A little beyond the standard model

The so-called standard particle model is one of the most successful scientific theory in history, such is the amount of things it explains and the number of times it has been put to the test. In fact, few physical theories have the robustness of the standard model in statistical terms. Since it was proposed forty years ago, it has passed all the tests extensively.

All in all, and as with all models, there are some problems that are not exactly easy to answer. For example, it does not explain why there is more matter than antimatter in the universe, when in principle there is no reason for one to be more abundant than the other.

But to great evils, great remedies. Scientists throughout history have speculated with different possibilities that could solve a problem from the theoretical point of view and then have conducted experiments and observations to verify that this was true. Einstein did it when he developed his general theory of relativity and Pauli did it when he came to the conclusion that there had to be a particle that we know today as a neutrino.

Now, four theoretical physicists, Guillermo Ballesteros, Javier Redondo, Andreas Ringwald and Carlos Tamarit, have developed a new model, which they call SMASH, which minimally extends the standard with spectacular results: it solves five of the problems of the standard model in one stroke?

In SMASH, 6 new particles are added to the 17 existing ones. The new particles are three right-handed heavy neutrinos, a triplet-colored fermion, a particle called ro that gives mass to right-handed neutrinos and which, together with the Higgs boson, is responsible for cosmic inflation, and an axion, which is a candidate particle to be the constituent of dark matter.

With these 6 particles the SMASH does 5 things: it produces the observed material-antimatter imbalance that exists in the universe; creates the mysterious tiny masses of the left-handed neutrinos; it explains the strange symmetry that presents the strong interaction that is what keeps the quarks in the nuclei of the atoms; includes the origin of dark matter; and, as if that were not enough, he explains cosmic inflation.

Will this model go anywhere? Will their authors get the Nobel? Will this be the long-awaited paradigm shift in physics? We do not have to run so much. At the moment there are things that SMASH does not explain, such as the so-called hierarchy problem or the cosmological constant.

But one thing does have a good new model: it makes clear and measurable predictions. For example, SMASH says that the mass of axions has to be between 50 and 200 microelectronvolts. New observations of the cosmic microwave background and the results of the experiments that seek axions can say sooner rather than later whether this new hypothesis is our best model of the universe or must be completely discarded.

Reference:
Guillermo Ballesteros, Javier Redondo, Andreas Ringwald, and Carlos Tamarit (2017) Unifying Inflation with the Axion, Dark Matter, Baryogenesis, and the Seesaw Mechanism Phys. Rev. Lett. doi: 10.1103/PhysRevLett.118.071802