Antimatter

The standard model is dear to physicists because it has unified our understanding of the microworld, successfully predicted new particles, and most important, has never been directly contradicted by experiment. But the standard model suffers from a major glitch-namely, the matter-antimatter conundrum-and physicists are striving to discover how, and precisely where, it's wrong, or at least incomplete. "It's the place where the standard model hasn't really been tested," concedes Helen Quinn, theorist at SLAC and vice president of the American Physical Society.


The holy grail in this quest is CP violation, a phenomenon that implies that antimatter is not matter's perfect mirror image, as it's generally thought to be. If the two sometimes behave differently, that nonconformity would help explain why the world around us exists. The standard model predicts some CP violation-and in a landmark finding last summer, the team at SLAC uncovered roughly that amount. But the CP violation predicted by the standard model is not nearly enough to explain the vast amounts of matter in the universe.


So physicists are searching for more CP violation in two very different ways. Experimental groups have designed giant, costly trials (a large portion of SLAC's $184 million annual budget, as well as many more millions in grant money awarded to affiliated researchers at 72 institutions, goes toward the antimatter experiment). These researchers hope that their accelerators will ultimately reveal inconsistencies in the standard model-loopholes, if you will. Meanwhile, another sort of physicist, equipped only with a PC, some mathematical theorems, and lots of time to think, is taking a different approach. Members of this group want to extend the standard model-in effect, to change it. They are trying to create a new physics, and antimatter is their guide.


BACK TO THE BIG BANG

If matter is the everyday stuff of the universe, then one might assume that antimatter is its opposite. That's not the case. Antimatter is almost exactly the same as matter, with just a few key properties reversed. The antiproton, for example, the antimatter equivalent of the proton, is identical to the proton except that it has a negative instead of a positive charge. Yet matter and antimatter have an incendiary relationship: When they meet, both are destroyed in a violent burst of light and energy.


To understand the problem this creates, you have to start from the beginning-the big bang. The universe was born 15 billion years ago as an infinitesimally tiny point of energy. We usually think of the universe in terms of stars and galaxies and impossibly huge regions of nothingness in between, but the young universe was a very different place. All the countless galaxies that exist today were then squeezed together into a space the size of a soccer ball. That compression made everything ferociously hot and energetic.