ALPHA Closes in on Antimatter

Article written: 10 Mar , 2012
Updated: 26 Apr , 2016


We live in a universe made of matter. But at the moment of the Big Bang, matter and antimatter existed in equal amounts. That antimatter has all but disappeared suggests that nature, for some reason, has a strong preference for matter. Physicists want to know why matter has replaced its antimatter twin, and this week the ALPHA collaboration at CERN got a step closer to unraveling the mystery. 

ALPHA, an international collaborative experiment established in 2005, was designed to trap and measure antihydrogen particles with a specially designed experiment. It’s picking up where its antimatter-searching predecessor, ATHENA, left off. The focus is on antihydrogen because hydrogen is the most prevalent element in the universe and its structure is extremely well known to scientists.

Each hydrogen atom has one electron orbiting its nucleus. Firing light at the atoms excites the electron, causing it to jump into an orbit further away from the nucleus before it relaxes and returns to its resting orbit emitting light in the process. The frequency distribution of this emitted light is known; it has been precisely measured and, in our universe made of matter, is unique to hydrogen.

An illustration of hydrogen and antihydrogen. Credit: USAF

Basic physics dictates that hydrogen’s antimatter twin, antihydrogen, should be equally recognizable by having an identical spectrum. That is, if everything we know about particle physics is right. Capturing and measuring antihydrogen’s spectrum is the main goal of the ALPHA group.

ALPHA has taken the first modest measurements of antihydrogen. In the ALPHA apparatus, antihydrogen is trapped by an arrangement of magnets that affect the magnetic field of the atoms. Microwaves tuned to a specific frequency aimed on these antihydrogen atoms flips their magnetic orientation, liberating them. The freed antihydrogen meets hydrogen as it escapes and the two annihilate one another, leaving a well known pattern in particle detectors surrounding the apparatus.

The apparatus captured evidence of the electron jumping orbits in an antihydrogen atom after microwave radiation changed its internal state. The result further proves the validity of ALPHA’s approach, demonstrating that the apparatus has enough control and sensitivity to successfully carry out the experiment it was designed for. In the future, ALPHA will focus on improving the precision of its microwave measurements to uncover the antihydrogen spectrum using lasers.

The exciting results were hard to come by as antihydrogen does not exist in nature. It’s made in the ALPHA apparatus from antiprotons that are themselves made in the Antiproton Decelerator and positrons from a radioactive source. And it has to have a low enough energy level to stay trapped for measurements. But it’s working, and it just might give physicists the key they need to understand the mystery of the early universe.

Source: CERN

19 Responses

  1. JiveDance says

    “The focus is on antihydrogen because hydrogen is the most prevalent element in the universe and its structure is extremely well known to scientists.”

    The focus is on antihydrogen because nobody knows how to capture anti-neutrons to create anything heavier!

    • Torbjörn Larsson says

      Yes, but then again it is lucky and worth noting that this element is the most interesting here (early important, most important, easy to observe).

      I have already voiced grave concerns about the imagery used in this article, so I would like to let this mistaken implication based on the press release material slip by. It is a minor matter.

      (But I do note, IVAn3MAN style, that the ALPHA work has two focuses, this and a focus on “improving the precision”. I have days like that too, a term keeps coming back all over the place. :-/)

  2. lcrowell says

    The question about CP violations is very deep. To be honest I think this has some connection to issues with gravity. The CPT theorem tells us that if you flip the charge by applying C and then flip the parity by applying P and the reverse the time direction by applying T you get one CPT = 1. Therefore CPTT = T and T^2 = 1 — reverse time twice to get the same direction. So a reversal of C and P is a time reversal. This discrete symmetry group called the CPT theorem tells us that if CP symmetry if violated then T symmetry is violated as well. This would then tell us that the universe has a preferred direction in time. However, the amount of entropy generated by CP violations is tiny compared to the thermodynamic “arrow of time” in our observable universe.

