The Higgs boson is a neutral spin-zero boson that was hypothesized in 1964 by Peter Higgs.

Its discovery in 2012 was a landmark in the history of physics. It explained something fundamental: how elementary particles that have mass get their masses.

But it also marked something no less fundamental: the beginning of an era of measuring in detail the particle’s properties and finding out what they might reveal about the nature of the Universe.

One such property is the particle’s mass, which at 125 GeV is surprisingly small. Many theories have been put forward to explain this small mass, but none has so far been confirmed with data.

In their new paper, Dr. D’Agnolo and Dr. Teresi propose a theory to explain both the lightness of the Higgs boson and another fundamental physics puzzle.

According to the theory, in its early moments the Universe is a collection of many universes each with a different value of the Higgs mass, and in some of these universes the Higgs boson is light.

In this multiverse model, universes with a heavy Higgs boson collapse in a big crunch in a very short time, whereas universes with a light Higgs boson survive this collapse.

Our present-day Universe would be one of these surviving light-Higgs universes.

What’s more, the model, which includes two new particles in addition to the known particles predicted by the Standard Model, can also explain the puzzling symmetry properties of the strong force, which binds quarks together into protons and neutrons, and protons and neutrons into atomic nuclei.

Although the theory of the strong force, known as quantum chromodynamics, predicts a possible breakdown in strong interactions of a fundamental symmetry called CP symmetry, such a breakdown is not observed in experiments.

One of the new particles in the model can solve this so-called strong CP problem, making strong interactions CP symmetric.

Moreover, the same new particle could also account for the dark matter that is thought to make up most of the matter in the Universe.

The jury is of course out on whether the new model, or any of the many other models that have been proposed to explain the Higgs boson mass or the strong CP problem, will fly.

“Each model comes with perks and limitations,” Dr. Teresi said.

“Our model stands out because it is simple, generic and it solves these two seemingly unrelated puzzles at once.”

“And it predicts distinctive features in data from experiments that aim to search for dark matter or for an electric dipole moment in the neutron and other hadrons.”

Sources

Raffaele Tito D’Agnolo & Daniele Teresi. 2022. Sliding Naturalness: New Solution to the Strong-CP and Electroweak-Hierarchy Problems. Phys. Rev. Lett 128 (2): 021803; doi: 10.1103/PhysRevLett.128.021803

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