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  • richardmitnick 2:33 pm on August 2, 2017 Permalink | Reply
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    From CERN: “The ALPHA experiment explores the secrets of antimatter” 

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    02 Aug 2017
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    Alpha Experiment (Image: CERN)

    3 August 2017. In a paper published today in Nature, the ALPHA experiment at CERN’s Antiproton Decelerator reports the first observation of the hyperfine structure of antihydrogen, the antimatter counterpart of hydrogen. These findings point the way to ever more detailed analyses of the structure of antihydrogen and could help understand any differences between matter and antimatter.

    The researchers conducted spectroscopy measurements on homemade antihydrogen atoms, which drive transitions between different energy states of the anti-atoms. They could in this way improve previous measurements by identifying and measuring two spectral lines of antihydrogen. Spectroscopy is a way to probe the internal structure of atoms by studying their interaction with electromagnetic radiation.

    In 2012, the ALPHA experiment demonstrated for the first time the technical ability to measure the internal structure of atoms of antimatter. In 2016 [Nature], the team reported the first observation of an optical transition of antihydrogen. By exposing antihydrogen atoms to microwaves at a precise frequency, they have now induced hyperfine transitions and refined their measurements. The team were able to measure two spectral lines for antihydrogen, and observe no difference compared to the equivalent spectral lines for hydrogen, within experimental limits.

    “Spectroscopy is a very important tool in all areas of physics. We are now entering a new era as we extend spectroscopy to antimatter,” said Jeffrey Hangst, Spokesperson for the ALPHA experiment. “With our unique techniques, we are now able to observe the detailed structure of antimatter atoms in hours rather than weeks, something we could not even imagine a few years ago.”

    With their trapping techniques, ALPHA are now able to trap a significant number of antiatoms – up to 74 at a time – thereby facilitating precision measurements. With this new result, the ALPHA collaboration has clearly demonstrated the maturity of its techniques for probing the properties of antimatter atoms.

    The rapid progress of CERN’s experiments at the unique Antiproton Decelerator facility is very promising for ever more precise measurements to be carried out in the near future.

    See the full article here.

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  • richardmitnick 10:39 am on December 22, 2016 Permalink | Reply
    Tags: , , CERN ALPHA, , , 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

    1
    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).

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    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: , CERN ALPHA, Ephemeral antimatter atoms pinned down in milestone laser test,   

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

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    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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  • richardmitnick 11:23 am on June 17, 2014 Permalink | Reply
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    From Berkeley Lab: “Precision Physics of Antiatoms: Berkeley Lab Physicists Bound the Charge of Antihydrogen” 

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    June 13, 2014
    Kate Greene

    Hydrogen is a neutral atom. Its single electron orbits a single proton, and the net effect is no electrical charge. But what about hydrogen’s antimatter counterpart, antihydrogen? Made of a positron that orbits an antiproton, the antihydrogen atom should be neutral too. Various results have indicated as much, but because the charge of antiatoms is difficult to measure, it has remained an open question.

    A recent experiment to measure the charge of antihydrogen has now placed a bound on the atom’s charge. Physicists from Berkeley Lab, the University of California, and other institutions part of the ALPHA collaboration at CERN, have published in Nature Communications a new measurement of the charge of antihydrogen, determined with unprecedented precision.

    The result: effectively zero. Specifically, antihydrogen’s charge is less than 20 billionths of the magnitude of the electron charge, a measurement that’s a million-fold improvement over the best previous experiment. This is good news for fundamental theories of physics.

    “We would expect the charge of hydrogen and antihydrogen to be the same,” says Jonathan Wurtele, physicist at Berkeley Lab and UC and author on the paper. “If we had seen a charge, we would have new physics. ”

    Antihydrogen resists easy measurement for a number of reasons, starting with its production. While positrons are relatively straightforward to obtain, low energy antiprotons are only available at the Antiproton Decelerator at CERN. (Antiprotons were first created in 1955 at Berkeley Lab’s now decommissioned Bevatron accelerator.)

    Once produced through high-energy collisions, the particles then need to be slowed down and cooled. Next, electrodes manipulate the electric field to mix antiprotons with positrons, making a few atoms of antihydrogen. These atoms are then trapped in a magnetic “bottle.” It takes thousands of positron-antiproton mixings to produce just 500 atoms of trapped antihydrogen.

    The experimental measurements only happens when the magnetic field trap is turned off, effectively pouring atoms out of the bottle and into a vacuum chamber. Once free, an atom of antihydrogen will contact an atom of normal matter on the trap wall, and the two annihilate each other. This annihilation leaves a signal, evidence of the antihydrogen’s position.