    So if there is a connection with a cosmic time asymmetry it must involve something deeper. One suggestion is that QCD of quarks and their gauge boson called the gluon has some CP violation as well. This is carried in a particle called the axion. The QCD field has a structure which is holographically related to or equivalent to the graviton. This is the AdS_3 ~ QCD correspondence, which is a subset of the AdS (anti-de Sitter spacetime) correspondence to conformal quantum field theories. The universe appears to have two main partitions, one which involves gravity and QCD, and the other is the weak and electromagnetic interaction with an isometry that is formally the same as QCD. We have CP violations in this latter half, which may then be mirrored in the first half with QCD and gravity.

    The particle physics interest in CP violations is with T and T-bar and B and B-bar physics with these quarks and their antimatter equivalents. Parity violations of these quarks is an active aspect of research. The meson formed by (T-T-bar) or (B-B-bar) will then not be entirely diagonalizable within the QCD Hamiltonian, but have off diagonal parts due to CP violations. This is a form of the K-K-bar problem back in the 1960s.

    When it comes to hydrogen and anti-hydrogen I would expect the two to be indistinguishable according to the electromagnetic or QED interaction. CP violations will be observable only if subtle weak interactions occur. The electron in a hydrogen atom does have a tiny quantum amplitude for existing in the nucleus, where there will be some weak interaction physics. This is very small though.

    I could break this out in greater detail to give some idea of how the axion is related to the graviton. However, that will require my writing a fair amount of a^†_n, a_n stuff in quantum mechanics.


  3. LeslieJohnnson says

    The best things in life are free

  4. proton is normally positive in nature. Proton made up of positive and negative by system. The percentage of negative is less than that of positive. In what way the antimatter can for that is written in my book “Mystery of the world of atom” (1986). The book is kept in The
    Library, The Abdus Salam International Centre … , London and for reference one. And in
    ( 15. Das, Nirmalendu
    Mystery of the word atom / by Nirmalendu Das.– Sikkim:
    Mukul das, 1986. 116p.
    539.72 N861 G19282
    In what way the matter and antimatter can be formed, that forming is very interesting.
    Nirmalendu Das.
    Dated: 10-03-2012.

    • Olaf2 says

      What do you mean exactly with the percentage of negative is less than the positive?
      Less mass? Less charge?

      What do you mean exactly with Proton made up of positive and negative by system?
      Charge mass, particles?

    • ren00r says

      I’m also very interested in “what way the antimatter can for”

  5. Torbjörn Larsson says

    I’m fairly agnostic on measuring antimatter properties, since it has a long and illustrious history from ideas of “antigravity” to these kinds of measurements. Maybe they will help, maybe not.

    However, these recent results on unexpected CP symmetry breaking gets me excited. The Standard Model has some, but I gather it isn’t enough to explain the matter excess. Maybe LC can why some parts of percent lifetimes wouldn’t bootstrap up to the necessary 10^-6 or so difference between surviving matter and annihilated antimatter.

    The chinese-international experiment in Daya Bay however, shows that the neutrino sector, which isn’t in the SM model, has high CP antisymmetry. So high in fact, that the experiment picked it up despite not being completely finished. Maybe this will explain matter-antimatter.

    Now to a more serious nitpick. Since it is that, I will have to start with noting that I am a huge fan of Teitel’s space history articles and have said so over at her blog. So please don’t take this personal, despite I believe this is the 2nd article in a row I nitpick.

    The illustration is ill chosen. The best I can say about it is that reminds of the “primordial” Alfvén cosmology, where heterogeneous matter/anti-matter regions battled it out. No radiation from such interactions regions were ever found.

    Today the standard cosmology predicts that structure formation starts with quantum fluctuation in the inflating volume. Matter and antimatter is created later and in equal amounts during reheating of the inflationary supercooled volume. This is then sorted out by annihilation and later gravitational assembly, or so I take it.

    This ironically becomes space history, what is the story behind the illustrations? They probably stem from this UT article on matter/antimatter annihilation, where they illustrate “Matter”. Oops! The original source material, if not illustration, is on the Bullet Cluster formation.

