Two teams of physicists have stumbled across a weird new subatomic particle that's unlike anything else we've ever seen — and it could rewrite the rules of matter as we know them.
Researchers from both the Japanese High Energy Accelerator Research Organisation (KEK) and the Institute of High Energy Physics (IHEP) in China have been studying a particle originally discovered 2005, called Y(4260). As physicists are wont to do, they've been smashing together electrons and positrons to create bucket loads of Y(4260), which exists for just 10-23 seconds before falling apart into different subatomic particles.
But they've observed something weird: a bump in their data, at 3.9 gigaelectronvolts, that corresponds to about four times the weight of a proton. While it's far from certain, that suggests that there exists a new kind of particle — currently known as Z(3900) — which is made of four quarks.
Quarks are the subatomic building blocks that form much of the matter — like neutrons and protons — in our universe. There are six of 'em — called up, down, strange, charm, bottom, and top — but most particles are made up of either two or three of the things, bound together by forces generated by teeny particles called gluons.
Y(4260) is itself thought to be made up of two quarks and an extra gluon, though that's still to be completely confirmed. But in analysing its properties, the teams have seen 460 of these weird new Z(3900) particles that have formed when Y(4260) decays. Their current thinking suggests that the new particle's made up of a charm, anti-charm, up and anti-down quark. That's a total of four — unlike any other particle ever observed.
There are other alternative explanations — it could, for instance, be two two-quark particles interacting so strongly it's impossible to distinguish between them — but it's not known that such a things can ever actually happen. The next step, then, is to keep producing Z(3900) particles and studying them as they decay. If they really are made of four quarks, their behaviour should also be unlike anything we've seen before — and physicists will have to change the way they think about matter for good. [Physical Review Letters via Wired]
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