    For the charge-measurement experiment, the scientists took advantage of the fact that there were strong electric fields within the trap. “If the antiatom were charged”, says Joel Fajans, physicist at UC and Berkeley Lab “these fields would push the antiatom to the left side or to the right side of the trap, depending on the putative sign of antihydrogen charge.” Analysis of data showed that there was no tendency for the anti-atoms to go to the left or right, implying that the atom was electrically neutral.

    atom
    When an anti-atom is put into an electric field, does it feel a force? It will only feel a force if it has a net charge. Normal matter atoms are known to be charge neutral to an extraordinary precision, and modern physics theories assert that anti-atoms would be similarly charge neutral. New Berkeley Lab research confirms that antihydrogen atoms are indeed charge neutral to at least nearly 10ppb of the unit charge. Credit: Joel Fajans, Berkeley

    Fajans, Wurtele, and Marcello Baquero-Ruiz and Alex Povilus, both graduate students in the physics department at the University of California, as well as Berkeley post-doc Andre Zhmoginov, Berkeley instructor Andrew Charman, and Berkeley undergraduate Arielle Little, did much of the simulation work and modeling of the system as well as developing statistical techniques for data analysis. The data itself was collected by the entire ALPHA collaboration.

    Other recent work by the Berkeley group and Francis Robicheaux at Purdue indicates that future experimental bounds could reach approximately 100 times higher precision using a technique based on an approach called stochastic acceleration.

    Previously, Fajans and Wurtele were involved in ALPHA experiments to measure the microwave spectrum of antihydrogen as well as the effects of gravity on antihydrogen, which, as far as experiments can currently determine, interacts with it the same as it does hydrogen. Next up are measurements of the anti-atoms’ energy levels.

    A better understanding of the properties of antimatter in general and anti atoms in particular is important to solving the so-called baryogenesis problem, which essentially questions why the universe has more matter than antimatter.

    “People have been trying to explain the baryogenesis problem for years without success. It seems that our current understanding is incomplete,” says Fajans. “There are some possible straightforward explanations out there, but physicists wonder if the baryogenesis problem can only be explained by something more interesting or exotic. Anomalies with antihydrogen could be the answer.”

    This research was funded in part by the U.S. Department of Energy and the Laboratory Directed Research and Development program at Berkeley Lab.

    See the full article here.

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  • richardmitnick 5:24 pm on June 3, 2014 Permalink | Reply
    Tags: , Antihydrogen, , CERN ALPHA,   

    From CERN: “CERN’s ALPHA experiment measures charge of antihydrogen” 

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    3 Jun 2014
    Cian O’Luanaigh

    In a paper published in the journal Nature Communications today, the ALPHA experiment at CERN’s Antiproton Decelerator (AD) reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places. Although this result comes as no surprise, since hydrogen atoms are electrically neutral, it is the first time that the charge of an antiatom has been measured to high precision.

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    “This is the first time we have been able to study antihydrogen with some precision,” said ALPHA spokesperson Jeffrey Hangst. “We are optimistic that ALPHA’s trapping technique will yield many such insights in the future. We look forward to the restart of the AD program in August, so that we can continue to study antihydrogen with ever increasing accuracy.”

    Antiparticles should be identical to matter particles except for the sign of their electric charge. So while the hydrogen atom is made up of a proton with charge +1 and an electron with charge -1, the antihydrogen atom consists of a charge -1 antiproton and a charge +1 positron. We know, however, that matter and antimatter are not exact opposites – nature seems to have a one-part in 10 billion preference for matter over antimatter, so it is important to measure the properties of antimatter to great precision: the principal goal of CERN’s AD experiments. ALPHA achieves this by using a complex system of particle traps that allow antihydrogen atoms to be produced and stored for long enough periods to study in detail. Understanding matter antimatter asymmetry is one of the greatest challenges in physics today. Any detectable difference between matter and antimatter could help solve the mystery and open a window to new physics.

    cryo
    Detail of the ALPHA experiment: Insertion of the ALPHA Penning trap into the cryostat that holds the antihydrogen trapping magnets (Image: Niels Madsen)

    To measure the charge of antihydrogen, the ALPHA experiment studied the trajectories of antihydrogen atoms released from the trap in the presence of an electric field. If the antihydrogen atoms had an electric charge, the field would deflect them, whereas neutral atoms would be undeflected. The result, based on 386 recorded events, gives a value of the antihydrogen electric charge as (-1.3±1.1±0.4) × 10-8, the plus or minus numbers representing statistical and systematic uncertainties on the measurement.

    With the restart of CERN’s accelerator chain getting underway, the laboratory’s antimatter research programme is set to resume. Experiments including ALPHA-2, an upgraded version of the ALPHA experiment, will be taking data along with the ATRAP and ASACUSA experiments and newcomer AEGIS, which will be studying the influence of gravity on antihydrogen.

