Fifty years of Charm

Science In Action

November 1974 became known as the “November Revolution” in particle physics. Two teams on either side of the US discovered the same particle - the “J/psi” meson. On the "J" team, at the Brookhaven National Laboratory, Sau Lan Wu and colleagues were smashing protons and neutrons together and looking for electrons and positron pairs in the debris. Over at Stanford on the other side of the US, Dr Michael Riordan was in a lab with the "psi" team who, in some ways the other direction, were smashing electrons and positrons together to see what was created. They both, unbeknownst to each other, found a peak around 3.1Gev.

It was shortly after that the full significance was clear. The existence of this particle confirmed a new type of quark, theorised in what we now call the Standard Model, but never before observed - the Charm quark. And with Prof Sau Lan Wu’s team’s subsequent discovery of gluons – the things that hold it all together – a pattern appeared in what had been the chaos of high energy physics and the nature of matter. Sau Lan and Michael (author of "The Hunting of the Quark: A True Story of Modern Physics") tell Roland the story.

Prof Matthew Genge and colleagues at the Natural History Museum in London have found evidence of a bacillus growing on samples of the asteroid Ryugu brought back from space by the Hayabusa 2 mission. Rather than evidence for alien life, as they suggest in a paper this month, the contamination shows how easily terrestrial microorganisms can colonise space rocks, even when subjected to the strictest control precautions.

And Per Ahlberg of Uppsala University and colleagues report in Science how they have taken a load of fossilised faecal matter and mapped out the evolution of dinosaur diets. First came the carnivores… then the vegetarian revolution…

(Photo: Samuel Ting (front) shown with members of his J/psi experimental team. Credit: Brookhaven National Laboratory)

Presenter: Roland Pease Producer: Alex Mansfield