All the signs suggest that the world's most-wanted particle is finally preparing to show its face. An unmasking will open doors to a whole new level in our understanding of the universe ? and allow the origins of matter to be studied in exquisite detail.
Teams from the two main detectors at the Large Hadron Collider are due to announce the latest results in their search for the Higgs boson, the crucial but elusive final piece in the standard model of particle physics, at a hotly anticipated seminar at CERN near Geneva, Switzerland, on 4 July.
But given the volume of data the LHC has now collected, a flurry of tantalising but incomplete leaks and the hype in advance of the seminar, there is every reason to believe this is it ? or very nearly. "Whether the Higgs exists or not, we will know this week," says Carlo Rubbia, a particle physicist and Nobel laureate.
Nabbing the Higgs would conclude half a century of arduous searching, and count among the greatest triumphs for theoretical physics.
Swimming through molasses
"Relief is one of many emotions that people will feel," says theorist and blogger Matt Strassler of Rutgers University in Piscataway, New Jersey. "There will also be a sense of anticipation: now we get to start studying this thing."
The Higgs boson was proposed in 1964 as part of the standard model, which describes how particles and forces behave and interact. The model is one of the most successful in physics. One by one, every particle it predicts has showed itself at one detector or another ? except the Higgs.
That is troubling. According to the standard model, the Higgs boson is the smallest unit of an omnipresent Higgs field, assigned the role of giving other particles mass. Massless particles like photons slip through it as if the field isn't there, while massive ones slog like swimmers through molasses. Without the field, there could be no matter, or so the theory goes.
The rub is that the Higgs particle itself is subject to this mechanism, so physicists can't predict its mass. For the past 15 years, they have tried to produce the particle in various accelerators by smashing different particles together ? the idea is to shake the Higgs field and prompt its bosons to fall out. The boson itself would quickly decay into a shower of other particles: physicists search the debris for telltale shards.
Double data
Last December, the twin Higgs-hunting experiments at the LHC ? CMS and ATLAS ? reported shards suggesting a Higgs with a mass of around 125 gigaelectronvolts, but they were not statistically significant enough to claim a discovery. The convention is to declare victory when the statistical significance of a particle's signal is 5 sigma, meaning the chance of something else producing it is less than one in a million. December's signals were each about 2 sigma.
Since then, the LHC has collected a lot more data. In April it raised the energy at which it smashes protons together from 7 teraelectronvolts to 8 TeV, a world record. As a result, between 5 April and 15 June, the two experiments collected twice as much data as they did in all of 2011, enough in principle to declare the particle found, or just about, says Guido Tonelli, former head of CMS.
If the announcement is a Higgs discovery, scientists may crack open the champagne, but then they will roll up their sleeves. Finding the Higgs would be a momentous achievement ? but the particle is more of a tool than an end in itself.
"Scientists have a dialogue with nature. Nature has finally answered and now we get to ask new questions," says Frank Wilczek, a Nobel prize-winning physicist. "The best part about discovering the Higgs particle is it gives us a chance of studying the Higgs field," adds Strassler. That could lead to explanations for why the fundamental particles have the different masses they do.
Supersymmetric solution
In the simplest possible universe, physicists believe, all particles should have the same mass unless something ? perhaps the Higgs field, perhaps something else ? made it otherwise.
Even weirder, theory says particles should have masses close to that needed to collapse them into black holes ? but they clearly don't. This "hierarchy problem" of how to keep particles light, and distinct from each other, is one of the biggest holes in the standard model, but it's not the only one. The standard model also can't explain dark matter, thought to make up 85 per cent of the universe's matter, and it has nothing at all to say on the subject of gravity. Knowing the Higgs's mass should lead to a theory that includes these entities.
An existing candidate, supersymmetry, could solve all these problems in one go. The theory predicts that each standard model particle has a heavier superpartner to balance it out. The lightest of those unseen particles could be a candidate for dark matter.
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