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The particle content of the SM

The particle content of the νMSM

The current scientific knowledge of the Universe is based on the Standard Model (SM) of particle physics. The model gives us a fantastically precise description of Nature. There are examples, where the numbers from the theory and experiment coincide up to 10 significant digits! However, the particle physicists are actively searching today for something called "Beyond the Standard Model physics". Why should we, if the SM itself is so good?

The answer is that we today know experimentally that the SM has problems. What are they? There are not many in fact, but all are very important for the description of the Universe. They are:

Laboratory experiments:

• Neutrino oscillations

Cosmological observations:

• Baryon asymmetry of the Universe
• Dark Matter
• Dark Energy
• Inflation

Recently, Planck satellite mission confirmed with improved precision the agreement of the Universe history with the ΛCDM model, which incorporates all the mentioned effects and nothing else.

The Early Universe according to PLANCK

Interesting way to explain these facts uses the paradigm of minimal extension of the Standard Model. It tries to solve all the problems with

• Minimal number of new particles
• Avoiding introduction of new scales in the theory

The nice features of this approach are

• It is simple
• One can, and in fact one should, describe the whole evolution of the universe—there is no other physics that can do something to solve the problems the model may have
• This often leads to very nontrivial constraints on the model, connecting laboratory physics and cosmology