Physicists chip away at mystery of antimatter imbalance
Two types of neutron decay produce a proton, an electron and an electron antineutrino but eject them in different configurations, The experiments at NIST detected no imbalance, but the improved sensitivity could help place limits on competing theories about the matter-antimatter imbalance in the universe. Credit: emiT team
(PhysOrg.com) -- Why there is stuff in the universe—more properly, why there is an imbalance between matter and antimatter—is one of the long-standing mysteries of cosmology. A team of researchers working at the National Institute of Standards and Technology has just concluded a 10-year-long study of the fate of neutrons in an attempt to resolve the question, the most sensitive such measurement ever made. The universe, they concede, has managed to keep its secret for the time being, but they’ve succeeded in significantly narrowing the number of possible answers.
Though the word itself evokes science fiction, antimatter is an ordinary—if highly uncommon—material that cosmologists believe once made up almost exactly half of the substance of the universe. When particles and their antiparticles come into contact, they instantly annihilate one another in a flash of light. Billions of years ago, most of the matter and all of the antimatter vanished in this fashion, leaving behind a tiny bit of matter awash in cosmic energy. What we see around us today, from stars to rocks to living things, is made up of that excess matter, which survived because a bit more of it existed.
“The question is, why was there an excess of one over the other in the first place?” says Pieter Mumm, a physicist at NIST’s Physical Measurements Lab. “There are lots of theories attempting to explain the imbalance, but there’s no experimental evidence to show that any of them can account for it. It’s a huge mystery on the level of asking why the universe is here. Accepted physics can’t explain it.”
Physicists including Pieter Mumm (shown) used the emiT detector they built at NIST to investigate any potential statistical imbalance between the two natural types of neutron decay. Credit: emiT team
An answer might be found by examining radioactivity in neutrons, which decay in two different ways that can be distinguished by a specially configured detector. Though all observations thus far have invariably shown these two ways occur with equal frequency in nature, finding a slight imbalance between the two would imply that nature favors conditions that would create a bit more matter than antimatter, resulting in the universe we recognize.Mumm and his collaborators from several institutions used a detector at the NIST Center for Neutron Research to explore this aspect of neutron decay with greater sensitivity than was ever possible before. For the moment, the larger answer has eluded them—several years of observation and data analysis once again turned up no imbalance between the two decay paths. But the improved sensitivity of their approach means that they can severely limit some of the numerous theories about the universe’s matter-antimatter imbalance, and with future improvements to the detector, their approach may help constrain the possibilities far more dramatically.
“We have placed very tight constraints on what these theories can say,” Mumm says. “We have given theory something to work with. And if we can modify our detector successfully, we can envision limiting large classes of theories. It will help ensure the physics community avoids traveling down blind alleys.”
The research team also includes scientists from the University of Washington, the University of Michigan, the University of California at Berkeley, the University of Notre Dame, Hamilton College and the University of North Carolina at Chapel Hill. Funding was provided by the U.S. Department of Energy and the National Science Foundation.
More information: H.P. Mumm, T.E. Chupp, R.L. Cooper, K.P. Coulter, S.J. Freedman, B.K. Fujikawa, A. García, G.L. Jones, J.S. Nico, A.K. Thompson, C.A. Trull, J.F. Wilkerson and F.E. Wietfeldt. New limit on time-reversal violation in beta decay. Physical Review Letters, Vol. 107, Issue 10, DOI: 10.1103/PhysRevLett.107.102301
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National Institute of Standards and Technology
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Nov 09, 2011
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This is unfortunately sheer speculation since there is no evidence to support this, only MORE unsubstantiated speculation. No one was there to observe and record it and this 10-yr research did nothing2change that lack.
The mystery of why there's matter and not the same amount of anti matter around is similar to why living organisms display such an intolerably inexplicable preference for chirality at the molecular level. The two phenomena have exactly the same common characteristic: Eneergy transformation produces both matter and anti-matter - without exception whilst similarly organic chemical reactions tend to produce both left-and right-handed isomers in equal quantities.
So there's no explanation for how matter can exist naturally and also how organic life can contain proteins/enzymes/dna made up of single-handed isomer
Nov 09, 2011
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Nov 09, 2011
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Nov 09, 2011
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Nov 09, 2011
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Because we don't know yet whether matter and antimatter gravitational attract, or repel. Like most people I had assumed that they must attract, and there are a number of sound arguments for that assumption - but it turns out that those arguments are all unproven.
Until we answer that question experimentally, it's possible that there are an equal number of antimatter galaxy clusters in the universe gravitationally repelling matter galaxy clusters. This would neatly resolve the "annihilation catastrophe" problem, and also offer an intriguing new explanation of dark energy.
We should know soon. Antimatter containment is *almost* advanced enough to test the idea in the lab, and the Alpha Magnetic Spectrometer is looking for an anti-alpha particle (finding just one would prove the existence of antimatter stars in the universe: http://ams.nasa.g...t.html).
