Recent Progress in Search for Dark Sector Signatures

What is it about?

There is a ‘light’ hidden sector (dark sector), present in many models of new physics beyond the Standard Model, which contains a colorful spectrum of new particles. Recently, it has been shown that this spectrum can give rise to unique signatures at colliders when the mass scale in the hidden sector is well below a TeV; as in Hidden Valleys, Stueckelberg extensions, and Unparticle models. These physics models produce unique signatures of collimated leptons at high energies. By studying these ephemeral particles we hope to trace the history of the Universe. Our present theories lead us to believe that there is something new just around the corner, which should be accessible at the energies made available by modern colliders.

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Why is it important?

The models mentioned in this paper address the recent astrophysical observations, showing an anomalous excess of cosmic-ray leptons, by proposing a variety of settings that impact the hidden sector and which give rise to a plethora of new physics signatures both in direct DM experiments and at the LHC. Many recent theories suggest that DM is made up of previously unknown particle(s) on the scale of weak interactions. Specifically, the classes of hidden sector models with low mass DM, which can arise via kinetic mixings, as well as via asymmetric DM models, and dark sectors with new confining gauge groups. A couple of mechanisms for communication between the hidden and visible sectors, aside from by gravity, have been outlined. This communication could be realized via U(1) gauge fields in the hidden sector which mix with the gauge fields in the visible sector via kinetic mixings or via mass mixing by the Stueckelberg mixing mechanism, or via higher dimensional operators. It has been also shown that the recently discovered Higgs boson may act as a link between particles we are familiar with and other particles that have so far avoided detection, such as DM. Searches for new physics that are not tuned on a specific model can remain sensitive to new physics that may not be well described by known theories, and may continue to probe a wide variety of New Physics processes even if some of them are later excluded. Furthermore, the results of such model-independent searches can later be re-interpreted in the context of new models as they are proposed.