Today, 4th of July 2012, has been a very long but exciting day. I was here in Lindau, writing my last blog at one o’clock in the morning, when I received an email from a colleague who warned me of a leak from CERN that appeared in the British newspaper The Telegraph, showing an unauthorized video with the discovery of the Higgs particle at CERN. I went immediately to the website. If what they said was true, the discovery seemed to be one of the most spectacular in recent decades in particle physics. In addition, the statistical significance of the discovery had gone up from the four sigmas that many of us had heard rumors of, to not less than five sigma for each experiment, CMS and ATLAS – that is, with a probability of only two parts per million of being wrong. A few hours later the recording disappeared from the Telegraph website.
After a few hours sleep, at 8.00 am, I connected to the CERN website to follow the webcast of the two seminars that were supposed to announce the discovery of the last piece of the Standard Model of fundamental interactions, the Higgs particle. I could see people were already filling the Main Auditorium at CERN. I went quietly to breakfast, and at 9.00 am I was already glued to the screen, while the Director-General – Rolf Heuer – presented to both CMS and ATLAS spokespersons – Joe Incandela and Fabiola Sagnotti. They looked nervous and tired, but very happy. Heurer began: "Today is a special day … and I’m being diplomatic … Today we will take a look at the search for a certain particle … I forgot the name, but I am sure that the experiments will remind me", which made the whole audience brake into laughter.
The first to present the results was Joe Incandela from CMS. At 9.38 in the morning he finally announced the discovery of a new boson, with mass 125.3 + / – 0.6 GeV, with a statistical significance of 4.9 sigma, and with decay rates that were in agreement with the Standard Model Higgs. Then came Fabiola Sagnotti of ATLAS, with a Higgs mass of 126.5 GeV and statistical significance of 5.0 sigma, compatible with the predictions of the Standard Model. So it seemed that CERN scientists had succeeded at last, after nearly 30 years, to complete the search for one of the most elusive particles, having needed for it the terms of 6 consecutive Director-Generals. This discovery is certainly one of the greatest achievements of particle physics of all time, although there is much to explore, and we still need to clarify whether this is really the Higgs boson, the only fundamental scalar of the Standard Model, and not just the lightest partner a larger sector of electroweak symmetry breaking in a theory beyond the Standard Model.
Minutes later we followed on the screens of the main auditorium of Lindau the press conference at CERN, offered by Heuer, Incandela, Gianotti and Evans, which was broadcasted worldwide via webcast from CERN. It is clear that journalists knew the subject well, and were able to ask very smart and appropriate questions. In the press conference were also present Peter Higgs, François Englert, Gerald Guralnik and Chris Hagen, parents together with Tom Kibble and Robert Brout of the idea of the generation of mass for the W and Z bosons, through their interaction with the Higgs boson. My impression was that this extraordinary discovery at CERN was being followed by the media all over the world and would soon reach the television news, and the general public, so it had to be very carefully orchestrated. The truth is that what we saw at CERN was not only impeccable scientific work, but also a great job at coordination with the media.
I was lucky to find myself in Lindau precisely at the time of the announcement of the discovery of the Higgs since it has allowed me to see firsthand the unanimous reaction of the physics Nobel laureates around here, who all agreed to congratulate the scientists at CERN for a capital discovery. Many were whispering the word Nobel prize, to reward the tremendous effort of a community of more than 5000 people between the two experiments, which had worked together in cooperation and competition – as Rolf Heuer insisted – to achieve the goal, fast and efficiently. In fact, some, like Tini Veltman, were surprised that it had been reached so soon, thanks to the good work and tremendous effort of accelerator physicists and computer scientists of the GRID, which have enabled both CMS and ATLAS experiments to reach the nominal luminosity and analytical tools necessary to find "the needle in the haystack."
We had our own press conference at Lindau, with David Gross, Tini Veltman and Carlo Rubbia answering multiple questions from the media, and soon afterwards we had – nicely scheduled by the organizers of this year’s Lindau meeting – an interesting exchange of information with scientists at CERN: John Ellis from the Theory Division and the spokespersons of CMS, ATLAS and LHCb. This session allowed us to discuss further the physical consequences of the discovery of the Higgs boson, its consequences for supersymmetry, and the future of particle physics. In a couple of years, with the upgrade of the LHC up to 14 TeV, and later on with a possible muon collider working as a Higgs factory, one could explore all the Higgs couplings to Standard Model particles and the details of the electroweak symmetry breaking sector. It is definitely a golden moment for particle physics.
Today it has been a long day indeed, but we can all go to sleep with the assurance that the Higgs particle, or something very similar to the Higgs, has finally been discovered at the European laboratory, successfully completing a very complex and delicate race.