Chapter 4
Outlook
In the past 50 years it has been assumed that physics beyond the SM interacted through
(at least) some of the same gauge interactions of the SM. The minimal supersymmetric SM and weakly interacting massive dark matter are the two preeminent and
most influential models based on this paradigm.
This program is now running out of some of the initial momentum because of
the lack of the discovery of new particles. In the absence of new states, the many
parameters, for instance, of the minimal supersymmetric SM are working against its
usefulness as a foil for the SM in mapping possible experimental discrepancies.
In more recent times—mostly under the influence of this lack of any real signal of
the breaking up of the SM—a more general scenario has been attracting increasing
interest. Matter beyond the SM is part of a new sector which is dark because it does
not interact through the SM gauge interactions. The dark sector may contain a wealth
of physics with many particles (some of which are dark matter) and interactions.
From our side, in the visible world, we may glimpse this dark sector through a
portal. If it exists, this portal can take various forms depending on the spin of the
mediator. We have reviewed in this primer the vector case in which the portal arises
from the kinetic mixing between the SM electric (or hyper) charge gauge group and
an U (1) gauge symmetry of the dark sector.
The discovery of the dark photon associated to this new Abelian gauge symmetry
is by far more interesting than finding just a new particle because, if found, this new
gauge boson would be the harbinger of a new interaction and of the existence of a
whole new sector of elementary particles.
Past and current experiments have already restricted an important part of the space
of the parameters of the vector portal, both for the massless and the massive dark
photon. Compared to other searches for models beyond the SM, the parameters are
fewer and the signatures more easily interpreted.
We are now on the verge of a new wave of experiments aiming at further closing
the windows left still open in the interaction between ordinary matter and the dark
photon. The long years of searching in vane for physics beyond the SM has thought
us to be very patient and persevering.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Fabbrichesi et al., The Physics of the Dark Photon,
SpringerBriefs in Physics, https://doi.org/10.1007/978-3-030-62519-1_4
69
Outlook
In the past 50 years it has been assumed that physics beyond the SM interacted through
(at least) some of the same gauge interactions of the SM. The minimal supersymmetric SM and weakly interacting massive dark matter are the two preeminent and
most influential models based on this paradigm.
This program is now running out of some of the initial momentum because of
the lack of the discovery of new particles. In the absence of new states, the many
parameters, for instance, of the minimal supersymmetric SM are working against its
usefulness as a foil for the SM in mapping possible experimental discrepancies.
In more recent times—mostly under the influence of this lack of any real signal of
the breaking up of the SM—a more general scenario has been attracting increasing
interest. Matter beyond the SM is part of a new sector which is dark because it does
not interact through the SM gauge interactions. The dark sector may contain a wealth
of physics with many particles (some of which are dark matter) and interactions.
From our side, in the visible world, we may glimpse this dark sector through a
portal. If it exists, this portal can take various forms depending on the spin of the
mediator. We have reviewed in this primer the vector case in which the portal arises
from the kinetic mixing between the SM electric (or hyper) charge gauge group and
an U (1) gauge symmetry of the dark sector.
The discovery of the dark photon associated to this new Abelian gauge symmetry
is by far more interesting than finding just a new particle because, if found, this new
gauge boson would be the harbinger of a new interaction and of the existence of a
whole new sector of elementary particles.
Past and current experiments have already restricted an important part of the space
of the parameters of the vector portal, both for the massless and the massive dark
photon. Compared to other searches for models beyond the SM, the parameters are
fewer and the signatures more easily interpreted.
We are now on the verge of a new wave of experiments aiming at further closing
the windows left still open in the interaction between ordinary matter and the dark
photon. The long years of searching in vane for physics beyond the SM has thought
us to be very patient and persevering.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
M. Fabbrichesi et al., The Physics of the Dark Photon,
SpringerBriefs in Physics, https://doi.org/10.1007/978-3-030-62519-1_4
69