29 September 2014 09:13

CERN, the European Centre for Particle Physics research, celebrates its 60th anniversary today. We're celebrating our 50th anniversary in the same year, and for most of that time physicists at Lancaster University have been working at CERN alongside physicists from around Europe and indeed the world.

Lancaster’s Physics Department was founded in 1967, and Arthur Clegg was a founding group leader working with others from Lancaster at CERN on ‘fixed target’ experiments (where a beam of particles collides with a target in the middle of an experiment, and the debris is analysed) from 1972. David Newton subsequently formed and lead another CERN experiment in 1975. Terry Sloan took this tradition further, becoming the leader of the larger European Muon Collaboration in the 1980s, and revealing unexpected behaviour of quarks when they are inside the atomic nucleus. (Put loosely, they found that while the proton has ‘spin’, like a little quantum mechanical spinning top, that spin is not carried by the quarks that make it up.) This lead to what remains one of Lancaster University’s highest cited papers.

I had the honour of replacing Arthur Clegg on his retirement in 1996 (although not then at the level of Professor!). By that time, Terry Sloan had lead Lancaster into a worldwide collaboration at CERN, the ALEPH experiment that collided electrons and antielectrons in an accelerator called LEP to make very precise measurements of two of the four fundamental forces acting in the universe, the electroweak and the strong interactions. I joined from working as a CERN Fellow on a sister experiment, OPAL and after previously having worked on the scattering of neutrinos and antineutrinos in another CERN experiment, WA21.

Lancaster was already making a big mark at CERN. Alex Finch, along with with Gareth Hughes and Frank Foster, had brought their expertise on the study of the scattering of particles of light off each other (an initially unlikely process, but one that quantum mechanics makes possible), and Alex lead this activity first in ALEPH and later in a working group involving all experiments. Peter Ratoff had joined from yet another of the LEP experiments, called DELPHI, and like myself was active in the group combining the results on the electroweak interaction from all of the experiments. Lancaster was working on one of the most precise measurements available of the strength of the electroweak interaction, and I was able to help complete it, having just made the equivalent measurement in OPAL. Terry Sloan had, in a typically creative manner, also found a way to investigate a predicted but very rare decay process, ‘b to s gamma’, which occurred via an equally exotically named ‘penguin diagram’. Many were astonished that a measurement that for many years set the limits on possible new physics models such as SUSY was even possible, and I was pleased to be able to help bring it to completion (though less pleased at Terry’s keenness on working all through the Christmas and New Year break). In a modest way, I also carried the flag for Lancaster, making one of the most precise measurements of the strength of the strong interaction and leading the group combining the strong interaction measurements from all of the LEP experiments.

It is sometimes shocking to think that even a year before I joined Lancaster, my current experiment at CERN, ATLAS at the Large Hadron Collider, had already formed as a collaboration and was in an advanced state of design. Terry and Peter had been founder members of that collaboration, and established Lancaster as a significant contributor to the building and testing of the innermost part of the experiment, the tracking detector. Both moved on to other things, and I became head of the ATLAS group in 2000. My own contribution was to move Lancaster into a leading position in the study of particles containing beauty quarks (with Maria Smizanska and James Catmore being Lancaster staff having lead the experiment in this area; and the incoming new convenor is another former Lancaster PhD student, Darren Price).

I also took us into the area of software and computing for the experiment. This area has changed hugely since I started working with CERN. In the early days, the volumes of data were small, and so it was often processed and analysed in the Universities. As the experiments became collider experiments, the data volumes grew hugely, and so the bulk of the processing and analysis moved to CERN and its huge computer centre. However, with the LHC, that data volume and rate had become so big that it had to be spread over very many computer centres around the world. I worked on setting-up that world-wide system, and established Lancaster as one of the larger centres. I was charged with fashioning this distributed computing model for ATLAS, and currently chair the collaboration board of project that delivers the worldwide computing for all the experiments, the Worldwide LHC Computing Grid; the project leader, as it happens, is a Lancaster graduate, Ian Bird.

Of course, building experiments has its pleasures, but it is the results that provide much of the excitement. The peak has to have been the search for, investigation and discovery of the Higgs Boson in 2012, in which Lancaster played a major role. More parochially, we also produced the first new particle discovery publication at the end of 2011, which lead to another disrupted Christmas, both for the young PhD student and Research Associates that made it possible and myself. (Note to self: never put out a press release in a slow period for news!) The excitement is not over; Lancaster is in charge of the paper describing the first observation of the decay of the Higgs boson into a ‘matter particle’, in this case the tau lepton; this is a key confirmation that this really is the particle predicted by the theory. While we have not yet seen any other particles that are signatures of ‘new physics’, many models suggest that these take more energy to produce or are produced very rarely. This explains why we are doubling the energy of the LHC when we turn it on again in 2015 and then have a steady programme of increasing the intensity of the beams, making rarer processes more likely to be observed.

What I find so inspiring about working at CERN is the sociology of the place. There are few places where people from countries with traditional (or even active) rivalries come together for a common goal. Indeed, there are sociological and management studies looking at how experiments like ATLAS and ALPEH can even happen. There are few ‘lines-of-command’, but through common interest, enthusiasm and co-operation, highly complex systems not only come together and work, but work well beyond reasonable design expectations. The environment at CERN is immensely stimulating, and the restaurant at the main site the ultimate staff common room. The other great pleasure is seeing the many young minds that make much of the work happen, PhD students and young Research Associates.

CERN has a healthy future ahead of it. The LHC and ATLAS will both continue to be upgraded and to take data for many years. CERN already has plans for even more powerful accelerators, using technologies under research at the Cockcroft Institute and elsewhere, with Lancaster physicists in the ‘interest group’ thinking of the experiments it can host. Those experiments will take place long after I retire, but I have no doubt that CERN and Lancaster will continue to follow the excitement and passion of particle physics long into the future.

What do you think? Share your comments with us below.

Professor Roger Jones teaches on our Physics programmes.


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