25 Sep BètaBreak: an update from the Large Hadron Collider
The Large Hadron Collider has been working at almost full power since last April, after a vast renovation. The last time it was running, it gave us the missing piece of the Standard Model: the Higgs boson. But what does this finding mean for our understanding of the world? And what do physicists expect the biggest machine of the world to tell us about the smallest of particles?
Stan Bentvelsen, director of the National Institute of Subatomic Physics (Nikhef), sat down with Erik Verlinde, professor of theoretical physics at the Faculty of Science, during the first BètaBreak this academic year on 16 September to talk about these questions and more.
Before diving into the world of particle physics, it may be helpful to have some background info. CERN is the European Organisation for Nuclear Research, and as the name suggests, this organisation performs research towards elementary particles. They do this by using huge machines with two directed beams of particles in opposite directions. The particles are accelerated using extremely strong magnets, causing individual particles within the beams to collide. The by-products of these impacts provide evidence of the structure of the subatomic world and the laws of nature governing it.
“CERN was founded 61 years ago in Geneva as a response to developments in the USA, but mostly out of theoretical curiosity,” Stan Bentvelsen begins. When asked about the price tag of the research facilities – especially the pricey Large Hadron Collider – Bentvelsen answers: “Everyone (in the world) pays for it. For people in the Netherlands it amounts to (the price of) one cup of coffee every year, which is not too bad.” Fun fact: originally there was talk about the Veluwe in the Netherlands as a location for the research centre.
The Large Hadron Collider
For around two years the collider only worked at half of its power due to troubles with the liquid helium supply. Bentvelsen explains: “The energy of the magnetic field causing the particles to accelerate is similar to as 80 trucks going 100 km/h.” That’s why liquid helium is needed to cool it all down.
The experiments done at the Large Hadron Collider take years of careful preparation, after which the Collider is turned on continuously for 11 months causing enormous amounts of collisions. Around 4 million to be more precise; that’s around 12 thousand collisions a day! And thus huge amounts of data for analysis.
The Standard Model of particles
Erik Verlinde continues: “Theoretical physics was always ahead of the field. Now there are experiments that raise new questions and show whether the theories are also true in nature.” One of those theories is the Standard Model of particle physics. It concerns particle interactions as well as classifies all currently known particles.
Previous experiments by CERN provided evidence in favour of this theory. The most recent and major breakthrough, made using the Large Hadron Collider, was the discovery of the Higgs boson, the last of the particles predicted by the Standard model.
The breakthrough of the Higgs boson
It was already hypothesised that the Higgs particle should exist, as it is needed to explain the mass of particles that are already known. Erik Verlinde seems more focussed on the yet unknown: “I keep myself busy with what comes after the Standard Model. Especially the relation with gravity. There are parts in the galaxy where gravitation is much higher than expected based on the things we know now. Perhaps other particles are needed to explain this.”
Erik Bentvelsen seems to see this as an underappreciation of the discovery of the Higgs boson: “It is certainly not trivial that the particle has been found! It has no charge and spin, making it difficult to detect. You could actually compare it with a fishbowl. We are the fish and what we have detected is the ripple of the water.”
So, what now?
“Well, there are some problems with the Standard Model as it is now,” Bentvelsen clarifies. “It doesn’t really explain why there is so much matter around us and where the antimatter is. Right now we don’t really understand gravity or the energy density in the universe.” Verlinde hypothesises that there might be a second Higgs particle, or other particles. “The theory of Supersymmetry predicts that for every particle there should be an exact counterpart, but these haven’t been found yet.” Bentvelsen adds: “96% of the universe is dark matter and dark energy. So there are so many things we don’t know.”
Inspired by this discussion? Tell us your thoughts about the matter of matter (or perhaps energy) below.
Don’t miss the next BètaBreak on Wednesday 14 October, which is about patenting life! Guests include Michel Haring, Director of Education at the Faculty of Science and head of the Plant Physiology group. Be there at 12 in the main hall. Interested in participating in or organising these events? The BètaBreak committee is looking for new members (announcement in Dutch).