The Higgs boson, and beyond
With the discovery of the Higgs particle, our understanding of the building blocks of everything we see around us was finally confirmed. But this type of matter is only part of what appears to exist in the universe, and the Higgs boson offers a window to this new world. EU-funded research is helping to pave the way for new breakthroughs.
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The HiggsEFT project is dedicated to study the Higgs boson properties and the potential existence of new particles. It is a theoretical physics project that produces guidance for experiments conducted at CERN’s Large Hadron Collider, says project coordinator Christophe Grojean of German particle accelerator centre DESY, in Hamburg.
Due to end in March 2018, the project has already helped to derive new information about the likely properties of the boson from the data available to date, he reports. It is also looking into ways to maximise the chances of finding evidence of other, as yet undiscovered particles in the collider.
“Learning about possible new physics beyond the standard model is one of the main goals of the project,” Grojean notes. “These are not particles you can observe directly,” he adds. All you can strive to do, he notes, is to find evidence of their interactions with other particles.
EU support for Grojean’s work in HiggsEFT was awarded in the form of a career integration grant from the Marie Skłodowska-Curie Actions programme. This funding, he reports, has helped him to re-establish his career in the EU following several years in Switzerland, at CERN.
What else is out there?
The standard model of particle physics describes what the world is made of and what holds it together. It does so in terms of building blocks that can’t be divided into smaller units: minuscule constituents of matter, diminutive force carriers, and a tiny yet mighty conveyor of mass the Higgs boson.
The confirmation of this short-lived particle’s existence proved that mass is not a property that other particles have to begin with, as had previously been thought, Grojean notes. They acquire it as a result of the interaction with a field that produces Higgs bosons in very specific circumstances, such as the ones created inside the Large Hadron Collider, he explains.
But beyond this insight, many questions about the boson remain to be answered. For example, is there only one kind? Is it really a fundamental particle or is it composed of even smaller building blocks? And where does it get its own mass?
And what does it tell us about other particles that might exist? The standard model, for all its merits, does have gaps. It doesn’t, for example, encompass gravity, one of the four forces that shape our world.
Into the unknown
Nor do the particles of the standard model account for dark matter. This hypothetical substance is thought to be far more abundant in the universe than the stuff we’re used to, but it is undetectable to our senses and has so far remained elusive to our equipment. We can’t see it, for example it doesn’t “shine”, as it doesn’t emit or reflect light. Nor can we touch or feel it, as it goes straight through us.
Our only clue to its existence is the effect of its gravitational pull, which is observable in space. Speculation about its nature is rife.
The quest for new physics could help to produce answers. The particles that compose dark matter may interact with the Higgs boson, says Grojean, and these interactions could help to identify them.
While this is not the only mystery research beyond the standard model could help to solve, a glimpse of just one such particle would be another major milestone. It would extend our understanding of the fabric of the universe into this puzzling hidden world, of which we have only just become aware.