String Theory: Where Mass Comes From

Together with attempts to find new particles, such as those motivated by string theory, the inability to observe a type of particle called a Higgs boson, are among the major reasons why scientists need advanced particle accelerators for more high-energy experiments.

In the Standard Model of particle physics, particles get their mass through something called the Higgs mechanism. The Higgs mechanism is based on the existence of a Higgs field, which permeates all of space. The Higgs field creates a type of particle called a Higgs boson. For the Higgs field to create a Higgs boson takes a lot of energy, and physicists have so far been unable to create one.

The weak nuclear force falls off very rapidly above short distances. According to quantum field theory, this means that the particles mediating the force — the W and Z bosons — must have a mass (as opposed to the gluons and photons, which are massless).

The problem is that the gauge theories described in the preceding section are mediated only by massless particles. If the gauge bosons have mass, then a gauge theory can’t be sensibly defined. The Higgs mechanism avoids this problem by introducing a new field called the Higgs field.

At high energies, where the gauge theory is defined, the gauge bosons are massless, and the theory works as anticipated. At low energies, the field triggers broken symmetries that allow the particles to have mass.

If the Higgs field does exist, it would create particles known as Higgs bosons. The mass of the Higgs boson isn’t something that the theory tells us, but most physicists anticipate it to be found in the range of 150 GeV. Fortunately, this is within the realm of what we can experimentally search for. Finding the Higgs boson would be the final confirmation of the Standard Model of particle physics.

The Higgs mechanism, Higgs field, and Higgs boson are named after Scottish physicist Peter Higgs. Though he wasn’t the first to propose these concepts, he’s the one they were named after, which is just one of those things that sometimes happens in physics.

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