    I have been unable to track the image source, but this is another artist illustration of the same structure. The two clusters are tracking the dark matter concentration, the two gas fans are where the most ordinary mass is because of its self-interactions. The correct caption would be something like:

    “What matter and dark matter might look like after a collision.”

    What matter and antimatter looked like under annihilation was probably more like an energetic homogeneous broth, where baryonic and dark matter particles diluted to be mostly replaced by radiation.

  6. parvenu says

    The question of what happened to anti-matter from the “Big Bang” is derived from the assumption that we (humans) can observe virtually everything in the universe. Based on our rate of development of instrumentation that can at best infer or imply the existence or non-existence of physical entities about which we theorize, we as a phenomenon evolve comensurate with the effectivity and reliability of our instrumentation.

    I submit that infinite forms of energy exist throughout the Universe bounded and undetected by mankind. Whereas mankind must initially conceive of some unique energy form, then convert these imaginings into postulations and theories, establish some measure of feasible proof, devise experimental test manipulations for the purpose of securing acceptable observable data, the information from which can finally be used to create acceptible reliable instrumentation to unitize and manipulate this one uniquely peculiar energy form.

    If you accept the Big Bang was the initial rapid start of the immediate expansion and distribution of energy throughout space; then you must agree to consider that in that incredibly minute instant of time that no constraints existed to limit the formulation of the expanding energy to any set of random forms. Therefore the Universal set of every possible unique energy form is likewise infinite.

    Considering that there are infinite energy forms in our Universe, pretty much all of which are beyond our imagination, not to mention our comprehension, we will be at this longer than we have time available to exist in our own unique energy form.

    • lcrowell says

      There can’t be any antimatter region of the universe out to the CMB limit. If there were the spectral lines of e-e^+ and p-p^- annihilations would stick out like a sore thumb. The contact point between the two regions would have massive amounts of gamma radiation with that mass-energy signature. The region beyond the CMB, say about 45 billion light years out is harder to talk about, for if there are such region or a contact between our region and an antimatter region that extends out that far the radiation would likely be thermalized into the radiation dominated plasma of that epoch in cosmic evolution. As you get to around a trillion light years out there might exist the boundary between our bubble nucleation region or pocket universe and the region of inflationary expansion. That inflationary expansion may though have ended. So the universe may have these island universes generated from bubble nucleation, where some of these could turn out to be anti-matter regions. However, these regions may simply be far too distant for us to get any information from.


    • David Krauss says

      Science might never run out of things to investigate. That would also mean that technological progress could never stop. Doesn’t sound like a reason to give up!

  7. For the love of God, my head hurts now. LC, is there any quantum mechanics that can make me an alkaseltzer after reading all of these comments?

    On the serious side, the ability to manufacture antimatter in any form is absolutely amazing! I just wish I understood it as well as you all seem to. Very interesting article.

  8. Rootdown says

    OK, anti-matter is seriously the way to take humans to the next level!

  9. Mastercope says

    The truth is the Hand of God swept away most of the Antimatter,, That’s why we are still here.

    And now the fight starts

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  11. Member
    Aqua4U says

    Tip of the iceberg anyone? Obviously what we see in our physical universe is not all there is. An inherent myopia? Parallel universe(s) or the multiverse theory comes to mind here.

    I very much like Icrowell’s comment about reversing the direction of time. Time being the 4th dimension and all – at least locally. Sparks the mind into thinking how parallel universes might interact, if they do at all, given they may have dissimilar timelines – slower, faster or opposing, with gravity being key? Hmm… In a reversed time line parallel, might anti-matter rule?

    Yeah… when thinking about all this I look in the mirror and I see smoke and sparks coming out of my ears . My intuitive side says… there are more answers than questions and we’re getting closer to the truth every day. Hopefully we’ll last long enough to know? Inquiring minds want to know. And isn’t that the first part of discovery?

    • wjwbudro says

      “Hmm… In a reversed time line parallel, might anti-matter rule? ”

      If so we better hope that we share the same geometric rules.

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