, allowing them to pack more sensors into the array and collect data 10 times faster. So Kuo also started designing that technology, which used photolithography – a standard tool for making computer chips – to print sensors onto high-resolution circuit boards.

    sunset
    The sun sets behind BICEP2 (in the foreground) and the South Pole Telescope (in the background). (Steffen Richter, Harvard University)

    b2
    The BICEP2 detector shown in this electron-beam micrograph works by converting the light from the cosmic microwave background into heat. A titanium film tuned on its transition to a superconducting state makes a sensitive thermometer to measure this heat. The sensors are cooled to just 0.25 degrees above absolute zero to minimize thermal noise. (Anthony Turner, JPL)

    In 2008 Kuo arrived at SLAC and Stanford and began working on the next-generation experiment, BICEP3, for which he is principal investigator. Scheduled for deployment at the South Pole later this year, BICEP3 will look at a larger patch of the sky and collect data 10 times faster than its predecessor; it’s also more sensitive and more compact.

    SLAC took on a bigger role in this research in October 2013 by awarding up to $2 million in Laboratory Directed Research and Development funding over three years for the “KIPAC Initiative for Cosmic Inflation,” with Kuo as principal investigator. The grant establishes a large-scale Cosmic Microwave Background program at the lab, with part of the funding going toward BICEP3, and has a goal of establishing KIPAC as a premier institute for the study of cosmic inflation. There are also plans to establish a comprehensive development, integration, and testing center at SLAC for technologies to further explore the CMB, which holds clues not only to gravitational waves and cosmic inflation but also to dark matter, dark energy and the nature of the neutrino.

    A Fancy Thermometer for Tiny Signals

    Kent Irwin entered the picture in the early 1990s, while a graduate student in the laboratory of Stanford/SLAC Professor Blas Cabrera. There he invented the superconducting Transition Edge Sensor, or TES, for the Cryogenic Dark Matter Search, which is trying to detect incoming particles of dark matter in a former iron mine in Minnesota. When he moved to NIST, he and his team adapted the technology for other uses and also developed a very sensitive way to read out the signal from the sensors with devices known as SQUID multiplexers.

    Printing TES devices on circuit boards and using the SQUID multiplexers to read them out made it possible to create large TES arrays and greatly expanded their applications in astronomy, nuclear non-proliferation, materials analysis and homeland defense. It was also the key factor in allowing the BICEP team to expand the number of detectors in its experiments from 98 in BICEP1 to 500 in BICEP2, and opens the path to even larger arrays that will greatly increase the sensitivity of future experiments.

    A TES is “basically a very fancy thermometer,” Irwin says. “We’re measuring the power coming from the CMB.” The TES receives a microwave signal from an antenna and translates it into heat; the heat then warms a piece of metal that’s chilled to the point where it hovers on the edge of being superconducting – conducting electricity with 100 percent efficiency and no resistance. When a material is at this edge, a tiny bit of incoming heat causes a disproportionately large change in resistance, giving scientists a very sensitive way to measure small temperature changes. The TES devices for BICEP2 were built at NASA’s Jet Propulsion Laboratory, and Irwin’s team at NIST made the SQUID multiplexers.

    The Road Ahead

    Looking ahead, CMB researchers in the United States developed a roadmap leading to a fourth-generation experiment as part of last year’s Snowmass Summer Study, which lays out a long-term direction for the national high energy physics research program. That experiment would deploy hundreds of thousands of detector sensors and stare at a much broader swath of the cosmos at an estimated cost of roughly $100 million.

    “These are incredibly exciting times, with theory, technology and experiment working hand in hand to give us an increasingly clear picture of the very first moments of the universe,” said SLAC Lab Director Chi-Chang Kao. “I want to congratulate everyone in the many collaborating institutions who made this spectacular result possible. We at SLAC are looking forward to continuing to invest and work in this area as part of our robust cosmology program.”

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 12:22 pm on April 23, 2014 Permalink | Reply
    Tags: , , , BICEP2,   

    From Symmetry: “A ‘crack in the cosmic egg'” 

    Symmetry

    April 23, 2014
    This article is based on a Kavli Foundation press release.

    Last month, scientists on the BICEP2 experiment announced the first hard evidence for cosmic inflation, the process by which the infant universe swelled from microscopic to cosmic size in an instant.

    BICEP 2
    BICEP2 and the South Pole Telescope

    Scientists have thought for more than three decades that we might someday find such a signal, so the discovery was not entirely unexpected. What was unexpected, however, was just how strong the signal turned out to be.

    “The theoretical community is abuzz,” theorist Michael Turner, director of the Kavli Institute for Cosmological Physics and a University of Chicago professor, said in a recent discussion. “We got the signal we were looking for—that’s good—but we shouldn’t have gotten one according to the highbrow theorists because they say it should be too small. So we got a surprise. And often in science, that’s the case. We like to the experimenters to find what we predict, but we also like surprises.”

    The BICEP2 experiment—the second generation of the Background Imaging of Cosmic Extragalactic Polarization experiment—consists of a telescope at the South Pole (pictured above, on left) built to look back to the universe’s first light.

