We got a massive turnout on Monday evening for a public lecture I gave on the Large Hadron Collider at Trinity College Dublin. I was invited to give the talk by Astronomy Ireland and it was a great time to give it as there is still plenty of interest in the Collider because of the black hole ‘controversy’, and because last week saw the first offical conference on results from the LHC. Indeed, there has been very little media attention given to the fact that, in the space of a few months, all four detectors at the LHC have been busily rediscovering the elementary particles of the Standard Model that took so many years to first detect, from pions, muons and kaons right up to W and Z bosons.
A lot of physicists might have a problem with the populist title ‘Black holes, the Hadron Collider and the God particle’; however the title was worked out with Astronomy Ireland, an organisation that knows a thing or two about attracting a wide audience! Also, I think controversies such as the black hole controversy are best tackled head on i.e. by describing early on in the talk what a black hole is and why one doesn’t expect to create one at the LHC (in particle physics, one gets only a minute amount of mass from a very large amount of energy since m = E/c2 ). I also touched on micro-black holes and Hawking radiation; overall I had the distinct feeling the audience enjoyed this part of the talk no end!
As for the term ‘God particle’, I happen to be one of the few physicists who likes this name for the Higgs boson. Yes, it was probably originally ‘that goddamn particle’ due to its elusiveness, but I think ‘God particle’ neatly gets across the importance of the particle; after all it is the interaction of the other particles with the Higgs field that is thought to determine their mass, according to the Standard Model.
I divided the talk into three parts; first, an overview of the LHC – how, what, why etc. Then I devoted the central part to a brief history of particle physics, from the discovery of the nucleus to protons and neutrons, from the hypothesis of quarks to the electroweak interaction and the Standard Model. In the third part, I described extensions to the SM such as supersymmetry and Grand Unified Theory and went over our expectations of the LHC experiments, from the possible detection of the Higgs boson to supersymmetric particles, from candidates for dark matter to the search for assymetries in matter/antimatter decay at LHCb.
The LHCb experiment is of particular interest to an Irish audience, as a group at University College Dublin are heavily involved, despite Ireland’s non-membership of CERN.
Finally, I can never resist showing a couple of slides on the basics; not only do experiments at accelerators give us information on the elemental structre of matter and the interaction of the fundamental forces, they also give us supporting evidence for our underlying theories of modern physics, from the observed mass-increase of particles (predicted by special relativity) to the detection of antiparticles (predicted by quantum theory). You can see the full set of slides for the talk here and a video is available here.
All in all, there was a great atmosphere at the talk and I really enjoyed the occasion. There were plenty of questions afterwards, from queries on black holes to the prospect of detecting extra dimensions. I was also asked about a recent study of the cosmic microwave background (CMB) that may cast doubt on the hypothesis of dark matter (based on a revision of measurements of perturbations in the CMB). I haven’t studied this report yet, but I gave the answer that I always give in public fora: let’s see if other groups replicate the findings before pay too much attention. After all, the postulate of dark matter comes not primarily from measurements of the CMB, but from thousands of measurements of the movement of stars, galaxies, galaxy-clusters and halos. That said, it’s certainly an interesting paper…
I really enjoy giving such talks on particle physics, there are so many fascinating subjects to cover; special relativity, quantum theory, quarks, the fundamental interactions, symmetry breaking, antimatter, dark matter etc. Yet while there are quite a few excellent books for the public on cosmology, there are remarkably few on particles physics… might be fun to try to put one together one day.
Apparently, U.S. newspapers are full of stories on the discovery of the God particle at the Tevatron. It seems these stories are based on an unpublished paper (see discussion on Not Even Wrong) – I wouldn’t pay too much attention just yet.