Particle physics talk engages an open-air audience in new venture for the IOP

28 May 2015

CERN scientist Professor Tara Shears engaged an open-air audience with particle physics in a busy quarter of London’s King’s Cross on 27 May, drawing in passers-by as well as more than 200 participants who were seated to hear her speak.
Listen to the lecture below!

The event was held at the Canalside Steps venue next to the towpath of Regent’s Canal, where it also attracted some listeners in the adjacent square and on an overlooking bridge. It was held to launch a new programme of public lectures by the IOP and the site was chosen as it is near the location in King’s Cross where the Institute is to move to a new home.

Prof. Shears, who is a professor of physics at the University of Liverpool and who works on an experiment at the Large Hadron Collider (LHC) at CERN, said it was an exciting time there as scientists prepared to start a new round of experiments at much higher energies than before. During a two-year shutdown a huge amount of work had gone into improving the electrical system and the array of superconducting magnets, so that the LHC was “almost a new machine”, she said.

“We might see something completely unexpected that forces us to rethink things. We have never looked at the universe in this way before – it’s completely new, it’s an adventure,” she said. The discovery there of the Higgs boson in 2012 was amazing, and some might be wondering why on Earth scientists were still running the experiments, she said. “In a sense finding the Higgs boson was the least of our worries when trying to understand the universe. There’s so much more that we want to understand.”

Outlining the Standard Model of particle physics and describing the weak, electromagnetic and strong forces, she said: “There’s one more force I haven’t mentioned yet, and that’s gravity. It’s responsible for the large-scale structure of the universe but at the level of quarks and leptons it’s very weak – 40 orders of magnitude smaller than the weak force. We only really understand gravity at large distance scales.

Tara Shears

“There’s just one more ingredient that we know about and that’s the Higgs field. It’s a type of energy field and we think the whole universe is bathed in it,” she said, explaining that the Higgs boson was the particle associated with this field. “Although we have found the Higgs boson we don’t actually know what sort of Higgs boson it is – whether it’s the one we should have been finding according to the Standard Model or whether it’s a Higgs boson associated with deeper theories of nature.”

Physicists know that the Standard Model is incomplete and that it cannot accommodate gravity, she said, and there are still many mysteries to be investigated, such as dark energy and dark matter. The experiment that she works on at CERN is concerned with antimatter, she explained. “Antimatter might sound like science fiction, but it’s actually science fact, though it’s very rare,” she said, noting that if a quarter of a gram each of matter and antimatter annihilated each other, it would create an explosion equal to several kilotons of TNT. Physicists believed that about half the universe should consist of antimatter but there seemed to be very little around, she said. “We have realised that we can’t explain this within the Standard Model and in our second round of experiments we want to try to find out more. We hope to find a crack in the theory, or a new theory.”

Observations indicated that only 4% of the universe was accounted for by visible matter, with the rest consisting of dark energy and dark matter. The most popular theory for explaining this was supersymmetry, she said, and this was another problem that scientists at CERN wanted to investigate.

These unanswered questions were “quite a shopping list” for CERN she said, but there were other mysteries. “We don’t understand why there are so many fundamental particles, or how to understand gravity, or whether there are other dimensions – those are the questions that keep us awake at night.”

Following her talk there were a number of questions from the audience, including about the nature of the Big Bang, whether micro black holes might be created at the LHC, and whether anti dark matter existed. Prof. Shears said in theory anti dark matter should exist, and an experiment on the international space station was looking for evidence of it annihilating with dark matter.

She was also asked about the relevance of CERN’s work to everyday life. “I don’t think the Higgs boson has any immediate use for anyone, though maybe in 200 years’ time it will have told us how to get cheap energy or something,” she said. But the technologies developed at CERN had had many spin-offs in areas such as security scanning and healthcare, and its effects in inspiring the next generation of scientists and in enabling a diverse group of people to work together were highly important, she said.

On being asked “what comes after the LHC?” Prof. Shears said it was expected to run until 2030 but that meant we had to start thinking about the next step now. CERN had had an idea to build a 100 km tunnel, and other nations that were interested in a bigger facility included China, which had plenty of spare land and was even considering building a city to support such a structure.

The IOP’s chief executive, Paul Hardaker, had introduced Prof. Shears and summed up at the end by urging the audience to view the IOP’s website to follow developments and find out more about the IOP’s next public lecture in September.

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