2.16pm: Peter Higgs, gets a tissue and wipes his eye as Rolf-Dieter Heuer, Director General ofCERN says, “I think we have it. Do you agree?” Audience responds with resounding “Yes!” Higgs waves to the audience.
“We are entering the era of Higgs measurements” says Giaonetti. LHC has performed miracles beyond design. The conference closes. This is an epochal day in the world of particle physics and will fundamentally help build on how we understand the universe.
2.13pm: As @ProfBrianCox on Twitter explains, “in very simple language. ATLAS and CMS have independently discovered a new particle mass ~ 126 GeV which behaves like SM Higgs”. There. It exists. Giaonetti reminds the fraternity that the final results are the culmination of over 20 years of hard work by scientists around the globe.
2.05pm: Physicists clap and cheer as Giaonetti announces that the Atlas team has significantly narrowed down the search of the Higgs Boson particle. She says that they made a5 sigma discovery at 126.5 GeV while theStandard Model expectation would be 4.6 sigma, which means that it is compatible with the SM prediction. Is this a discovery? As the applause continues, Giaonetti says that she isn’t done yet.
1.53pm: Giaonetti says that “the value of the Higgs boson seems compatible with the Standard Model prediction within two standard deviations.” She is now talking about the Higgs -> ZZ -> 4 leptons (electrons / muons) search channel. She is emphasising the large increase in precision and efficiency for the search over the last year.
1.35pm: Associated Press notes that Joe Incandela, has not yet confirmed that the new particle that scientists have discovered, is indeed the tiny and elusive Higgs boson, popularly referred to as the “God particle.”
Meanwhile Giaonetti is explaining the procedures and how data stood in 2011. She says that like CMS, the Atlas team also focused mainly on diphoton decay. As @profbriancox on Twitter notes, “It’s entirely appropriate to present in Comic Sans”
1.31pm: Giaonetti says the biggest difficulty in 2012 was the data pile-up. She is talking about how they triggered events in their experiments and is now taking a minute to acknowledge the massive computing efforts that have made all their findings possible.
1.24pm: Fabiola Gianotti from the Atlas team is now presenting. She is going over the conditions under which the experiments were performed. It must be noted that the previously announced summary was for the results of the CMS detector. She is talking about the Atlas results.
1.15pm: Incandela concludes by saying they’ve found a new boson, mass 125.3GeV with 4.9 sigma confidence. The hall bursts into applause. That is amazing work.
1.07pm: Incandela presents what he calls an excess of events at a particular energy window “that’s not consistent with the background.” He announces that the combination of two tests they conducted produced a five sigma result which is enough for a discovery. The hall breaks into applause. However as he mentioned earlier, these are still preliminary results though encouragingly strong.
A combination of events spotted at 7 and 8 TeV are now being discussed. Is there a ‘but’ factor? Do we have the Higgs-Boson or not?
Fun fact: Sheldon explained this one time on Big Bang Theory. He was playing pictionary with Penny and Leonard. Time for the nightly rerun of physics as applied to comedy.
1.03pm: Reuters has posted a flash update saying that scientists at the CERN research centre have discovered a new subatomic particle that could be the elusive Higgs boson, which is believed to be crucial in the formation of the universe.
The report is as follows:
“I can confirm that a particle has been discovered that is consistent with the Higgs boson theory,” said John Womersley, chief executive of the UK’s Science & Technology Facilities Council, at an event in London.
Joe Incandela, spokesman for one of the two teams hunting for the Higgs particle told an audience at CERN near Geneva: “This is a preliminary result, but we think it’s very strong and very solid.”
Meanwhile Incandela is discussing the methods he had used to hone results.
12.55pm: Incandela says he’s close to getting to the results. He is talking of diphoton decay, which is when a Higgs boson decays into two energetic photons. He says, there is a 15% improvement in tracking sensitivity of diphoton decay.
Incandela says that they have managed to get a 4-sigma result around 125 GeV with 95% confidence level.
12.50pm: Incandela is talking about the event classes that were used to try and isolate the Higgs Boson. He said they used four different types of events used to look for Higgs boson decay modes. He is also explaining the cross-checking techniques, used by the scientists.
12.45pm: Incandela says that with a higher pile of events, the processing time/event went up greatly. He praises the “computer guys” for ‘speeding things up’. Energy and data losses, and signal-noise problems are being discussed in some detail.
12.39pm: Incandela who is presenting at Cern is clearly nervous. He is is now explaining the mammoth CMS machine that they used to try and isolate the Higgs Boson particle while splitting atoms. He says, “It still surprises us to some extent”. He says that they looked for 5 modes of decay (out of a total of 8). He is trying to speed up his largely technical presentation.
12.36pm: Scientists in Cern have begun showing their conclusive evidence that the Higgs Boson particle or Gods particle exists. First up is Joe Incandela, the leader of the team using the CMS detector to search for new particles. He’ll be followed by Fabiola Gianotti from the other team using the Atlas detector. He starts off by saying that the evidence they are presenting is preliminary, but strongly encouraging.
The Higgs is the last missing piece of the Standard Model, the theory that describes the basic building blocks of the universe. The other 11 particles predicted by the model have been found and finding the Higgs would validate the model. Ruling it out or finding something more exotic would force a rethink on how the universe is put together.
Scientists believe that in the first billionth of a second after the Big Bang, the universe was a gigantic soup of particles racing around at the speed of light without any mass to speak of. It was through their interaction with the Higgs field that they gained mass and eventually formed the universe.
The search for it only began in earnest in the 1980s, first in Fermilab’s now mothballed Tevatron particle collider near Chicago and later in a similar machine at CERN, but most intensively since 2010 with the start-up of the European centre’s Large Hadron Collider.
WHAT IS THE LARGE HADRON COLLIDER?
The Large Hadron Collider is the world’s biggest and most powerful particle accelerator, a 27-km (17-mile) looped pipe that sits in a tunnel 100 metres underground on the Swiss/French border. It cost 3 billion euros to build.
Two beams of protons are fired in opposite directions around it before smashing into each other to create many millions of particle collisions every second in a recreation of the conditions a fraction of a second after the Big Bang, when the Higgs field is believed to have ‘switched on’.
The vast amount of data produced is examined by banks of computers. Of all the trillions of collisions, very few are just right for revealing the Higgs particle. That makes the hunt for the Higgs slow, and progress incremental.
WHAT IS THE THRESHOLD FOR PROOF?
To claim a discovery, scientists have set themselves a target for certainty that they call “5 sigma”. This means that there is a probability of less than one in a million that their conclusions from the data harvested from the particle accelerator are the result of a statistical fluke.
The two teams hunting for the Higgs at CERN, called Atlas and CMS, now have twice the amount of data that allowed them to claim ‘tantalising glimpses’ of the Higgs at the end of last year and this could push their results beyond that threshold.
Dec 20, 2014