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CERN | Geneva | Switzerland

View Blog | Read Bio

Live blog on CERN Higgs seminar from Melbourne

Don’t forget to refresh the screen periodically to see the new comments

10:57 Now Peter Higgs and François Englert, two of the theorists who predicted this boson, are there at CERN, telling how happy they are. And impressed we finally got it.

10:50 Lots of applause both at CERN and Melbourne, more subdued here though. I guess we feel slightly remote. But I saw many wallabis last night happily hopping in the forest in great anticipation of this event. Even the little pinguins organized a beautiful parade.

10:37 The two main excesses in 2 photon and 4 leptons channels are compatible with each other. The preferred combined value is at 126.5 GeV when all channels are combined, all of them for 2011 data and only the 2 most sensitive ones in 2012. This is also compatible with the strength of the signal a Higgs boson would give at this mass value. The signal also evolved over time nicely varying according to statistics. Nothing could be more convincing. Still we need to convince ourselves that this new boson is exactly what the Standard Model predicts in all aspects. Twice as much data still to come in 2012. Great possibilities still ahead.

10:34 Again, in the 4 lepton channel, nice excess found. So it looks great. A big 5.0 sigma when all is combined. The room breaks into a great applause. Fabiola is visibly both elated and exhausted.

10:24 Moving on to the 4 lepton channel. Again, great improvements in electron identification efficiency and stability, despite the large pile-up (when up to 30 events are all occurring at the same time). So the analysis has improved greatly.

10:11 Ok, she is moving on to the 2 photon channel in 2012. We should expect about 300 events in 2012 data sample if the Higgs has a mass around 126 GeV, according to theory. With an efficiency of about 40%, we find about 170 events, in excess from the background, so slightly more than what the theory predicts. But that’s normal with statistical laws. CMS saw slightly less so on average, we are fine. The excess is estimated at 4.5 sigmas locally (or less if we include the look-elsewhere effect, 2.5 sigma). So seen in 2011 and 2012, doing great.

10:08 With the 2011 data, we were able to find an excess of 2.9 sigma using not only the 2 most sensitive channels (2 photons and 4 leptons) but also with all the other channels. But that was not enough to be convinced.

10:05 Since in 2012 we ran at 8 TeV, we also got more chances of producing Higgs bosons. With the improved analyses, more efficiency in event reconstruction and data taking, we can expect better results too with the 2012 data than 2011.

10:01 She now exlains how much effort was needed to be able to present these results today. Many improvements went into the trigger and also in how fast we reconstructed these events. The GRID played a crucial role in this success.

9:54 It is now Fabiola Gionatti’s turn. She is ATLAS spokesperson. She reviews, like Joe did, the channels that contribute the most at low mass, in the vicinity of 125 GeV where we saw something interesting in last year’s data. The idea is that we want to have two independent samples giving the same results. Then we know something is there. And if she shows that not only CMS, but also ATLAS, sees it, bingo!

9:45 Joe showed many other less important channels, including the tau tau which reduces the overall sensitivity. In total, they have 4.9 sigma at 125.3 GeV when all is combined, fairly all consistent with Standard Model but more checks are in order of course.

9:37 There we go: 5 sigma when both are combined. Welcome to the new boson!

9:32 Now moving to the second most sensitive channel: 4 leptons. Again, new and improved analysis methods promising better results for 2012 data. And again, “a very nice peak” in Joe’s words, a beautiful sigma result 2.5 sigma at 125.5 GeV, so about 125 heavier than a proton.

9:30 At last, here is the 2 photon peak, nice and clear above background. No doubt about it. Gets them an applause. 4 sigma deviation, it’s huge!!! No doubt, we are getting there, slightly stronger even than what is predicted by Standard Model but within error.

9:25 Ok, getting on with the 2 photon canal, the most sensitive one, showing that they used the data directly to calibrate their results, and not only the Monte Carlo simulations. They also used sophisticated methods, (Boosted Decision Trees) to identify their photons. Background and Monte Carlo agree very well. Showing one event that could be from Higgs to 2 photons.

9:20 Joes also is showing that CMS improved their particle identification in 2012. All this to show that we should expect interesting results.

9:15 The LHC was working so well in fact that up to 30 events were piling up at the same time, which made it harder to study the data collected in 2012.

9:10 Showing that the 2012 data is more promising, more chances to produce Higgs at 8 TeV energy than 7 TeV like we did last year. Shows also the the CMS detector was working really well during all the data taking.

9:05 Joe is getting more serious, having gotten good laughs from a very relaxed audience. Everybody is in a good mood. He says he will talk about 5 decay modes but the best 2 are Higgs into 2 photons and Higgs into 4 leptons (leptons are electrons or muons).

9:00 The whole room at CERN quiets down in a flash as Director General Rolf Heuer enters and opens the meeting, greeting the participants in Melbourne. We cheers like school kids. Rolf Heuer, the DG, tells us we will be taking about a particle whose name he forgot… The audience laughs easily at all jokes. Joe Incandela, spokesperson of CMS, will give the first talk.

8:56 François Englert comes in the CERN auditorium under a thunderous applause. He was one of the first to propose the Higgs mecanism with Peter Higgs and Brout.

8:45 Only 15 minutes to go. The auditorium is nearly full. People are waiting with anticipation and the room is crawling with journalists. Everybody seems happy. Someone even has a sign saying: Ciao mamma!

8:30 CERN time – Seminar will start in 30 minutes

Hello everybody,

I am in Melbourne, Australia right now and the seminar is going to be broadcast live here to all participants of the largest physics conference of the year. About 900 jet-lagged physicists are about to be allowed in this auditorium to hear the latest results on the Higgs boson search by CMS and ATLAS.

Remember to refresh your screen periodically and you will be able to see my comments throughout the talk, to help you follow the main points and interpret the results.

Enjoy! Pauline



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