The heaviest known antimatter

Feb 14, 2011
The diagram above is known as the 3-D chart of the nuclides. The familiar Periodic Table arranges the elements according to their atomic number, Z, which determines the chemical properties of each element. Physicists are also concerned with the N axis, which gives the number of neutrons in the nucleus. The third axis represents strangeness, S, which is zero for all naturally occurring matter, but could be non-zero in the core of collapsed stars. Antinuclei lie at negative Z and N in the above chart, and the newly discovered antinucleus (magenta) now extends the 3-D chart into the new region of strange antimatter.

When an international team of scientists working at the Relativistic Heavy Ion Collider (RHIC) announced the discovery of the most massive antinucleus to date — and the first containing an anti-strange quark — it marked the first entry below the plane of the classic Periodic Table of Elements, and sparked enormous interest worldwide. Dr. Zhangbu Xu, a physicist at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, where the 2.4-mile circular “atom smasher” is located, will share this discovery with a wider audience at this year’s meeting of the American Association for the Advancement of Science (AAAS) on Friday, February 18, 2011.

All ordinary nuclei are made of protons and neutrons (which in turn contain only up and down ). The standard Periodic Table of Elements is arranged according to the number of protons, which determine each element’s chemical properties. There is also a more complex, three-dimensional chart that conveys information about the number of neutrons, which may change in different isotopes of the same element, and a quantum number known as “strangeness,” which depends on the presence of strange quarks. Nuclei containing one or more strange quarks are called hypernuclei. For all ordinary matter, with no strange quarks, the strangeness value is zero and the chart is flat. Hypernuclei appear above the plane of the chart.

Last year, members of the STAR detector collaboration at RHIC published evidence of a form of strange antimatter with an anti-strange quark — an antihypernucleus — making it the first entry below the plane of the 3D chart of nuclides, laying the first stake in a new frontier of physics.

Collisions at RHIC fleetingly produce conditions that existed a few microseconds after the Big Bang, which scientists believe gave birth to the universe as we know it some 13.7 billion years ago. In both nucleus-nucleus collisions at RHIC and in the Big Bang, quarks and antiquarks emerge with equal abundance. Nuclear collisions are unique and distinct from elementary particle collisions because they deposit large amounts of energy into a more extended volume. In contrast to the Big Bang, the small amount of energy in nuclear collisions produces negligible gravitational attraction, which allows the resulting quark-gluon plasma to expand rapidly and to cool down and transition into a hadron gas, producing nucleons and their antiparticles.

At RHIC, among the collision fragments that survive to the final state, matter and antimatter are still close to equally abundant, even in the case of the relatively complex antinucleus and its normal-matter partner featured in the present study. In contrast, antimatter appears to be largely absent from the present-day universe.

The STAR team has found that the rate at which their heaviest antinucleus is produced is consistent with expectations based on a statistical collection of antiquarks from the soup of quarks and antiquarks generated in RHIC collisions. Extrapolating from this result, the experimenters believe they should be able to discover even heavier antinuclei in upcoming collider running periods. The most abundantly produced antimatter next in line for discovery is the antimatter Helium-4 nucleus, also known as the antimatter α (alpha) particle.

Dr. Xu, a member of the STAR collaboration, will describe the discovery of the first antimatter hypernucleus, the models which can describe the production mechanism and the abundance of these antimatter nuclei, and the remaining heaviest nucleus to be discovered in the foreseeable future at RHIC.

The STAR collaboration is composed of 54 institutions from 13 countries. Research at RHIC is funded primarily by the U.S. Department of Energy’s Office of Science, Office of Nuclear Physics, and by various national and international collaborating institutions.

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geokstr
2.3 / 5 (3) Feb 14, 2011
Perhaps someone who knows the math can answer this.

I've often heard it said that the laws of physics not only do not preclude the existence of anti-matter, but instead actually demand it. Then the theory must be twisted in all sorts of ways to show why we don't find any anti-matter in nature anymore, if it was made in nearly equal amounts in the Bang. The only place we've been able to find any is in the super-colliders, and only in highly insignificant amounts.

Shouldn't extreme natural events like supernova also form significant amounts of anti-matter?

Is it possible that, despite what the math says (so far) that the basic laws of physics do NOT allow for anti-matter to form naturally, and our math is just not yet developed enough to show that?
bugmenot23
3 / 5 (2) Feb 14, 2011
Not math, physics.

The physics you are referring to is the standard model, which would indicate that there should be equal quantities of both matter and anti-matter.

There are other proposed physics models that would explain the asymmetry of matter and anti-matter.
However they are only proposals and have not been tested/confirmed as yet.
geokstr
1 / 5 (1) Feb 14, 2011
Isn't theoretical physics, including the "standard model" mostly based on math, like GR & SR, for examples? And the lack of anti-matter in nature would have to be explained with theoretical physics, non, since it's a bit difficult to find any in the real world?

