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  • richardmitnick 2:58 pm on April 11, 2017 Permalink | Reply
    Tags: Antimatter, , Brookhaven, ,   

    From Symmetry: “What’s left to learn about antimatter?” 

    Symmetry Mag

    Symmetry

    04/11/17
    Sarah Charley

    1
    BBC Focus Magazine

    What do shrimp, tennis balls and pulsars all have in common? They are all made from matter.

    Admittedly, that answer is a cop-out, but it highlights a big, persistent quandary for scientists: Why is everything made from matter when there is a perfectly good substitute—antimatter?

    The European laboratory CERN hosts several experiments to ascertain the properties of antimatter particles, which almost never survive in our matter-dominated world.

    Particles (such as the proton and electron) have oppositely charged antimatter doppelgangers (such as the antiproton and antielectron). Because they are opposite but equal, a matter particle and its antimatter partner annihilate when they meet.

    Antimatter wasn’t always rare. Theoretical and experimental research suggests that there was an equal amount of matter and antimatter right after the birth of our universe. But 13.8 billion years later, only matter-made structures remain in the visible universe.

    Scientists have found small differences between the behavior of matter and antimatter particles, but not enough to explain the imbalance that led antimatter to disappear while matter perseveres. Experiments at CERN are working to solve that riddle using three different strategies.

    3
    No image caption. No image credit. http://www.projectrho.com/public_html/rocket/antimatterfuel.php

    Antimatter under the microscope

    It’s well known that CERN is home to Large Hadron Collider, the world’s highest-energy particle accelerator. Less known is that CERN also hosts the world’s most powerful particle decelerator—a machine that slows down antiparticles to a near standstill.

    4
    Paving the way for a new antimatter experiment. The GBAR experiment will create antihydrogen ions at rest to study the action of gravity upon antimatter. 13 March 2017 | Author Iva Raynova | Tagged antimatter, ELENA, Antiproton Decelerator, gravity

    The antiproton decelerator is fed by CERN’s accelerator complex. A beam of energetic protons is diverted from CERN’s Proton Synchrotron and into a metal wall, spawning a multitude of new particles, including some antiprotons. The antiprotons are focused into a particle beam and slowed by electric fields inside the antiproton decelerator. From here they are fed into various antimatter experiments, which trap the antiprotons inside powerful magnetic fields.

    “All these experiments are trying to find differences between matter and antimatter that are not predicted by theory,” says Will Bertsche, a researcher at University of Manchester, who works in CERN’s antimatter factory. “We’re all trying to address the big question: Why is the universe made up of matter these days and not antimatter?”

    By cooling and trapping antimatter, scientists can intimately examine its properties without worrying that their particles will spontaneously encounter a matter companion and disappear. Some of the traps can preserve antiprotons for more than a year. Scientists can also combine antiprotons with positrons (antielectrons) to make antihydrogen.

    “Antihydrogen is fascinating because it lets us see how antimatter interacts with itself,” Bertsche says. “We’re getting a glimpse at how a mirror antimatter universe would behave.”

    Scientists in CERN’s antimatter factory have measured the mass, charge, light spectrum, and magnetic properties of antiprotons and antihydrogen to high precision. They also look at how antihydrogen atoms are affected by gravity; that is, do the anti-atoms fall up or down? One experiment is even trying to make an assortment of matter-antimatter hybrids, such as a helium atom in which one of the electrons is replaced with an orbiting antiproton.

    So far, all their measurements of trapped antimatter match the theory: Except for the opposite charge and spin, antimatter appears completely identical to matter. But these affirmative results don’t deter Bertsche from looking for antimatter surprises. There must be unpredicted disparities between these particle twins that can explain why matter won its battle with antimatter in the early universe.

    “There’s something missing in this model,” Bertsche says. “And nobody is sure what that is.”

    Antimatter in motion

    The LHCb experiment wants to answer this same question, but they are looking at antimatter particles that are not trapped.

    CERN/LHCb

    Instead, LHCb scientists study how free-range antimatter particles behave as they travel and transform inside the detector.

    “We’re recording how unstable matter and antimatter particles decay into showers of particles and the patterns they leave behind when they do,” says Sheldon Stone, a professor at Syracuse University working on the LHCb Experiment. “We can’t make these measurements if the particles aren’t moving.”

    The particles-in-motion experiments have already observed some small differences between matter and antimatter particles. In 1964 scientists at Brookhaven National Laboratory noticed that neutral kaons (a particle containing a strange and down quark) decay into matter and antimatter particles at slightly different rates, an observation that won them the Nobel Prize in 1980.

    7
    Brookhaven. Two spectrometer magnets. No image credit

    The LHCb experiment continues this legacy, looking for even more discrepancies between the metamorphoses of matter and antimatter particles. They recently observed that the daughter particles of certain antimatter baryons (particles containing three quarks) have a slightly different spatial orientation than their matter contemporaries.

    But even with the success of uncovering these discrepancies, scientists are still very far from understanding why antimatter all but disappeared.

    “Theory tells us that we’re still off by nine orders of magnitude,” Stone says, “so we’re left asking, where is it? What is antimatter’s Achilles heel that precipitated its disappearance?”

    Antimatter in space

    Most antimatter experiments based at CERN produce antiparticles by accelerating and colliding protons. But one experiment is looking for feral antimatter freely roaming through outer space.

    The Alpha Magnetic Spectrometer is an international experiment supported by the US Department of Energy and NASA.

    AMS 02 schematic

    This particle detector was assembled at CERN and is now installed on the International Space Station, where it orbits Earth 400 kilometers above the surface. It records the momentum and trajectory of roughly a billion vagabond particles every month, including a million antimatter particles.

