In particle physics, the dark sector is a hypothetical sector of the universe that contains new fundamental particles that only interact with each other and not with known Standard Model particles. The term “dark sector” was first coined in 2006 by Dobrescu and Tait. If the dark sector exists, it could explain some mysteries of astrophysics, such as the nature of dark matter.
The Standard Model (SM) of particle physics explains most observed elementary particles and their interactions. However, there are several aspects of the universe that it does not explain, such as:
the existence of non-baryonic dark matter;
the accelerated expansion of the universe (i.e., dark energy);
the matter–antimatter asymmetry in the universe (i.e., baryogenesis).
It is possible that one or more of these mysteries could be explained by new particles that do not interact with known SM particles. These new particles would comprise a “dark sector”. The name derives from the fact that these hypothetical particles would be difficult to detect experimentally because they would not produce light or other electromagnetic radiation.
There are many candidates for what these hypothetical dark sector particles might be. Some examples include: sterile neutrinos, axions, hidden photons, and gravitons. In addition to being potential candidates for explaining various astronomical observations, some of these dark sector particles have also been proposed as possible candidates for mediating new long-range forces between standard model particles.