Of course the math would need to be checked against physical observations and predictions, but it's still math, specialized for physics.

You would think that under even the standard model, the initial annihilation of anti-matter would still have left some pockets where it dominated, like maybe whole galaxies here and there, but none have ever been found.
kaasinees
not rated yet Feb 14, 2011
Where is the evidence of anti-matter?
Parsec
4.8 / 5 (5) Feb 14, 2011
Where is the evidence of anti-matter?

Quite simply, particles have a set of properties, one of which is mass, the other is charge. If we see a particle with all of the properties of an electron, except that it is positively charged, that is evidence of a anti-electron (positron). Similarly for the anti-proton, etc.

@geokstr - Most physicists now believe that CP violations are the reason why we see matter and not anti-matter in the universe.

Saying that physics is 'based on math' is like saying that race-car driving is based on math. Both are true and equally meaningless in the context you quoted.
Ronan
5 / 5 (3) Feb 14, 2011
Antimatter isn't just an artificial, human-made thing; there are all sorts of examples of natural sources of antimatter. Positron emission in radioactive decay is probably the example that's closest to home, but there are also bursts of antimatter released by thunderstorms (not enough to be noticeable if you aren't looking for it with the right instruments, but still there), antimatter produced by the collision of cosmic rays with molecules high up in our atmosphere, and of course there's antimatter released by violent stellar events, as well; gamma ray bursts, supernovae, etc. The reason why we don't get much antimatter out of said astronomical cataclysms is that even at those energies, the conditions required to actually create new matter out of energy (which is what would give you a particle-antiparticle pair) just aren't that likely. Mostly, you just end up with a cloud of superheated plasma.

...But that aside, very interesting paper! Now, for low-temperature antiparticles...
Mendeleev
1 / 5 (1) Feb 14, 2011
For more on the periodic table of the elements please see the book,

Eric Scerri, The Periodic Table, Its Story and Its Significance, Oxford University Press, 2007
kaasinees
not rated yet Feb 14, 2011
Thank you fore the info Ronan & Parsec.
What happens to these anti-matter particles? And does it really make sense to call a positron anti-matter, instead of an exotic particle? Just like isotopes with fast half-lifes, unbalanced and in un undesirable place where they turn into something else.
TechnoPagan
5 / 5 (2) Feb 15, 2011
Thank you fore the info Ronan & Parsec.
What happens to these anti-matter particles? And does it really make sense to call a positron anti-matter, instead of an exotic particle? Just like isotopes with fast half-lifes, unbalanced and in un undesirable place where they turn into something else.


Shortly after their creation, positrons will collide with electrons, annihilating each other releasing energy. I don't know a better way to say "anti-matter".
Aristoteles
not rated yet Feb 15, 2011
Why not lightest ? Do antimatter "anti-falling" ?
Is there DARK ANTI-MATTER ? ( dark energy radiation -
DARKON, a quantum of dark-AdS-geometry...)
frajo
not rated yet Feb 15, 2011
And does it really make sense to call a positron anti-matter, instead of an exotic particle?
It's not so exotic anymore.
Read Wikipedia on "Positron emission tomography":
The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.
...
It is used heavily in clinical oncology (medical imaging of tumors and the search for metastases), and for clinical diagnosis of certain diffuse brain diseases such as those causing various types of dementias. PET is also an important research tool to map normal human brain and heart function.
dav_i
not rated yet Feb 16, 2011
Do antimatter "anti-falling" ?


If by this you mean "Does antimatter fall upwards?" then the answer is no.
Antimatter has opposite electrical charge and spin but does not have opposite mass.

Objectivist
not rated yet Feb 17, 2011
Perhaps someone who knows the math can answer this.

I've often heard it said that the laws of physics not only do not preclude the existence of anti-matter, but instead actually demand it. Then the theory must be twisted in all sorts of ways to show why we don't find any anti-matter in nature anymore, if it was made in nearly equal amounts in the Bang. The only place we've been able to find any is in the super-colliders, and only in highly insignificant amounts.

Shouldn't extreme natural events like supernova also form significant amounts of anti-matter?

Is it possible that, despite what the math says (so far) that the basic laws of physics do NOT allow for anti-matter to form naturally, and our math is just not yet developed enough to show that?
Short answer: the relation between matter and antimatter is not completely symmetrical. Long answer: check out the 2008 Nobel prize awards in physics.
Ronan
not rated yet Feb 21, 2011
Dav i: As an interesting addendum to your post, I'd like to point out that although antiparticles certainly have the same mass as their pair particle, it has never been conclusively established that that mass responds to a gravitational field the same way that normal matter does. I could be wrong in my interpretation of what I've read on this subject, but I gather that it's still a possibility, albeit a somewhat slim one, that antiparticles behave normally in terms of their inertia, but would exhibit antigravitational properties (more specifically, they'd be repelled by normal matter and attracted to other antimatter).