    Nomadic antimatter nuclei could be lonely relics from the Big Bang or the rambling residue of nuclear fusion in antimatter stars.

    But AMS searches for phenomena not explained by our current models of the cosmos. One of its missions is to look for antimatter that is so complex and robust, there is no way it could have been produced through normal particle collisions in space.

    “Most scientists accept that antimatter disappeared from our universe because it is somehow less resilient than matter,” says Mike Capell, a researcher at MIT and a deputy spokesperson of the AMS experiment. “But we’re asking, what if all the antimatter never disappeared? What if it’s still out there?”

    If an antimatter kingdom exists, astronomers expect that they would observe mass particle-annihilation fizzing and shimmering at its boundary with our matter-dominated space—which they don’t. Not yet, at least. Because our universe is so immense (and still expanding), researchers on AMS hypothesize that maybe these intersections are too dim or distant for our telescopes.

    “We already have trouble seeing deep into our universe,” Capell says. “Because we’ve never seen a domain where matter meets antimatter, we don’t know what it would look like.”

    AMS has been collecting data for six years. From about 100 billion cosmic rays, they’ve identified a few strange events with characteristics of antihelium. Because the sample is so tiny, it’s impossible to say whether these anomalous events are the first messengers from an antimatter galaxy or simply part of the chaotic background.

    “It’s an exciting result,” Capell says. “However, we remain skeptical. We need data from many more cosmic rays before we can determine the identities of these anomalous particles.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:12 pm on January 31, 2017 Permalink | Reply
    Tags: Antimatter, , , , , , ,   

    From Symmetry: “Sign of a long-sought asymmetry” 

    Symmetry Mag
    Symmetry

    01/30/17
    Sarah Charley

    A result from the LHCb experiment shows what could be the first evidence of matter and antimatter baryons behaving differently.

    1
    Simona Lippi

    CERN LHC LHCb
    LHCb

    A new result from the LHCb experiment at CERN could help explain why our universe is made of matter and not antimatter.

    Matter particles, such as protons and electrons, all have an antimatter twin. These antimatter twins appear identical in nearly every respect except that their electric and magnetic properties are opposite.

    Cosmologists predict that the Big Bang produced an equal amount of matter and antimatter, which is a conundrum because matter and antimatter annihilate into pure energy when they come into contact. Particle physicists are looking for any minuscule differences between matter and antimatter, which might explain why our universe contains planets and stars and not a sizzling broth of light and energy instead.

    The Large Hadron Collider doesn’t just generate Higgs bosons during its high-energy proton collisions—it also produces antimatter. By comparing the decay patterns of matter particles with their antimatter twins, the LHCb experiment is looking for miniscule differences in how these rival particles behave.

    “Many antimatter experiments study particles in a very confined and controlled environment,” says Nicola Neri, a researcher at Italian research institute INFN and one of the leaders of the study. “In our experiment, the antiparticles flow and decay, so we can examine other properties, such as the momenta and trajectories of their decay products.”

    The result, published today in Nature Physics, examined the decay products of matter and antimatter baryons (a particles containing three quarks) and looked at the spatial distribution of the resulting daughter particles within the detector. Specifically, Neri and his colleagues looked for a very rare decay of the lambda-b particle (which contains an up quark, down quark and bottom quark) into a proton and three pions (which contain an up quark and anti-down quark).

    Based on data from 6000 decays, Neri and his team found a difference in the spatial orientation of the daughter particles of the matter and antimatter lambda-bs.

    “This is the first time we’ve seen evidence of matter and antimatter baryons behaving differently,” Neri says. “But we need more data before we can make a definitive claim.”

    Statistically, the result has a significant of 3.3 sigma, which means its chances of being a just a statistical fluctuation (and not a new property of nature) is one out of a thousand. The traditional threshold for discovery is 5 sigma, which equates to odds of one out of more than a million.

    For Neri, this result is more than early evidence of a never before seen process—it is a key that opens new research opportunities for LHCb physicists.

    “We proved that we are there,” Neri says, “Our experiment is so sensitive that we can start systematically looking for this matter-antimatter asymmetry in heavy baryons at LHCb. We have this capability, and we will be able to do even more after the detector is upgraded next year.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:53 pm on January 19, 2017 Permalink | Reply
    Tags: , Antimatter, , , , ,   

    From Symmetry: “Matter-antimatter mystery remains unsolved” 

    Symmetry Mag
    Symmetry

    01/19/17
    Sarah Charley

    1
    Maximilien Brice, CERN

    Measuring with high precision, physicists at CERN found a property of antiprotons perfectly mirrored that of protons.

    There is little wiggle room for disparities between matter and antimatter protons, according to a new study published by the BASE experiment at CERN.

    cern-base-collaboartion-bloc

    Charged matter particles, such as protons and electrons, all have an antimatter counterpart. These antiparticles appear identical in every respect to their matter siblings, but they have an opposite charge and an opposite magnetic property. This recalcitrant parity is a head-scratcher for cosmologists who want to know why matter triumphed over antimatter in the early universe.

    “We’re looking for hints,” says Stefan Ulmer, spokesperson of the BASE collaboration. “If we find a slight difference between matter and antimatter particles, it won’t tell us why the universe is made of matter and not antimatter, but it would be an important clue.”

    Ulmer and his colleagues working on the BASE experiment at CERN closely scrutinize the properties of antiprotons to look for any miniscule divergences from protons. In a paper published today in the journal Nature Communications, the BASE collaboration at CERN reports the most precise measurement ever made of the magnetic moment of the antiproton.

