Catching UpPostcards from the Energy Frontier by Prof Jon Butterworth
I have been too distracted to write much lately. This is partly due to the demoralising backdrop of UK politics, and partly because I have been having fun with physics and related matters. This is a quick catch up on a few of the good things from that side. I will avoid the politics, not because it isn’t important but because I am sick of it and we all need a break sometimes.
A few weeks ago I went to a workshop organised by Michela Massimi, a philosopher of science in Edinburgh, on “Cross disciplinary perspectives on model-independent searches“. I used to subscribe to Richard Feynman’s view that “philosophy of science is as useful to scientists as ornithology is to birds”, but I have changed my mind. Some of it is much worse, as though an ornithologist were on TV telling everyone birds can’t really fly. But some of it is much better. (Also, I reckon ornithologists do some good for the bird population in some circumstances, even if the birds remain oblivious. But I digress.)
Everyone, even Feynman, has a “philosophy” at some level. Right now, in my field we need to re-examine ours. From the moment I began in particle physics, until 2012, we had a shopping list of questions to answer from the theory, and a well-defined set of ways to address them. To give a few highlights:
- The Standard Model was thought to contain three “generations” of matter (progressively heavier duplicates of the fundamental particles). In 1990 the LEP collider at CERN showed that to be true, by measuring the number of neutrinos.
- The Tevatron collider at Fermilab discovered the top quark in 1995, the final particle in the third generation.
- The flux of neutrinos from the Sun was much smaller than expected. The SuperKamiokande and SNO experiments showed that this was due to the neutrino having a non-zero mass – contrary to the expectation of the Standard Model, and requiring significant new elements to be added to the theory to accommodate it.
- The existence of a quantum field even in the lowest energy state of “empty” space was needed to allow the fundamental particles to have mass; the discovery of the Higgs boson at CERN in 2012 vindicated that prediction.
Done, done, solved, done, and much more. There is more to learn both about neutrinos and the Higgs boson, and there are many open questions remaining, but we are off the map for the first time in decades as far addressing them goes. You can make a shopping list, but it doesn’t tell you which shops to visit. For example, one of the open questions is the nature of Dark Matter. There’s a very extensive review of this here from two of my ATLAS colleagues; as you can see from that, there are many ways to address the question but no guarantees any of them will be definitive.
The Cosmic Shambles Network relies on your support on pledges via Patreon so we can continue to provide great, new, exciting content without the need for third party ads or paywalls.
For as little as $1 a month you can support what we do and get some great rewards for doing so as well. Click the Patreon logo to pledge or find out more.
This situation is exposing some major differences in philosophy amongst physicists, which could turn out to be very important in deciding what to do next. These discussions are happening amongst particle physicists everywhere, ranging from a formal process in Europe through blogs and the media to coffee rooms in practically every lab and university with a physics department.
I think part of the answer is to make our measurements and explorations as model-independent as possible, on the basis that (to borrow a phrase¹) “all models are wrong but some are useful”. This was the topic of Michela’s workshop. In fact much of my recent distraction has been down to a project conceived at a previous meeting she convened, exploiting “Standard Model” measurements to generically probe for new physics, rather than doing dedicated optimised searches for specific models. More here if you are interested.
Other distractions… ATLAS continues to produce lots of results, and here’s one I am especially pleased with because of its model-independent nature. It is also possible to make measurements at the same time as searching, see for example here. All of this is an important part of our voyage, especially when we have no clear map.
Finally, while the LHC is currently closed for renovation, the first ATLAS result from our full “Run 2” data set is out. Many more to come.
¹From statistician George Box, which I first came across in Tamsin Edward’s excellent blog.
Professor Jon Butterworth is a physics professor at University College London and a researcher on the ATLAS experiment at CERN involved with, amongst other things, the discovery of the Higgs Boson. He is the author of two popular science books Smashing Physics and A Map of the Invisible. Postcards From the Energy Frontier is the successor to Jon’s hugely successful blog for The Guardian, Life and Physics. He is @jonmbutterworth on Twitter.