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cruel disappointment to the world of particle physics. Friday, August 5, at the annual conference Physics High Energy held in Chicago (Illinois) until August 10, the spokesman for two key experiences of the European Organization for Nuclear Research (CERN) near Geneva confirmed that they had not seen new particles in their detectors.
This announcement shower the hopes born in the last month at the LHC (Large Hadron Collider) at CERN, the large particle accelerator of the world: the indices of such an event had pointed their noses, triggering the production of over five hundred theoretical proposals for linking these stirrings of a new particle, never seen before. It would be a major discovery, since this particle would be the first out of the Standard Model, the theoretical framework. It would de facto open new horizons beyond the current knowledge. “It was like when you went to Einstein’s theories of gravitation to explore the Universe” says Nathalie Besson, a researcher at the Commission for Atomic Energy and Alternative Energies (CEA ) and member of Atlas, one of two experiments with CMS to track down these particles.
the discovery would have been at least as important as the first observation of gravitational waves on Earth announced in February. In fact, what is happening at CERN is somewhat equivalent of maritime exploration in the fifteenth th century: an adventure in unknown areas. By collide protons in their gigantic accelerator 27km in circumference, at speeds close to that of light, physicists emit crazy amounts of energy, which turns back in potentially new.
this is the evidence of the existence of the Higgs boson was obtained in 2012, which was the last piece of the puzzle expected. Now violations energies are higher by over 60%, and explored areas are blank. But oil sea out of sight or storms or islands on the horizon? This is the question that arises from the recovery experiments in 2015.
A hangover stinker
The first results were inclined to the third hypothesis. The two detectors, Atlas and CMS, were recorded at the same energy, a slight excess photon production from the theory. Exactly what one would have expected if a new big particle, six times heavier than the Higgs boson was created in the collisions then disintegrated into a pair of photons.
Except physics the infinitely small is governed by quantum mechanics and the laws of chance. Hitting particles does not always give the same result and is similar to a roll of the dice. Sometimes the dice can all fall on the six repeatedly (or, in the case of particles, creating an excess of photons) … But before shouting to the cheat (or discovery), we must launch and relaunch to verify that the abnormal is abnormal and not the fact of a joke chance. That is, if the horizon we are dealing with an island, a sign of hope, or rather to a big wave, equivalent to a disappointing mirage. In March, the probability that it is an island was considered too weak to declare victory. A few months later, with much more data, the camp of the triumph of caution: it was a big wave, it is gone …
“It’s a big disappointment” says Adam Falkowski, CNRS researcher at the laboratory of theoretical physics of the University of Orsay (Essonne) and author of the blog Résonaances. “It’s a stinker hangover” adds his colleague Orsay Djouadi Abdelhak, who says he had not slept much in recent months. “It’s like when Iceland beat England at Euro 2016 , dare Yves Sirois (CNRS), who represented France in the CMS experiment. It was unlikely, surprising and exciting, and some are already speculating on the upheaval in the global hierarchy. We were on the alert, we replayed the match, and unfortunately everything is back to normal. The Standard Model has again triumphed. “
blame it on bad luck
history confirms proverb saying that we should not sell the skin of the bear before killing him. Indeed, caution was always in order. “We regularly see such fluctuations in our data. We must take them seriously, but do not uncork the champagne right away, “, says Nathalie Besson. “We do not have to be optimistic or pessimistic. nature and we still full of secrets is observed to break, “ adds Marumi Kado, coordinator of Atlas analyzes
Nevertheless, this mirage was special. pretty neat, he had been seen in the same place by the two experiments, which are independent. Emissions of photon pairs had already been one of the key signatures to identify the Higgs boson. In short, “smelled boson” , remembers Abdelhak Djouadi. “Either it was the biggest discoveries, is the mother of statistical fluctuations. We are finally in the second case! “, he says. “Some consider theorists are too excited by publishing hundreds of articles. But our job is to make models and compare them with data. There, there were data, so it was normal to test our ideas with “ says the researcher. Finally, neither experimental errors or artifacts, but simply out of luck.
Continued exploration
End of story? No, because the accelerator works very well and produces a large amount of data: five times more than in 2015 and, in three months, the LHC has nearly reached its target in 2016. This year, 50% more bosons Higgs were created from the preliminary two years to discover. One hundred results were presented at the conference in Chicago … especially the sea of oil still agitated. The “ripples” to other energy sources have already been identified, with the caution that even now required before taking them to unknown lands.
Physicists also scrutinize every angle the Higgs boson. The find was one thing, understanding is another. Because it really is a single particle of its kind. We must therefore study how it interacts with others or with itself. Debris photon pairs are only indications of its existence. There are dozens more to explore with the hope of finding something wrong, that would be an indication of a presence still hidden and exciting. “I have trouble keeping all the analyzes that are produced! “, said Yves Sirois. As the LHC will certainly work even beyond 2030, the statistics pranks continue and there will always be careful not to take a tidal wave for a continent.
“We are only at beginning of the adventure , said Fabiola Gianotti, Director General of CERN, in a statement. The superb performance of the LHC accelerator, experiments and computer is extremely good news for a detailed and complete exploration (…) and significant progress in our understanding of fundamental physics. “
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