    “Each spin-carrying charged particle is like a small magnet,” Ulmer says. “The magnetic moment is a fundamental property which tells us the strength of that magnet.”

    The BASE measurement shows that the magnetic moments of the proton and antiproton are identical, apart from their opposite signs, within the experimental uncertainty of 0.8 parts per million. The result improves the precision of the previous best measurement by the ATRAP collaboration in 2013, also at CERN, by a factor of six. This new measurement shows an almost perfect symmetry between matter and antimatter particles, thus further constricting leeway for incongruencies which might have explained the cosmic asymmetry between matter and antimatter.

    The measurement was made at the Antimatter Factory at CERN, which generates antiprotons by first crashing normal protons into a target and then focusing and slowing the resulting antimatter particles using the Antiproton Decelerator. Because matter and antimatter annihilate upon contact, the BASE experiment first traps antiprotons in a vacuum using sophisticated electromagnetics and then cools them to about 1 degree Celsius above absolute zero. These electromagnetic reservoirs can store antiparticles for long periods of time; in some cases, over a year. Once in the reservoir, the antiprotons are fed one-by-one into a trap with a superimposed magnetic bottle, in which the antiprotons oscillate along the magnetic field lines. Depending on their North-South alignment in the magnetic bottle, the antiprotons will vibrate at two slightly different rates. From these oscillations (combined with nuclear magnetic resonance methods), physicists can determine the magnetic moment.

    The challenge with this new measurement was developing a technique sensitive to the miniscule differences between antiprotons aligned with the magnetic field versus those anti-aligned.

    “It’s the equivalent of determining if a particle has vibrated 5 million times or 5 million-plus-one times over the course of a second,” Ulmer says. “Because this measurement is so sensitive, we stored antiprotons in the reservoir and performed the measurement when the antiproton decelerator was off and the lab was quiet.”

    BASE now plans to measure the antiproton magnetic moment using a new trapping technique that should enable a precision at the level of a few parts per billion—that is, a factor of 200 to 800 improvement.

    Members of the BASE experiment hope that a higher level of precision might provide clues as to why matter flourishes while cosmic antimatter lingers on the brink of extinction.

    “Every new precision measurement helps us complete the framework and further refine our understanding of antimatter’s relationship with matter,” Ulmer says.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 2:27 pm on January 7, 2017 Permalink | Reply
    Tags: Antimatter, CERN ALPHA Collaboration,   

    From UBC: “Behind ALPHA – UBC PHAS ALPHA members’ contributions” 

    U British Columbia bloc

    University of British Columbia

    2017-01-06
    No writer credit

    Since ALPHA – the Antihydrogen Laser Physics Apparatus Collaboration – first trapped and stored antihydrogen atoms in 2010, the international team has been making strides in advancing our understanding of antimatter.

    1

    AlphaCollaborationCERN ALPHA New
    CERN/ALPHA

    Just last month, results from their spectroscopic measurements were published in Nature. This brings us closer to learning why – if matter and antimatter were created equally during the Big Bang, where is all the antimatter? Among the 52 co-authors from 15 institutions in Canada, Brazil, Denmark, Israel, Japan, Sweden, UK, and the USA, we want to take an opportunity to recognize UBC PHAS ALPHA members’ contributions to the 1S-2S laser spectroscopy in ALPHA-2.

    Andrea Gutierrez was ALPHA-Canada collaboration spokesperson and TRIUMF Research Scientist Dr. Makoto Fujiwara’s graduate student, and recently graduated from PHAS with a PhD. She assisted in the construction of the ALPHA-2 apparatus, and in particular, she led the commissioning of the ALPHA-2 Catching Trap. She also developed a novel compression scheme for antiproton clouds, and participated in the analysis of particle detector data.

    Matt Grant, former PHAS Engineering Physics Program student, just started as graduate student at Stanford this fall. He did one co-op term with the ALPHA team, and then won a CERN summer student fellowship spending the summer 2015 at CERN, working on a laser imaging system.

    PHAS Professor Emeritus Walter Hardy and his graduate student Nathan Evetts, along with Professor Michael Hayden of SFU, have had responsibility for all microwave aspects of the experiment. In particular (along with PhD student Tim Friesen of Calgary), they conceived and implemented in-situ magnetometry via microwave heating of plasma modes of electrons in the ALPHA-2 electrode stack. This procedure was used extensively in the experiments.

    Walter and Nathan also conceived and fabricated novel cryogenic microwave filter tubes for the laser beam paths in the experiment. Eight of these tubes were installed for the 1S-2S laser spectroscopy experiment.

    Professor Takamasa Momose (Chemistry and PHAS) and his former PhD student, Mario Michan have had responsibility for the development of a Lyman-Alpha laser system for laser cooling of antihydrogen, which is necessary to improve the precision of the 1S-2S laser spectroscopy. Mario completed his PhD in January2014, and then worked at TRIUMF as a post-doc until April 2016.

    It is also worth mentioning that Makoto and Michael are both UBC PHAS alumni!

    Congratulations again, ALPHA team, on this tremendous breakthrough. We look forward to more discoveries in the year to come!

    See the full article here .

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    U British Columbia Campus

    The University of British Columbia is a global centre for research and teaching, consistently ranked among the 40 best universities in the world. Since 1915, UBC’s West Coast spirit has embraced innovation and challenged the status quo. Its entrepreneurial perspective encourages students, staff and faculty to challenge convention, lead discovery and explore new ways of learning. At UBC, bold thinking is given a place to develop into ideas that can change the world.