    Turner moderated a conversation, broadcast as a Google+ Hangout, about the result with BICEP2 postdoctoral researcher Walter Ogburn of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University; KICP Deputy Director John Carlstrom, who leads two other experiments that study the early universe; and BICEP2 physicist Abigail Vieregg, a professor at the University of Chicago and KICP.

    The BICEP2 surprise is still so new that additional implications keep coming to light each week. It’s already clear that the result rules out many theoretical models of inflation—most of them, in fact—because they predict a signal much weaker than the one detected. In addition, the discovery also seems to disprove a theory that says that the universe expands, collapses and expands again in an ongoing cycle.

    “It’s a funny thing when you’re on the inside of a discovery like this,” Vieregg said during the Google+ Hangout. “It’s only when you release the results to the world and watch the reaction of the community that, at least for me, it really hits home how important it is. If this is what we think it is, it’s a very big deal.”

    Turner said the result could very well be a “crack in the cosmic egg,” offering clues that even the most accepted theoretical assumptions contain inaccuracies.

    “Maybe we need to… allow some new physics in there,” Carlstrom said. “Maybe there are more neutrinos. Maybe they’re more massive than we thought. Or maybe it’s something none of us have thought of yet.”

    Theorists will carefully consider these ideas and their implications over the coming months and years. Meanwhile, the signal still needs to be experimentally confirmed.

    Results from other telescopes, including the Planck satellite and the South Pole Telescope, are expected in the coming year. After that, the next step will be to measure the signal’s intricacies, searching for evidence of how inflation started and how exactly the universe worked in its high-energy infancy. Those results, in turn, may shed light on some of our biggest questions about how the universe began and how the forces of nature are unified.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 12:15 pm on March 25, 2014 Permalink | Reply
    Tags: , , , , , , BICEP2   

    From Berkeley Lab: “Setting a Trap for Gravity Waves” 


    Berkeley Lab

    March 18, 2014
    Paul Preuss paul_preuss@lbl.gov

    In 1996 Uros Seljak was a postdoc at Harvard, contemplating ways to extract information from the cosmic microwave background (CMB). The distribution of anisotropies, slight temperature differences, in the CMB had much to say about the large-scale structure of the universe. If it were also possible to detect the polarization of the CMB itself, however, a much wider window would be opened – polarization could even reveal the tracks of gravitational waves.

    Cosmic Background RadiationXMM Newton
    CMB from ESA/Planck

    Gravitational waves are distortions of space on a small scale, and have no consequence for the large-scale structure of the universe,” says Seljak, now a professor of physics and astronomy at UC Berkeley and a faculty scientist in Berkeley Lab’s Physics Division. “Both result from perturbations during inflation, but the seeds of large-scale structure are described by a scalar field, and gravitational waves by a tensor field.”

    Cosmologists already assumed that inflation theory was essentially correct: virtually instantaneous expansion after the big bang explained how regions of the universe never otherwise in contact had in fact started from the same initial conditions. Here was a way to test inflation directly.

    Seljak posted a paper to arXiv (soon published in the Astrophysical Journal), becoming the first to predict how polarization could be used to find CMB tensor signals, including gravitational waves. Marc Kamionkowski, Arthur Kosowsky, and Albert Stebbins of Fermilab independently posted their similar proposal shortly thereafter. In further work with Matias Zaldarriaga, Seljak named the E and B modes of CMB polarization, borrowing the symbols for light’s electric and magnetic fields – scalar fields produce E-mode polarization; a gravitational tensor field can produce both.

    Fast forward to the year 2000, when Adrian Lee, a professor of astrophysics at UC Berkeley and faculty scientist in the Lab’s Physics Division, came up with the idea of suspending the recently invented transition-edge sensor bolometer(TES), creating what he describes as “a trampoline that heats up when an energy pulse lands on it” – the more energy, the bigger the reaction.

    Lee integrated suspended TESs with other functions in flat chips suitable for the focal planes of CMB telescopes. He proposed just such a telescope, the POLARBEAR experiment, initiated with support from Berkeley Lab’s Laboratory Directed Research and Development (LDRD). BICEP2 and many other CMB telescopes also use versions of these focal-plane chips.

    BICEP 2
    BICEP2 at the South Pole Telescope

    On Monday, March 17, 2014, the BICEP2 collaboration grabbed the brass ring: first detection of B-mode polarization from gravitational waves, thus first direct evidence of inflation – a signal far stronger than most scientists had expected.

    “We look forward to working with BICEP2 to refine their measurements,” says Lee. “Until now, the best evidence for inflation was a slight ‘tilt’ in the CMB scalar field. POLARBEAR’s higher resolution could detect a similar tilt in the tensor field, a double confirmation of inflation.”

    Among the many implications of the large B-mode signal, says Seljak: “It may force us in the direction of string theory. It also fits in with models of continuing inflation that produce multiple universes.”

    Berkeley Lab has played an important part in opening the cosmic frontier to even wider vistas.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal


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