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Scientists Blast Antimatter Atoms With a Laser For The First Time (npr.org)
For the first time, researchers from Indiana University were able to blast antimatter atoms with a laser to measure the light emitted from the anti-atoms. The researchers hope to answer one of the big mysteries of our universe: Why, in the early universe, did antimatter lose out to regular old matter? NPR reports: "The first time I heard about antimatter was on Star Trek, when I was a kid," says Jeffrey Hangst, a physicist at Aarhus University in Denmark. "I was intrigued by what it was and then kind of shocked to learn that it was a real thing in physics." He founded a research group called ALPHA at CERN, Europe's premier particle physics laboratory near Geneva, that is devoted to studying antimatter. That's a tricky thing to do because antimatter isn't like the regular matter you see around you every day. At the subatomic level, antimatter is pretty much the complete opposite -- instead of having a negative charge, for example, its electrons have a positive charge. And whenever antimatter comes into contact with regular matter, they both disappear in a flash of light. In the journal Nature, his team reports that they've now used the special laser to probe this antimatter. So far, what they see is that their anti-hydrogen atoms respond to the laser in the same way that regular hydrogen does. That's what the various theories out there would predict -- still, Hangst says, it's important to check. "We're kind of really overjoyed to finally be able to say we have done this," he says. "For us, it's a really big deal." From the journal Nature: "Researchers at CERN, the European particle physics laboratory outside Geneva, trained an ultraviolet laser on antihydrogen, the antimatter counterpart of hydrogen. They measured the frequency of light needed to jolt a positron -- an antielectron -- from its lowest energy level to the next level up, and found no discrepancy with the corresponding energy transition in ordinary hydrogen."
The reason is that an anti-particle is a particle with opposite charge (both electric and colour) compare to its partner. So an anti-electron has opposite charge to a normal electron, and an anti-quark has opposite colour-charge and electric charge to a normal quark.
A photon does not have any charge, so an anti-photon would have identical properties to a normal photon - they would be identical, and so it makes no sense to talk about them as being different entities.