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  • richardmitnick 11:44 am on February 19, 2020 Permalink | Reply
    Tags: , , , CERN ALPHA-g, ,   

    From CERN ALPHA: “ALPHA collaboration at CERN reports first measurements of certain quantum effects in antimatter” 

    Cern New Bloc

    Cern New Particle Event


    From CERN ALPHA-g

    2.19.20

    The ALPHA collaboration at CERN has reported the first measurements of certain quantum effects in the energy structure of antihydrogen, the antimatter counterpart of hydrogen. These quantum effects are known to exist in matter, and studying them could reveal as yet unobserved differences between the behaviour of matter and antimatter. The results, described in a paper published today in the journal Nature, show that these first measurements are consistent with theoretical predictions of the effects in “normal” hydrogen, and pave the way for more precise measurements of these and other fundamental quantities.

    “Finding any difference between these two forms of matter would shake the foundations of the Standard Model of particle physics, and these new measurements probe aspects of antimatter interaction – such as the Lamb shift – that we have long looked forward to addressing,” says Jeffrey Hangst, spokesperson for the ALPHA experiment.

    Standard Model of Particle Physics, Quantum Diaries

    “Next on our list is chilling large samples of antihydrogen using state-of-the-art laser cooling techniques. These techniques will transform antimatter studies and will allow unprecedentedly high-precision comparisons between matter and antimatter.”

    The ALPHA team creates antihydrogen atoms by binding antiprotons delivered by CERN’s Antiproton Decelerator with antielectrons, more commonly called “positrons”.

    3
    CERN Antimatter factory – antiproton decelerator main device. Wikepedia

    CERN ALPHA-g experiment being installed at CERN’s Antiproton Decelerator hall. (Image CERN)

    It then confines them in a magnetic trap in an ultra-high vacuum, which prevents them from coming into contact with matter and annihilating. Laser light is then shone onto the trapped atoms to measure their spectral response. This technique helps measure known quantum effects like the so-called fine structure and the Lamb shift, which correspond to tiny splittings in certain energy levels of the atom, and were measured in this study in the antihydrogen atom for the first time. The team previously used this approach to measure other quantum effects in antihydrogen, the latest being a measurement of the Lyman-alpha transition.

    The fine structure was measured in atomic hydrogen more than a century ago, and laid the foundation for the introduction of a fundamental constant of nature that describes the strength of the electromagnetic interaction between elementary charged particles. The Lamb shift was discovered in the same system about 70 years ago and was a key element in the development of quantum electrodynamics, the theory of how matter and light interact.

    The Lamb-shift measurement, which won Willis Lamb the Nobel Prize in Physics in 1955, was reported in 1947 at the famous Shelter Island conference – the first important opportunity for leaders of the American physics community to gather after the war.

    Technical Note:
    Both the fine structure and the Lamb shift are small splittings in certain energy levels (or spectral lines) of an atom, which can be studied with spectroscopy. The fine-structure splitting of the second energy level of hydrogen is a separation between the so-called 2P3/2 and 2P1/2 levels in the absence of a magnetic field. The splitting is caused by the interaction between the velocity of the atom’s electron and its intrinsic (quantum) rotation. The “classic” Lamb shift is the splitting between the 2S1/2 and 2P1/2 levels, also in the absence of a magnetic field. It is the result of the effect on the electron of quantum fluctuations associated with virtual photons popping in and out of existence in a vacuum.

    In their new study, the ALPHA team determined the fine-structure splitting and the Lamb shift by inducing and studying transitions between the lowest energy level of antihydrogen and the 2P3/2 and 2P1/2 levels in the presence of a magnetic field of 1 Tesla. Using the value of the frequency of a transition that they had previously measured, the 1S–2S transition, and assuming that certain quantum interactions were valid for antihydrogen, the researchers inferred from their results the values of the fine-structure splitting and the Lamb shift. They found that the inferred values are consistent with theoretical predictions of the splittings in “normal” hydrogen, within the experimental uncertainty of 2% for the fine-structure splitting and of 11% for the Lamb shift.

    Received via email.