Nov 09, 2011
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http://arxiv.org/abs/0804.4199
http://arxiv.org/.../0610079
http://arxiv.org/abs/1103.4937
http://arxiv.org/.../9906012
http://en.wikiped...timatter
Nov 09, 2011
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http://public.web...3-a.html
http://science.na...aug_ams/
http://www.nature...260.html
Nov 09, 2011
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Recent Progress in Chirality Research Using Circularly Polarized Light
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Nov 09, 2011
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Nov 10, 2011
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Nov 10, 2011
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Nov 10, 2011
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I think in terms of matter as being compressed regions of spacetime and anti-matter expanded regions instead of positive and negative curvature but it's essentially the same. Compression results in stretching neighboring spacetime toward the compressed elements, hence gravity. Similar idea for antimatter - expanded elements of spacetime. However in regions of denser spacetime expanded elements are repulsed - hence anti-gravity. The net effect is matter/antimatter repulsion mediated by spacetime.
Point being antimatter is repulsed to the outer regions of spacetime. The second point is antimatter is mutually repulsive when mediated by spacetime. That is intervening spacetime repels antimatter. Hence I don't expect to see galaxies or any cosmic bodies of antimatter formed.
Nov 10, 2011
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The implications seem important for a cyclic universe theory. Antimatter accumulates in an outer shell of spacetime, matter in an inner shell, spacetime mediating the separation of the two shells. However when the dark energy runs out, the accelerated expansion stops. Spacetime could continue to expand at a constant velocity, but the electrostatic force between the positrons in the outer shell and electrons in the inner shell stops expansion and starts compression where the potential energy of expansion is returned to the internal DE of spacetime. Eventually the electrostatic forces overcome the repulsive gravitational forces and the two shells merge together, resulting in a bolt of lightning like in a double-barreled van de Graf generator resulting in the inflationary phase of expansion. Roger Penrose claims to see images of circles in the CMBR, which could be these two shells.
More discussions at http://www.physor...ory.html
Nov 10, 2011
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Note particles in the inner and outer shells, being mutually repulsive, assure symmetric (or very nearly so) configurations.
Nov 12, 2011
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Note in your references I see no consideration of the mediating effects of spacetime on matter and anti-matter. That is matter and antimatter don't normally interact gravitationally in the absence of spacetime, hence mesons can exist for short times until spacetime intervenes and subjects the matter particle to gravity and the antimatter particle to anti-gravity.
Nov 14, 2011
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So my question is at what distance does the force of gravity between 2 electrons counter-balance the electrostatic force of repulsion? Obviously I'm thinking about a stable configuration for the inner shell of electrons.
It may be a moot question if the Planck constant changes with time. That is when the dark energy is converted to electrostatic attraction between the inner and outer shells do quantum fluctuations and perhaps the Planck constant cease to exist? In that case spacetime and something like a singularity might actually occur.
Nov 14, 2011
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Note if the Planck constant changes with time redshift values and age of the universe calculations would be affected.
Nov 14, 2011
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A U with 0 Planck constant would be a pretty dark place - no radiation. With nothing to fuel the uncertainty principle spacetime would become deterministic and collapse, at least untill the collapse of the outer shell, when the stored electrostatic energy is again released as radiation.
Nov 15, 2011
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Nov 15, 2011
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Munchhausen syndrome.
Nov 18, 2011
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Well maybe psycobabble is easier to understand in small chuncks. Like if the Planck "constant" changes over time as the dark energy runs out it would be one of those inconvenient truth issues. That is redshifts and the age of the universe would have to be recalculated. Sorry.
Nov 20, 2011
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Nov 22, 2011
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When the DE, or internal energy of spacetime is greater than 0, elements of spacetime undergo random quantum fluctuations in size and shape. Suppose at any specific time all elements have a fixed energy, so quantum fluctuations only cause various energy densities. If the fluctuation falls into an allowed quantum state it can assume the energy density of that state. The actual fluctuation is random but the quantum states are discrete. So any residual energy after formation of the quantum state is released as radiation.
Nov 22, 2011
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Note the definitions involve the idea of normal, that is what appears to be undistorted spacetime. So whether it's elements of matter or anti-matter depends on what you call normal. As spacial expansion continues and the DE runs out, normal will become less and less dense. When it reaches the density of antimatter the antimatter dissolves into spacetime. So as normal becomes less dense the distribution of matter and anti-matter, as it is observed relative to undistorted spacetime, changes. CP violation should appear to increase as expansion continues.
Nov 22, 2011
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Black holes eventually evaporate and antimatter is dissolved in spacetime expansion, leaving spacetime with an outer shell of positrons and an inner cloud of electrons. DE is now transformed into electrostatic potential energy of the electrons and positrons. Spacetime has essentially become a huge supercharged battery. Electrostatic attraction takes over and accelerating particles radiate, raising the temperature of spacetime. No new quark matter is created in the collapsing phase because that requires condensation which can't happen as spacetime temperature rises. When the charges meet the currents really start to flow and the next BB comes in like a giant stroke of lightening. Or so it appears here in Lake Wobegon.
Nov 24, 2011
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Dec 09, 2011
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The universe expands in opposite directions in space. I wonder if it does the same thing in time. Like we experience time running forwards and in reverse. The present time thus has a double meaning - present in forward and reverse time.