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    Read more: An experimental limit on the charge of antihydrogen

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  • richardmitnick 2:25 pm on April 14, 2014 Permalink | Reply
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    From PhysicsWorld.com: “Interferometry tips the scales on antimatter” 

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    Apr 7, 2014

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    A new technique for measuring how antimatter falls under gravity has been proposed by researchers in the US. The team says that its device – based on cooling atoms of antimatter and making them interfere – could also help to test Einstein’s equivalence principle with antihydrogen – something that could have far-reaching consequences for cosmology. Finding even the smallest of differences between the behaviour of matter and antimatter could shine a light on why there is more matter than antimatter in the universe today, as well as help us to better understand the nature of the dark universe.

    alpha
    Trapping potential: The ALPHA experiment at CERN

    Up or down?

    First detected at CERN in 1995, physicists have long wondered how antimatter is affected by gravity – does it fall up or down? Most theoretical and experimental work suggests that gravity probably acts in exactly the same way on antimatter as it does on matter. The problem is that antimatter is difficult to produce and study, meaning that no direct experimental measurements of its behaviour under gravity have been made to date.

    One big step forward took place last year, when researchers at the ALPHA experiment at CERN measured how long it takes atoms of antihydrogen – made up of a positron surrounding an antiproton – to reach the edges of a magnetic trap after it is switched off. Although ALPHA did not find any evidence of the antihydrogen responding differently to gravity, the team was able to rule out the possibility that antimatter responds much more strongly to gravity than matter.

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    Alpha Collaboration’s Official image

    Waving matter

    Such experiments are hard to carry out, however – antimatter is difficult to produce on a large scale and it annihilates when it comes into contact with regular matter, making it difficult to trap and hold. The new interferometry technique – proposed by Holger Müller and colleagues at the University of California, Berkeley, and Auburn University in Alabama – exploits the fact that a beam of antimatter atoms can, like light, be split, sent along two paths and made to interfere, with the amount of interference depending on the phase shift between the two beams. The researchers say the light-pulse atom interferometer, which they plan to install at the ALPHA experiment, could work not only with almost any type of atom or anti-atom, but also with electrons and protons.

    In the proposed interferometer, the matter waves would be split and recombined using pulses of laser light. If an atom interacts with the laser beam, it will receive a “kick” from the momentum of a pair of photons, creating the split, explains Müller. By tuning the laser to the correct pulse energy, this process can be made to happen with a probability of 50%, sending the matter waves along either of the two arms of the interferometer. When the paths join again, the probability of detecting the anti-atom depends on the amplitude of the matter wave, which becomes a function of the phase shift.

    Annihilation danger?

    Müller adds that the phase shift depends on the acceleration due to gravity (g), the momentum of the photons (and so the magnitude of the kick) and the time interval between each laser pulse. Measuring the phase shift is therefore a way of measuring g, because the momentum and the time interval are both known. The biggest advantage of the technique is that the anti-atoms will not be in danger of annihilating because they will never come close to any mechanical objects, being moved with light and magnetic fields only.

    Müller’s idea is to combine two proven technologies: light-pulse atom interferometry and ALPHA’s method of producing antihydrogen using its Penning trap. He points out that the team’s proposed method does not assume availability of a laser resonant with the Lyman-alpha transition in hydrogen, which can be very difficult to build. To make the whole experiment even more efficient, the team has also developed what Müller describes as an “atom recycling method”, which allows the researchers to work with “realistic” atom numbers. “The atom is enclosed inside magnetic fields that prevent it from going away. Thus, an atom that hasn’t been hit by the laser on our first attempt has a chance to get hit later. This way, we can use almost every single atom – a crucial feat at a production rate of one every 15 minutes,” he explains. This would let ALPHA measure the gravitational acceleration of antihydrogen to a precision of 1%.

    Precise and accurate

    The team plans to build a demo set-up at Berkeley, which will work with regular hydrogen, and hopes to secure funding for this soon. Müller and colleagues are now also part of the APLHA collaboration. “The work at CERN will proceed in several steps,” he says. “The first is an up/down measurement telling [us] whether the antimatter will go up or down,” he says. This will be followed by a measurement of per-cent-level accuracy. Müller’s long-term aim is get to a precision of 10–6, which would be vastly superior to ALPHA’s measurement last year, which has an error bar of 102. ALPHA can currently trap and hold atoms at the rate of four each hour, but thanks to recent upgrades at its source of antiprotons – the ELENA ring – CERN could theoretically produce nearly 3000 atoms per month. In addition to ALPHA, the GBAR and AEgIS collaborations are also planning to measure gravity’s effects on antimatter.

    While Müller agrees that the gravitational behaviour of antimatter can be studied from experiments with normal matter, a direct observation is essential, and that is what Müller, the ALPHA collaboration and the other teams at CERN are keen to accomplish in the near future. “No matter how sound one’s theory, there is no substitute in science for a direct observation,” he says.

    See the full article here.

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    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.

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