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Posted Sep 14, 2018
"That's the next big thing," says Sally Dawson, a theorist at Brookhaven National Laboratory in Upton, NY, and organizer of an event last week at the Fermilab National Laboratory of Accelerators (Fermilab), where more than 100 physicists gathered. Physicists assume that space contains a Higgs field – a bit like an electric field – generated by Higgs bosons hiding in the void. The particles interact with the field to gain energy and, thanks to Albert Einstein's famous equation, E = mc2, the mass.
The Higgs boson, continues Adrian Cho in Science, plays a special role in the standard model, which describes how a dozen types of particles interact through three forces: electromagnetism and weak and strong nuclear forces. (The theory does not include gravity, a major flaw.) The forces in the model come from some mathematical symmetries. But this calculation only works as long as the particles do not start with the mass. So, the mass must emerge in one way or another through the interactions between the massless particles themselves.
For particle physicists eager to explore new boundaries, spotting the Higgs has become a bittersweet triumph. Detected in 2012 on the largest atomic atomizer in the world, the Large Hadron Collider (LHC), this long-sought particle has filled the last gap in the standard model of particles and fundamental forces. But since then, the standard model has withstood all tests, giving no hint to the new physics.
Now, the Higgs itself can offer a way out of the impasse. LHC experimenters at CERN, the European particle physics laboratory near Geneva, Switzerland, are looking for collisions that produce not one but two Higgs boson. Finding more of these rare double-Higgs events than expected could indicate particles or forces exceeding the standard pattern and could even help explain the imbalance of matter and antimatter in the universe.
This Higgs mechanism received resounding support 6 years ago, when experimenters working with the two largest LHC-powered particle detectors, an ATLAS and the compact muon solenoid created an ephemeral particle much like a proton. It breaks down the way the Higgs is supposed to, for example in a pair of photons. But physicists are not sure if they have observed the standard Higgs boson or something subtly different.https: //www.youtube.com/watch? V = S99d9BQmGB0
Double-Higgs events promise a way to say with certainty, revealing how well the Higgs field interacts with itself. An electric field disappears without charge, but the Higgs field must always remain in a vacuum. Otherwise, he could not transmit the mass to the other particles. The standard model assumes that this happens with a Higgs field that interacts with itself and minimizes its energy not by disappearing, but by taking a nonzero force.
Mathematically, there are many ways to design such a schema, and the standard model uses the simplest, single parameter controlled. This parameter, in turn, predicts the rate at which Higgs pairs should emerge in particle collisions, which would allow physicists to test the standard model.
The challenge is to find the extremely rare decays. The standard model predicts that for every 10,000 LHC proton-proton collisions producing a single Higgs boson, about six will produce a pair. These double-higgs events should generate disordered showers of other particles, making them even more difficult to identify. The LHC has probably already produced about 1000 double-Higgs events, but ATLAS and CMS have not yet managed to sift through a signal coming from the background.
However, LHC experimenters are optimistic about their chances, especially because their Higgs boson observation techniques are improving. Last month, they announced that they had detected a particularly messy disintegration mode in which a Higgs spawned a pair of massive particles called bottom quarks, as should be the case in nearly 60% of the decays. This bodes well for double-Higgs searches, as they rely on at least one pair of Higgs that degrades in the most likely way.
LHC experiments may take years to see a signal. Later this year, the LHC will remain inactive for two years for upgrades. In 2026, he will undergo another two-year hiatus to increase his collision rate. The high-brightness LHC would work up to 2034. On paper, only the full cycle will provide enough data to validate the prediction of the standard model. However, some physicists believe they can beat this schedule as their Higgs tracking algorithms continue to improve. "Even before the high-brightness LHC, I think we could get closer to the prediction of the standard model," says Caterina Vernieri, a CMS member at Fermilab.
Of course, all LHC experimenters hope that the double Higgs event rate will exceed the prediction of the standard model. According to Eleni Vryonidou, a theoretician at CERN, this can not be too high or come up against indirect constraints due to observed Higgs decays. However, she estimates that the double Higgs rate could be six times higher than the prediction of the standard model.
Such an improvement would indicate a highly self-interactive Higgs field. It could also point out new ephemeral particles that tend to disintegrate in Higgses, as Higgs' heavier partners predicted by many standard model extensions. And that could have implications far beyond particle physics, says Marcela Carena, a theorist at Fermilab. Physicists do not know why the infant universe has finished with more matter than antimatter. But Carena says that the sudden emergence of a highly self-interacting Higgs field could have blocked the imbalance.
Even if the Double-Higgs event rate does not defy the predictions of standard models, the search for their count will pay off, says Katharine Leney, an ATLAS experimenter at University College London. "What drives a lot of people, including myself, is to be able to say once and for all, by God, that this is not the standard Higgs model."
Image at the top of the page: CERN's particle and microcosm universe offers unique experiences to understand the secrets of matter and to explore the mysteries of the universe. Thanks to Daryl Peebely.
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