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For Symmetry Magazine:
We live in a world full of matter: stars made of matter, planets made of matter, pizza made of matter. But why is there pizza made of matter rather than pizza made of antimatter or, indeed, no pizza at all?
In the first split-second after the big bang, the universe made a smidgen more matter than antimatter. Instead of matter and antimatter annihilating one another and leaving an empty, cold universe, we ended up with a surplus of stuff. Now scientists need the most sensitive detectors and mountains of experimental data to understand where that imbalance comes from.
Belle II is one of those detectors that will look for differences between matter and antimatter to explain why we’re here at all. Currently under construction, the 7.5-meter-long detector will be installed in the newly recommissioned SuperKEKB particle accelerator located in Tsukuba, Japan. SuperKEKB runs beams of electrons and positrons (the antimatter version of electrons) into each other at close to the speed of light, and Belle II—once it is fully operational in 2018—will analyze the detritus of the collisions. [Read the rest at Symmetry Magazine…]
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From NOVA Nature of Reality:
There are two kinds of matter in the universe: ordinary matter, which makes up all the stuff of everyday life, and antimatter, a sort of mirror image of matter. When the two meet, they annihilate in a flash of energy. It’s our good fortune that, in the early Universe, there was just a tiny bit more matter than antimatter, leaving us with a cosmos almost empty of stuff that could destroy us. Otherwise, we wouldn’t be here to ask what, exactly, antimatter is.
Here’s what we know: Anti-electrons, known as positrons, are nearly identical to electrons, but instead of being negatively charged they are positively charged. The same goes for other antimatter counterparts: antiprotons are negatively charged and made of the antiquarks corresponding to the quarks in normal protons.
But physicists think that the other properties of the particles should be the same. [Read more at NOVA…]
Gravity is a universally attractive force, at least as far as we can tell. However, some physicists have posited that antimatter behaves the opposite way, as though they have negative mass. Testing that hypothesis is remarkably hard, though: antimatter particles annihilate with their regular matter partners if they encounter each other (at low speeds at least), and gravity is by far the weakest force in the Universe. As a result, we can’t make a big weight out of antimatter and drop it. So, researchers at CERN have proposed another way, using the existing ALPHA experiment designed to trap anti-hydrogen. While preliminary results can’t answer whether antimatter possesses antigravity, the experiment itself is promising.
How deep does the asymmetry between matter and antimatter go? Each type of particle (electrons, protons, etc.) have antimatter partners: positrons, antiprotons, and so forth. These antiparticles have an opposite electric charge (unless they’re neutral), but otherwise behave much like their matter counterparts. But one interesting question remains unanswered: does antimatter possess antigravity, experiencing a repulsive force when matter experiences attraction? And, even if antimatter experiences plain old gravity, does it behave in exactly the same way as matter does?
Researchers from the ALPHA experiment at CERN realized their antihydrogen trap could help answer that question. [Read more…]