Wednesday, July 4, 2012

Strong hints of the Higgs - live from CERN

Good morning from the restaurant at CERN where I've been watching the announcement of the results from the CMS and ATLAS experiments at the Large Hadron Collider on the screens. These two experiments have been competing in the hunt for the Higgs boson particle, the missing piece from the standard model jigsaw. The announcement happened simultaneously at CERN, a bit further away on the site from where I was sitting, and at ICHEP in Melbourne (a loooong way from where I was sitting).

As an ex-CERNoise (as they call themselves) I was particularly interested in the announcement. I joined CERN in 2008 to run communications for the Enabling Grids for E-sciencE project, the grid computing infrastructure project that is now the European Grid Infrastructure ( EGI, in collaboration with the World LHC Computing Grid (WLCG) provides the distributing computing infrastructure that has processed the petabytes of data streaming from the four LHC main experiments. It was good to hear a mention of the contribution that computing has made to this momentous global achievement during the talk from Joe Incandela of CMS and Fabiola Gianotti of ATLAS - by reducing the time taken to process the individual events, the results can be announced quicker. No small achievement when the US Tevatron is snapping at their heels

While I was at CERN, the LHC started up in September 2008 to astonishing media and global interest... and then two short weeks later experienced a dramatic quench in one of the magnets deep underground, causing serious damage to the machine and a shut down in running of over a year. The mood at CERN switched from what probably counts as wild excitement in physicist terms (well, we had a staff party, and there was dancing of a sort) to one of pragmatic problem-solving and a collective rolling up of sleeves. The LHC has been a long time in the building, with many many problems to solve along the way  - here was just another phase to plan through. Just over a year later in November 2009, the LHC came back more stable and reliable than before and has since run pretty much flawlessly, ramping up the energy to where it is now at a record breaking 8 TeV.

This morning I was back at CERN for a different meeting but happened to be in residence on site in time for the joint announcement from CMS and ATLAS. I watched the auditorium fill up with students, physicists and a good selection of the world's media. As Peter Higgs arrived to take his seat, a round of gentle applause broke out. After a bit of milling about, a clearly rather nervous Joe Incandela from the CMS experiment took the podium to run through his slides. Following the Twitter feed online, these caused a certain level of bemusement among the Twitterati - the general thrust was I don't really understand this, but it sounds good. Despite working at CERN in the past, I was kind of with them, but the punchline came out pretty clearly at the end of Incandela's talk: We have found a new boson with mass of 125.3  GeV +/- 0.6 at 4.9 standard deviations or "sigma". A loud and extended round of applause in the auditorium followed. To put it in context, one sigma means the results could be random fluctuations in the data, 3 sigma counts as an observation and a 5-sigma result is a discovery. It is about a one-in-3.5 million chance that the signal they see would appear if there were no Higgs particle - so extremely unlikely. However, the CERN press release ( us that the results presented today are preliminary, as the data from 2012 is still under analysis. The complete analysis is expected to be published around the end of July.

Fabiola Gianotti of the ATLAS experiment followed next. "It's tough to talk second," said Fabiola, "because all the clever things have been said." She then went on to very much prove that wasn't the case with a highly technical presentation (despite the comic sans font, which did not go down well online). However, when she got to the part about zooming in on the data... more spontaneous applause starts up (with a slightly ironic echo here in the restaurant). The ATLAS experiment results echo the CMS results - 126.5 GeV for a boson at 5.0 sigma, in agreement with the standard model of physics. In a personal statement, Gianotti said "It is very nice for it to be at this energy because we can measure it here at CERN in abundance – thanks nature!"

Rolf Heuer, the Director General of CERN had a final say. "It's been a global effort, a global success. It has only been possible because of the extraordinary achievements of the experiments, infrastructure and the grid computing." He continued, "We have a discovery, we have a new particle consistent with the Higgs boson. It’s a historic milestone today but we are only at the beginning. We can all be proud and it has global implications for the future. I think we can be very optimistic." Peter Higgs added his congratulations and announced himself "extraordinarily impressed". I suspect he isn't alone.

So a highly significant day for CERN, for the hunt for the Higgs and for me, as its pretty satisfying to be at CERN both for the LHC start up, and the announcement of the strongest hints of the famous particle so far. It's 28 years since the idea of the LHC was first suggested at a physics meeting, more than half my life time ago - I feel very lucky to have been here at this time to see the results of the work of over 20 years, thousands of people worldwide, not to mention six Director Generals. Congratulations!

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