At Cern, the European laboratory for particle physics, it’s no longer just about the Large Hadron Collider (LHC) and the Higgs boson. Last year’s discovery has left the scientists there a little deflated because the Higgs has turned out to be a boring, just-as-they-predicted kind of particle. The nucleus of the radium atom, on the other hand, is much more interesting.
Early last month, researchers at Cern’s ISOLDE accelerator unveiled a surprising discovery. ISOLDE is fed from the same proton source as the LHC but it smashes its protons into static targets, rather than each other. They were looking at the nucleus of a kind of radium atom that contains 88 protons and 136 neutrons. The agglomeration of these particles, they found, was pear-shaped.
This may seem a little underwhelming at first sight but it may have more significance than the discovery of the Higgs boson. All the Higgs discovery told us was that the theory of nuclear physics known as the “standard model” seems accurate in its estimation of where mass comes from. The pear-shaped nucleus tells us where the standard model might be wrong. If that’s not enough for you, it might also tell us why we are here – why there is something, rather than nothing.
How do you see the shape of an object that is just a hundred-thousand-billionth of a metre in diameter? Throw something at it and listen to the noise it makes. What the researchers at Cern used was another atomic nucleus. The noise comes from the collision energy, which makes the nucleus emit radiation at a frequency that depends on its size and shape. It’s not unlike spinning a selection of coins on their edge on a metal table; as they each settle on to the table, they will make different noises that can be used to tell them apart.
Finding a pear-shaped radium nucleus is not a total surprise. Theories and experiments had already alerted us to the possibility that they exist; there should be some banana-shaped nuclei out there, too. Yet here’s the joy of it all: as researchers find these exotic shapes in their experiments, it allows them to choose between various ideas about the world of subatomic particles. That may be the key to finding out why anything exists at all.
Our best theories tell us that when the universe first came into existence, matter and its nemesis, antimatter, should have been created in equal measure. Because of this, they should have annihilated one another, causing the physical universe to disappear in a puff of liberated energy almost as soon as it was born.
That you are reading this is proof that it didn’t happen and physicists would dearly love to know why. We do have tweaks to the standard model that account for the excess of matter over antimatter and other predictions involve strangely elongated electric fields associated with the positive electric charges held in atomic nuclei. An apple-shaped, perfectly spherical nucleus will not have an elongated field. A grape-shaped nucleus will likely have one, but too small to detect. The warped, extended field of a pear- or banana-shaped nucleus will be much easier to find.
The race is on to find which theories of non-annihilation match with the kinds of stretched fields researchers are just starting to encounter – and thus which theories are candidates for explaining everything that is. See? The Higgs boson was small beer. Exploring the properties of the fruit-shaped nucleus could finally reveal the reason for our existence – or, as they say where ISOLDE sits on the French-Swiss border, our raisin d’être.