     
  • richardmitnick 10:39 am on December 22, 2016 Permalink | Reply
    Tags: Antimatter, , , , , Why Measuring Antimatter Is The Key To Our Universe   

    From Ethan Siegel: “Why Measuring Antimatter Is The Key To Our Universe” 

    From Ethan Siegel
    Dec 22, 2016

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    The galaxy cluster MACSJ0717.5+3745, must be made of matter just like we are, or there would be evidence of matter-antimatter annihilation along the line of sight. Image credit: NASA, ESA and the HST Frontier Fields team (STScI).

    When aliens come to our Solar System, hail us and send us their very first message, it likely won’t be, “take us to your leader,” but rather, “are you made of matter or antimatter?” Based on all the observations we’ve ever made, it appears that all the structures we know of in the Universe — planets, stars, gas, galaxies and more — are made of matter and not antimatter. There are signs of matter/antimatter annihilation, but the antimatter we see is less than 0.1% of the matter in all locations. On the one hand, we know our Universe is dominated by matter and not antimatter; we might be so confident in this fact that we’d be willing to shake hands with an alien without even asking the key question.

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    An artist’s conception of the planetary system Kepler-42. We have every reason to believe it’s all made of matter, and not antimatter. Image credit: NASA/JPL-Caltech.

    But on the other hand, every interaction that creates or destroys matter also creates or destroys an equal amount of antimatter. So how do we reconcile these two things? How do we have a Universe that exhibits perfectly symmetric interactions between matter and antimatter, yet that is made entirely of matter and not antimatter?

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    The particles and antiparticles of the Standard Model. Image credit: E. Siegel.

    There must be something that’s fundamentally different between the two. Figuring out exactly what those differences are will be key to understanding how our Universe — complete with galaxies, stars, planets, and human beings — came to exist. We’ve been able to measure the properties of matter incredibly well for many generations. We can measure:

    its mass,
    its acceleration in a gravitational field,
    its electric charge,
    its spin,
    its magnetic properties,
    how it binds together into atoms, molecules and larger structures,
    and how the electron transitions work in those varied configurations.

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    Electron transitions in the hydrogen atom, along with the wavelengths of the resultant photons. Image credit: Wikimedia Commons users Szdori and OrangeDog.

    Although there are other properties we can measure — decay rates, scattering amplitudes, cross sections, etc. — those are some of the most fundamental and important ones. They tell us the basics of how matter interacts with itself and with the gravitational and electromagnetic forces. If the laws of nature are completely symmetric, antimatter should have some particular properties that align identically as follows. The antimatter counterpart of every matter particle should have:

    the same mass,
    the same acceleration in a gravitational field,
    the opposite electric charge,
    the opposite spin,
    the same magnetic properties,
    should bind together the same way into atoms, molecules and larger structures,
    and should have the same spectrum of positron transitions in those varied configurations.

    Some of these have been measured for a long time: antimatter’s mass, electric charge, spin and magnetic properties are well-known. But those properties are easy to measure.

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    Trajectories of antihydrogen atoms from the ALPHA experiment. (Photo courtesy of Chukman So/University of California, Berkeley)

    At high enough energies, it’s easy to create additional matter/antimatter pairs by colliding particles into one another. As long as you have enough free energy to make a new particle and a new antiparticle — enough E to make the new masses as given by Einstein’s E = mc2 — you can simply create both matter and antimatter. As long as the antimatter doesn’t collide with another matter particle, which would cause it to instantaneously annihilate back into pure energy, you can determine its properties from the tracks it leaves behind in a detector. Its energy and momentum, as well as its electric charge and mass, can all be reconstructed by the trails it leaves behind when subjected to electric and magnetic fields.

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    Bubble chamber tracks from Fermilab, revealing the charge, mass, energy and momentum of the particles created. Image credit: FNAL / DOE / NSF.

    But because of its volatility, and how easy it is to destroy, antimatter is difficult to keep alive for a long time. You have to isolate it from any matter it would come into contact with. You need to slow, cool and confine it. And you need to coax it into binding with other, oppositely charged, equally precarious antimatter particles if you want to form anti-atoms. Remarkably, thanks to advances in technology and technique, the last decade has seen a remarkable set of advances on this front. We’ve been able to do that, and have created neutral anti-atoms.

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    In a simple hydrogen atom a single electron orbits a single proton. In an antihydrogen atom a single positron (anti-electron) orbits a single antiproton. Image credit: Lawrence Berkeley Labs.

    We’ve been able to isolate them and confine them, keeping them stable for over 10 minutes at a time. We’ve been able to measure their attractive and repulsive electric and nuclear forces, and are working on getting to the gravitational force. And earlier this month, for the first time, we measured the electron transitions in the anti-hydrogen atom, and determined they were equivalent in every way to the transitions in a hydrogen atom to better than one part in a billion (10^9).

    CERN ALPHA New
    CERN/ALPHA

    Yet the search continues. We’ve found a very subtle set of differences between the decays in the weak nuclear interaction between strange, charm and bottom quarks and their antiquark counterparts: the first hint that antimatter is different from matter. But it isn’t enough to explain why the Universe is made of matter and not antimatter. For that, we need additional physics. We need something that goes beyond the Standard Model, and beyond our standard expectations. So we continue to probe for new particles, for new interactions and for unexpected asymmetries. If we get lucky, we just might stumble upon the origin of why matter is everywhere, and antimatter isn’t.

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    One possible set of new particles, the Xs and Ys that arise in grand unification theories, could give rise to the matter-antimatter asymmetry. Image credit: E. Siegel, from his book, Beyond The Galaxy.