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    CERN ALPHA Antimatter Factory


    CERN ALPHA Detector

     
  • richardmitnick 8:42 am on November 2, 2018 Permalink | Reply
    Tags: , , CERN ALPHA-g, , , ,   

    From CERN: “New antimatter gravity experiments begin at CERN” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN

    2 Nov 2018
    Ana Lopes

    CERN ALPHA-g experiment being installed at CERN_s Antiproton Decelerator hall. (Image CERN)

    CERN ALPHA-g Detector

    We learn it at high school: Release two objects of different mass in the absence of friction forces and they fall down at the same rate in Earth’s gravity. What we haven’t learned, because it hasn’t been directly measured in experiments, is whether antimatter falls down at the same rate as ordinary matter or if it might behave differently. Two new experiments at CERN, ALPHA-g and GBAR, have now started their journey towards answering this question.


    CERN GBAR

    ALPHA-g is very similar to the ALPHA experiment [below], which makes neutral antihydrogen atoms by taking antiprotons from the Antiproton Decelerator (AD) and binding them with positrons from a sodium-22 source. ALPHA then confines the resulting neutral antihydrogen atoms in a magnetic trap and shines laser light or microwaves onto them to measure their internal structure. The ALPHA-g experiment has the same type of antiatom making and trapping apparatus except that it is oriented vertically. With this vertical set-up, researchers can measure precisely the vertical positions at which the antihydrogen atoms annihilate with normal matter once they switch off the trap’s magnetic field and the atoms are under the sole influence of gravity. The values of these positions will allow them to measure the effect of gravity on the antiatoms.

    The GBAR experiment, also located in the AD hall, takes a different tack. It plans to use antiprotons supplied by the ELENA deceleration ring and positrons produced by a small linear accelerator to make antihydrogen ions, consisting of one antiproton and two positrons. Next, after trapping the antihydrogen ions and chilling them to an ultralow temperature (about 10 microkelvin), it will use laser light to strip them of one positron, turning them into neutral antiatoms. At this point, the neutral antiatoms will be released from the trap and allowed to fall from a height of 20 centimetres, during which the researchers will monitor their behaviour.

    After months of round-the-clock work by researchers and engineers to put together the experiments, ALPHA-g and GBAR have received the first beams of antiprotons, marking the beginning of both experiments. ALPHA-g began taking beam on 30 October, after receiving the necessary safety approvals. ELENA sent its first beam to GBAR on 20 July, and since then the decelerator and GBAR researchers have been trying to perfect the delivery of the beam. The ALPHA-g and GBAR teams are now racing to commission their experiments before CERN’s accelerators shut down in a few weeks for a two-year period of maintenance work. Jeffrey Hangst, spokesperson of the ALPHA experiments, says: “We are hoping that we’ll get the chance to make the first gravity measurements with antimatter, but it’s a race against time.” Patrice Pérez, spokesperson of GBAR, says: “The GBAR experiment is using an entirely new apparatus and an antiproton beam still in its commissioning phase. We hope to produce antihydrogen this year and are working towards being ready to measure the gravitational effects on antimatter when the antiprotons are back in 2021.”

    Another experiment at the AD hall, AEgIS, which has been in operation for several years, is also working towards measuring the effect of gravity on antihydrogen using yet another approach. Like GBAR, AEgIS [below] is also hoping to produce its first antihydrogen atoms this year.

    Discovering any difference between the behaviour of antimatter and matter in connection with gravity could point to a quantum theory of gravity and perhaps cast light on why the universe seems to be made of matter rather than antimatter.

    See the full article here.


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    Meet CERN in a variety of places:

    Quantum Diaries
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    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Grand Tunnel

    CERN LHC particles

    OTHER PROJECTS AT CERN

    CERN AEGIS

    CERN ALPHA

    CERN ALPHA

    CERN AMS

    CERN ACACUSA

    CERN ASACUSA

    CERN ATRAP

    CERN ATRAP

    CERN AWAKE

    CERN AWAKE

    CERN CAST

    CERN CAST Axion Solar Telescope

    CERN CLOUD

    CERN CLOUD

    CERN COMPASS

    CERN COMPASS

    CERN DIRAC

    CERN DIRAC

    CERN GBAR

    CERN GBAR

    CERN ISOLDE

    CERN ISOLDE

    CERN LHCf

    CERN LHCf

    CERN NA62

    CERN NA62

    CERN NTOF

    CERN TOTEM

    CERN UA9

    CERN Proto Dune

    CERN Proto Dune

     
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