Beyond the standard model via extended symmetries and dark matter
In this thesis, we discuss ideas of how to go beyond the Standard Model (SM) of
particle physics to incorporate the cosmological observations of dark matter and
matter–antimatter asymmetry, and to address the theoretical problems related
to the scalar sector of the SM.
Although the SM has proven to be an excellent description of the interactions
of elementary particles, there is both experimental and theoretical evidence that
this description cannot be complete. Most notably, the cosmological observations
of dark matter (DM) and the matter–antimatter asymmetry in the universe
cannot be explained within the SM.
We have studied simple singlet extensions of the SM. We found out that these
DM and matter–antimatterasymmetry problems cannot be solved simultaneously
by adding only one real singlet scalar, but already a singlet sector consisting of
the scalar and an additional fermionic DM candidate is sufficient. This study
also lays the ground for more complex extensions. Further, we found out that
already one additional scalar can help stabilising the SM vacuum.
Another hint beyond the SM is the vast hierarchy between the mass of
the Higgs boson and the Planck scale, the natural cutoff of the SM. The
naturalness problem associated with light elementary scalars motivates the study
of a dynamical origin behind the electroweak symmetry breaking. Whereas
an underlying strongly coupled sector can explain the hierarchy between the
electroweak and the Planck scales dynamically, there is no simple way to give
masses for the SM fermions without scalars. An alternative route is to combine
the dynamical electroweak symmetry breaking and elementary scalars responsible
for fermion masses. This is motivated by a possibility of highenergy completion
of this class of models via e.g. supersymmetry or a nontrivial ultraviolet fixed
point for the couplings. We have studied a specific model of this kind in the light
of current data from the LHC run I and found the model viable.
The light SM Higgs boson might also imply a symmetry protecting the mass
of the scalar. We have pursued this idea by extending the global symmetry of the
SM scalar sector to SU(4) and studied the spontaneous breaking of this global
symmetry to Sp(4). We found that with elementary scalars, the SM interactions
breaking this global symmetry naturally prefer the Goldstoneboson nature of
the Higgs boson. Further, there is a remaining pseudoGoldstone boson that
can act as a viable DM candidate producing the observed relic abundance while
escaping the current stringent experimental bounds for DM detection.
...
Publisher
University of JyväskyläISBN
9789513961626ISSN Search the Publication Forum
0075465XContains publications
 Artikkeli I: Alanne, T., Chiara, S. D., & Tuominen, K. (2014). LHC data and aspects of new physics. Journal of High Energy Physics, 2014(1), Article 41. DOI: 10.1007/JHEP01(2014)041
 Artikkeli II: Alanne, T., Tuominen, K., & Vaskonen, V. (2014). Strong phase transition, dark matter and vacuum stability from simple hidden sectors. Nuclear Physics B, 889(December 2014), 692–711. DOI: 10.1016/j.nuclphysb.2014.11.001
 Artikkeli III: Alanne, T., Gertov, H., Sannino, F., & Tuominen, K. (2015). Elementary Goldstone Higgs boson and dark matter. Physical Review D, 91(9), Article 095021. DOI: 10.1103/PhysRevD.91.095021
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