    But until then, our only option is to keep stabbing in the dark. To keep searching for the next decimal place; the next subtle effect to measure; the next, more advanced nuclear or atomic configuration to test. Nature may be slow to give up the secrets that are key to our existence, but we are persistent. Continuing to investigate the unlikely — or even the impossible — is the only way we know of to uncover the ultimate truth.

    See the full article here .

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

     
  • richardmitnick 11:50 am on December 19, 2016 Permalink | Reply
    Tags: Antimatter, , Ephemeral antimatter atoms pinned down in milestone laser test,   

    From Nature: “Ephemeral antimatter atoms pinned down in milestone laser test” 

    Nature Mag
    Nature

    19 December 2016
    Davide Castelvecchi

    CERN ALPHA New
    The ALPHA antimatter experiment at CERN has measured an energy transition in anti-hydrogen. CERN.

    In a technical tour-de-force, physicists have made of the first measurements of how antimatter atoms absorb light.

    Researchers at CERN, the European particle physics laboratory outside Geneva, trained an ultraviolet laser on antihydrogen, the antimatter counterpart of hydrogen. They measured the frequency of light needed to jolt a positron — an antielectron — from its lowest energy level to the next level up, and found no discrepancy with the corresponding energy transition in ordinary hydrogen.

    The null result is still a thrill for researchers who have been working for decades towards antimatter spectroscopy, the study of how light is absorbed and emitted by antimatter. The hope is that this field could provide a new test of a fundamental symmetry of the known laws of physics, called CPT (charge-parity-time) symmetry.

    CPT symmetry predicts that energy levels in antimatter and matter should be the same. Even the tiniest violation of this rule would require a serious rethink of the standard model of particle physics.

    Randolf Pohl, a spectroscopist at Johannes Gutenberg University in Mainz, Germany, could barely contain his excitement. “WOW,” he told Nature in an email. “After all these years, these guys have finally managed to do optical spectroscopy in antihydrogen. This is a milestone in the investigation of exotic atoms.”

    “It is amazing that one can control antimatter to an extent that this is possible,” says Michael Peskin, a theoretical physicist at the SLAC National Accelerator Laboratory in Menlo Park, California.

    Cold anti-hydrogen

    Studying antimatter is extremely difficult, because it annihilates whenever it comes into contact with ordinary matter. In 2010, CERN’s ALPHA collaboration demonstrated how to hold antihydrogen in a magnetic trap — and since then, have been working towards studying its interactions with light.

    Every 15 minutes or so, the ALPHA group can produce around 25,000 antihydrogen atoms. To make them, the physicists combine positrons, emitted by a radioactive substance, with antiprotons, produced by a particle accelerator and then slowed down and cooled.

    Most of these atoms are too ‘hot’ — moving too fast, and in too high an energy state — for spectroscopy studies. So the researchers must let them escape the magnetic trap, leaving just a handful of the slowest, lowest-energy antihydrogen atoms. Perfecting this technique took years, says ALPHA spokesperson Jeffrey Hangst. “Making antihydrogen is relatively easy; making cold antihydrogen is really difficult,” he says.

    Finally, the ALPHA team was able to see whether, when the researchers shone a laser at a particular frequency, the antihydrogen atoms would act like their hydrogen counterparts. The group says they do: the energy transition is consistent to a precision of 2 parts in 10 billion, they report on 19 December in Nature.

    “You put so much effort into something, and it finally succeeds. There are almost no words to describe it,” says Hangst.

    Next, the researchers hope to probe the antihydrogen with a large range of laser energies. That could provide a more stringent test of matter–antimatter equivalence and of CPT symmetry.

    Many theories — such as string theory — that venture beyond the standard model by combining gravity with the three other fundamental forces of subatomic physics, do involve some kind of CPT violation, says Peskin. “So it is not at all clear that CPT is a true symmetry of nature,” he says.

    Two other experiments at CERN — called ATRAP and ASACUSA — were competing with ALPHA to measure antimatter spectroscopy. Gerald Gabrielse, the leader of ATRAP and a physicist at Harvard University in Cambridge, Massachusetts, says he first proposed nearly 30 years ago measuring the particular energy transition in antihydrogen that the ALPHA team have reported. “We started ten years earlier and they got to this result first,” he says. ”Congratulations to ALPHA.”

    See the full article here .

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    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

     
  • richardmitnick 2:20 pm on November 29, 2016 Permalink | Reply
    Tags: Antimatter, , ,   

    From CERN: “A new ring to slow down antimatter” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    28 Nov 2016
    Corinne Pralavorio
    Posted by Harriet Kim Jarlett

    1
    The new deceleration ring ELENA will slow down antimatter particles further than ever to improve the efficiency of experiments studying antimatter. (Image: Maximilien Brice/CERN)

    You could mistake ELENA for a miniature accelerator. But, unlike most accelerators, it’s housed in a hangar and you can take it all in in just a single glance. The biggest difference though, is that it doesn’t accelerate particles, but decelerates them.

    CERN’s brand-new machine measures just 30 metres in circumference and has just begun its first tests with beam.

    The ELENA (Extra Low ENergy Antiproton) deceleration ring will be connected to the Antiproton Decelerator (AD), which has been in service since 2000. The AD is a unique facility that enables the study of antimatter.

    Antimatter can be thought of as a mirror image of matter and it remains a mystery for physicists. For example, matter and antimatter should have been created in equal quantities at the time of the Big Bang— the event at the origin of our Universe. But antimatter seems to have disappeared from the Universe. Where it has gone is one of the many questions physicists are trying to solve with the AD machine.

