Synopsis: Model Tries to Solve Five Physics Problems at Once

A minimal extension to the standard model of particle physics involves six new particles.

The standard model has enjoyed a happy life. Ever since it was proposed four decades ago, it has passed all particle physics tests with flying colors. But it has several sticky problems. For instance, it doesn’t explain why there’s more matter than antimatter in the cosmos. A quartet of theorists from Europe has now taken a stab at solving five of these problems in one go. The solution is a model dubbed SMASH, which extends the standard model in a minimal fashion.

SMASH adds six new particles to the seventeen fundamental particles of the standard model. The particles are three heavy right-handed neutrinos, a color triplet fermion, a particle called rho that both gives mass to the right-handed neutrinos and drives cosmic inflation together with the Higgs boson, and an axion, which is a promising dark matter candidate. With these six particles, SMASH does five things: produces the matter–antimatter imbalance in the Universe; creates the mysterious tiny masses of the known left-handed neutrinos; explains an unusual symmetry of the strong interaction that binds quarks in nuclei; accounts for the origin of dark matter; and explains inflation.

The jury is out on whether the model will fly. For one thing, it doesn’t tackle the so-called hierarchy problem and the cosmological constant problem. On the plus side, it makes clear predictions, which the authors say can be tested with future data from observations of the cosmic microwave background and from experiments searching for axions. One prediction is that axions should have a mass between 50 and 200 𝜇eV. Over to the experimentalists, then.

This research is published in Physical Review Letters.

–Ana Lopes

Ana Lopes is a Senior Editor of Physics.


Features

More Features »

Announcements

More Announcements »

Subject Areas

Particles and FieldsCosmology

Previous Synopsis

Biological Physics

Cell Sensing Improves in a Loose Crowd

Read More »

Next Synopsis

Related Articles

Synopsis: Ion Collisions Reveal Photon-Photon Scattering
Particles and Fields

Synopsis: Ion Collisions Reveal Photon-Photon Scattering

Researchers at the Large Hadron Collider conclusively detect two photons scattering off each other, following initial evidence first published in 2017. Read More »

Viewpoint: Putting Distance Between Collider Events
Particles and Fields

Viewpoint: Putting Distance Between Collider Events

A new way to measure the “distance” between high-energy particle collision events can help researchers interpret events involving, for example, the production of Higgs bosons or of top quarks. Read More »

Viewpoint: Optical Tomography for Supernovae  
Cosmology

Viewpoint: Optical Tomography for Supernovae  

A new optical spectroscopy method can characterize the chemical composition of different layers of the material ejected from type Ia supernovae, delivering clues to the star’s history. Read More »

More Articles