    The 182-metre-circumference ring decelerates antiprotons (the anti-particles of protons) to 5.3 MeV, the lowest energy possible in a machine of this size. The antiprotons are then sent to experiments where they are studied or used to produce atoms of antimatter. The slower the antiprotons (i.e. the less energy they have), the easier it is for the experiments to study or manipulate them.

    And this is where ELENA comes in. Coupled with the AD, this small ring will slow the antiprotons down even further, reducing their energy by a factor of 50, from 5.3 MeV to just 0.1 MeV. In addition, the density of the beams will be improved. The experiments will be able to trap 10 to 100 times more antiprotons, improving efficiency and paving the way for new studies.

    Decelerating beams is just as complicated as accelerating them. The slower the particles, the harder it is to control their trajectories. At low energy, beams are more sensitive to outside interference, such as the earth’s magnetic field. ELENA is therefore equipped with magnets that are optimised to operate with very weak fields. An electron cooling system concentrates and decelerates the beams.

    Now that the components of the new decelerator have been installed, the teams have begun the first tests with beam.

    “After five years of development and construction, this is a very important stage. We are going to continue the tests over the coming weeks to see if everything is working as planned,” explains Christian Carli, ELENA project leader. “GBAR, the first experiment to be connected to ELENA, should receive its first antiprotons in 2017.”

    The other experiments will be connected during the second long shutdown of CERN’s accelerators in 2019-2020. ELENA will supply antiprotons to four experiments in parallel.

    Several experiments are studying antimatter and its properties: ALPHA, ASACUSA, ATRAP and BASE. GBAR and AEGIS are working more specifically on the effect of gravity on antimatter.

    You can read more about ELENA in the the CERN Courier.

    See the full article here.

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    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 1:40 pm on May 3, 2016 Permalink | Reply
    Tags: Antimatter, , EXO-200 experiment, ,   

    From Symmetry: “EXO-200 resumes its underground quest” 

    Symmetry Mag
    Symmetry

    05/03/16
    Matthew R. Francis

    EXO-200 Enriched Xenon Observatory near Carlsbad, New Mexico
    SLAC EXO-200 Enriched Xenon Observatory near Carlsbad, New Mexico

    The upgraded experiment aims to discover if neutrinos are their own antiparticles.

    Science is often about serendipity: being open to new results, looking for the unexpected.

    The dark side of serendipity is sheer bad luck, which is what put the Enriched Xenon Observatory experiment, or EXO-200, on hiatus for almost two years.

    Accidents at the Department of Energy’s underground Waste Isolation Pilot Project (WIPP) facility near Carlsbad, New Mexico, kept researchers from continuing their search for signs of neutrinos and their antimatter pairs. Designed as storage for nuclear waste, the site had both a fire and a release of radiation in early 2014 in a distant part of the facility from where the experiment is housed. No one at the site was injured. Nonetheless, the accidents, and the subsequent efforts of repair and remediation, resulted in a nearly two-year suspension of the EXO-200 effort.

    Things are looking up now, though: Repairs to the affected area of the site are complete, new safety measures are in place, and scientists are back at work in their separate area of the site, where the experiment is once again collecting data. That’s good news, since EXO-200 is one of a handful of projects looking to answer a fundamental question in particle physics: Are neutrinos and antineutrinos the same thing?

    The neutrino that wasn’t there

    Each type of particle has its own nemesis: its antimatter partner. Electrons have positrons—which have the same mass but opposite electric charge—quarks have antiquarks and protons have antiprotons. When a particle meets its antimatter version, the result is often mutual annihilation. Neutrinos may also have antimatter counterparts, known as antineutrinos. However, unlike electrons and quarks, neutrinos are electrically neutral, so antineutrinos look a lot like neutrinos in many circumstances.

    In fact, one hypothesis is that they are one and the same. To test this, EXO-200 uses 110 kilograms of liquid xenon (of its 200kg total) as both a particle source and particle detector. The experiment hinges on a process called double beta decay, in which an isotope of xenon has two simultaneous decays, spitting out two electrons and two antineutrinos. (“Beta particle” is a nuclear physics term for electrons and positrons.)

    If neutrinos and antineutrinos are the same thing, sometimes the result will be neutrinoless double beta decay. In that case, the antineutrino from one decay is absorbed by the second decay, canceling out what would normally be another antineutrino emission. The challenge is to determine if neutrinos are there or not, without being able to detect them directly.

    “Neutrinoless double beta decay is kind of a nuclear physics trick to answer a particle physics problem,” says Michelle Dolinski, one of the spokespeople for EXO-200 and a physicist at Drexel University. It’s not an easy experiment to do.

    EXO-200 and similar experiments look for indirect signs of neutrinoless double beta decay. Most of the xenon atoms in EXO-200 are a special isotope containing 82 neutrons, four more than the most common version found in nature. The isotope decays by emitting two electrons, changing the atom from xenon into barium. Detectors in the EXO-200 experiment collect the electrons and measure the light produced when the beta particles are stopped in the xenon. These measurements together are what determine whether double beta decay happened, and whether the decay was likely to be neutrinoless.

    EXO-200 isn’t the only neutrinoless double beta decay experiment, but many of the others use solid detectors instead of liquid xenon. Dolinski got her start on the CUORE experiment, a large solid-state detector, but later changed directions in her research.

    CUORE experiment UC Berkeley
    CUORE experiment UC Berkeley

    “I joined EXO-200 as a postdoc in 2008 because I thought that the large liquid detectors were a more scalable solution,” she says. “If you want a more sensitive liquid-state experiment, you can build a bigger tank and fill it with more xenon.”

    Neutrinoless or not, double beta decay is very rare. A given xenon atom decays randomly, with an average lifetime of a quadrillion times the age of the universe. However, if you use a sufficient number of atoms, a few of them will decay while your experiment is running.

    “We need to sample enough nuclei so that you would detect these putative decays before the researcher retires,” says Martin Breidenbach, one of the EXO-200 project leaders and a physicist at the Department of Energy’s SLAC National Accelerator Laboratory.

    But the experiment is not just detecting neutrinoless events. Heavier neutrinos mean more frequent decays, so measuring the rate reveals the neutrino mass — something very hard to measure otherwise.

    Prior runs of EXO-200 and other experiments failed to see neutrinoless double beta decay, so either neutrinos and antineutrinos aren’t the same particle after all, or the neutrino mass is small enough to make decays too rare to be seen during the experiment’s lifetime. The current limit for the neutrino mass is less than 0.38 electronvolts—for comparison, electrons are about 500,000 electronvolts in mass.

    2
    SLAC National Accelerator Laboratory’s Jon Davis checks the enriched xenon storage bottles before the refilling of the TPC. Brian Dozier, Los Alamos National Laboratory

    Working in the salt mines

    Cindy Lin is a Drexel University graduate student who spends part of her time working on the EXO-200 detector at the mine. Getting to work is fairly involved.

    “In the morning we take the cage elevator half a mile down to the mine,” she says. Additionally, she and the other workers at WIPP have to take a 40-hour safety training to ensure their wellbeing, and wear protective gear in addition to normal lab clothes.

    “As part of the effort to minimize salt dust particles in our cleanroom, EXO-200 scientists also cover our hair and wear coveralls,” Lin adds.

    The sheer amount of earth over the detector shields it from electrons and other charged particles from space, which would make it too hard to spot the signal from double beta decay. WIPP is carved out of a sodium chloride deposit—the same stuff as table salt—that has very little uranium or the other radioactive minerals you find in solid rock caverns. But it has its drawbacks, too.

    “Salt is very dynamic: It moves at the level of centimeters a year, so you can’t build a nice concrete structure,” says Breidenbach. To compensate, the EXO-200 team has opted for a more modular design.

    The inadvertent shutdown provided extra challenges. EXO-200, like most experiments, isn’t well suited for being neglected for more than a few days at a time. However, Lin and other researchers worked hard to get the equipment running for new data this year, and the downtime also allowed researchers to install some upgraded equipment.

    The next phase of the experiment, nEXO, is at a conceptual stage based on what has been learned from EXO200. Experimenters are considering the benefits of moving the project deeper underground, perhaps at a facility like the Sudbury Neutrino Observatory (SNOlab) in Canada.
    SNOLAB, Sudbury, Ontario, Canada.
    SNOLAB
    SNOLAB, Sudbury, Ontario, Canada

    Dolinski is optimistic that if there are any neutrinoless double beta decays to see, nEXO or similar experiments should see them in the next 15 years or so.

    Then, maybe we’ll know if neutrinos and antineutrinos are the same and find out more about these weird low-mass particles.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 12:30 pm on March 2, 2016 Permalink | Reply
    Tags: Antimatter, , , , , , SuperKEKB reborn   

    From Symmetry: “SuperKEKB reborn” 

    Symmetry

    03/02/16
    Lauren Biron

    SuperKEKB accelerator
    KEK SuperKEKB accelerator. No image credit found.

    The Japanese accelerator takes its first steps toward resuming its hunt for the universe’s missing antimatter.

    Everyone knows the electron, but in our daily routines of charging laptops and phones, we don’t often think of its antiparticle, the positron. Where has all the antimatter gone, in the long time passing since the dawn of the universe?

    That’s what scientists working on Japan’s electron-positron colliding accelerator, SuperKEKB, hope to find out. They’ll accelerate electrons and their antimatter brothers close to the speed of light before slamming them together. By peering into the debris and searching for rare particle decays, they’ll try to figure out why we live in a world full of matter.

    Japan’s high-energy accelerator research organization, known as KEK, announced today that scientists successfully accelerated and stored electrons and positrons in their separate rings, each nearly 2 miles around. This is the first in several steps to commission the accelerator after a five-year upgrade that included new beam pipes, new magnets (and magnet power supplies) to guide the beam, and a reinforced radio-frequency system that accelerates the particles. Technicians also added a new positron source for the antimatter particles and a new electron gun.

    The improvements should create many more collisions per second than the previous iteration of the accelerator, KEKB, was capable of–and that means a better chance of seeing interesting particle decays. The collisions will create pairs of bottom quarks and bottom antiquarks, hence the “B” in SuperKEKB.

    The project will also involve an upgraded version of the Belle detector that previously recorded the collisions.

    KEK Belle detector
    Belle

    The initial run of the Belle detector yielded some interesting results, including a difference in the way particles called B mesons decayed. The asymmetry, called CP violation, was an intriguing find.

    “This is still puzzling,” KEK Director-General Masanori Yamauchi said in a Symmetry interview last year. “We still don’t know how it happens. We need at least 10 times more data to find out. That’s why we started the upgrade of KEKB.”

    The rare decays that Belle II will try to capture might also have occurred early in our universe’s history. Replicating them could provide clues to the current matter-antimatter imbalance and help us better understand the physics that underlies our cosmos, which can’t be fully explained by the current Standard Model.

    Standard model with Higgs New
    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.

    Before that can happen, researchers need to tune the accelerator so it operates perfectly, a process slated to take through June. They’ll also add powerful superconducting magnets that will focus the beam and install the Belle II detector. Once it is in place and working properly, they’ll get back to work on the case of the missing antimatter.

    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 3:58 pm on January 20, 2016 Permalink | Reply
    Tags: Antimatter, , , ,   

    From Symmetry: “Is the neutrino its own antiparticle?” 

    Symmetry

    01/20/16
    Signe Brewster

    The mysterious particle could hold the key to why matter won out over antimatter in the early universe.

    Temp 1
    Artwork by Sandbox Studio, Chicago with Ana Kova

    Almost every particle has an antimatter counterpart: a particle with the same mass but opposite charge, among other qualities.

    This seems to be true of neutrinos, tiny particles that are constantly streaming through us. Judging by the particles released when a neutrino interacts with other matter, scientists can tell when they’ve caught a neutrino versus an antineutrino.

    But certain characteristics of neutrinos and antineutrinos make scientists wonder: Are they one and the same? Are neutrinos their own antiparticles?

    This isn’t unheard of. Gluons and even Higgs bosons are thought to be their own antiparticles. But if scientists discover neutrinos are their own antiparticles, it could be a clue as to where they get their tiny masses—and whether they played a part in the existence of our matter-dominated universe.

    Dirac versus Majorana

    The idea of the antiparticle came about in 1928 when British physicist Paul Dirac developed what became known as the Dirac equation. His work sought to explain what happened when electrons moved at close to the speed of light. But his calculations resulted in a strange requirement: that electrons sometimes have negative energy.

    “When Dirac wrote down his equation, that’s when he learned antiparticles exist,” says André de Gouvêa, a theoretical physicist and professor at Northwestern University. “Antiparticles are a consequence of his equation.”

    Physicist Carl Anderson discovered the antimatter partner of the electron that Dirac foresaw in 1932. He called it the positron—a particle like an electron but with a positive charge.

    Dirac predicted that, in addition to having opposite charges, antimatter partners should have opposite handedness as well.

    A particle is considered right-handed if its spin is in the same direction as its motion. It is considered left-handed if its spin is in the opposite direction.

    Dirac’s equation allowed for neutrinos and anti-neutrinos to be different particles, and, as a result, four types of neutrino were possible: left- and right-handed neutrinos and left- and right-handed antineutrinos. But if the neutrinos had no mass, as scientists thought at the time, only left-handed neutrinos and right-handed antineutrinos needed to exist.

    In 1937, Italian physicist Ettore Majorana debuted another theory: Neutrinos and antineutrinos are actually the same thing. The Majorana equation described neutrinos that, if they happened to have mass after all, could turn into antineutrinos and then back into neutrinos again.

    Temp 2
    Artwork by Sandbox Studio, Chicago with Ana Kova

    The matter-antimatter imbalance

    Whether neutrino masses were zero remained a mystery until 1998, when the Super-Kamiokande and SNO experiments found they do indeed have very small masses—an achievement recognized with the 2015 Nobel Prize for Physics.

    Super-Kamiokande Detector
    Super-Kamiokande neutrino detector

    SNOLAB
    SNO detector [under construction]

    Since then, experiments have cropped up across Asia, Europe and North America searching for hints that the neutrino is its own antiparticle.

    The key to finding this evidence is something called lepton number conservation. Scientists consider it a fundamental law of nature that lepton number is conserved, meaning that the number of leptons and anti-leptons involved in an interaction should remain the same before and after the interaction occurs.

    Scientists think that, just after the big bang, the universe should have contained equal amounts of matter and antimatter. The two types of particles should have interacted, gradually canceling one another until nothing but energy was left behind. Somehow, that’s not what happened.

    Finding out that lepton number is not conserved would open up a loophole that would allow for the current imbalance between matter and antimatter. And neutrino interactions could be the place to find that loophole.

    Neutrinoless double-beta decay

    Scientists are looking for lepton number violation in a process called double beta decay, says SLAC theorist Alexander Friedland, who specializes in the study of neutrinos.

    In its common form, double beta decay is a process in which a nucleus decays into a different nucleus and emits two electrons and two antineutrinos. This balances leptonic matter and antimatter both before and after the decay process, so it conserves lepton number.

    If neutrinos are their own antiparticles, it’s possible that the antineutrinos emitted during double beta decay could annihilate one another and disappear, violating lepton number conservation. This is called neutrinoless double beta decay.

    Such a process would favor matter over antimatter, creating an imbalance.

    “Theoretically it would cause a profound revolution in our understanding of where particles get their mass,” Friedland says. “It would also tell us there has to be some new physics at very, very high energy scales—that there is something new in addition to the Standard Model we know and love.”

    Standard Model
    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’s possible that neutrinos and antineutrinos are different, and that there are two neutrino and anti-neutrino states, as called for in Dirac’s equation. The two missing states could be so elusive that physicists have yet to spot them.

    But spotting evidence of neutrinoless double beta decay would be a sign that Majorana had the right idea instead—neutrinos and antineutrinos are the same.

    “These are very difficult experiments,” de Gouvêa says. “They’re similar to dark matter experiments in the sense they have to be done in very quiet environments with very clean detectors and no radioactivity from anything except the nucleus you’re trying to study.”

    Physicists are still evaluating their understanding of the elusive particles.

    “There have been so many surprises coming out of neutrino physics,” says Reina Maruyama, a professor at Yale University associated with the CUORE neutrinoless double beta decay experiment.

    CUORE experiment
    CUORE neutrinoless double beta decay experiment at Gran Sasso in Italy.

    “I think it’s really exciting to think about what we don’t know.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
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