Exploring particle physics beyond the Standard Model

The standard model of particle physics (SM) is arguably the best tested theory of physics, providing
an accurate description of virtually all high energy particle physics phenomena observable in
the laboratory. However, the SM also has a number of shortcomings: some of more theoretical
nature such as the fine-tuning problem of the Higgs or the strong-CP problem, and some of more
phenomenological nature such as not allowing for a satisfying implementation of neutrino masses
and the lack of a suitable candidate for the observed dark matter of the Universe.
The SM’s shortcomings have motivated the development of a large number of beyond the SM
(BSM) particle physics models. However, no (conclusive) evidence for any BSM model has been
found to date. The papers included in this thesis study different approaches to search for BSM
In [I], we studied bounds on weakly interacting massive particle (WIMP) DM models arising
from the absence of neutrino signals from DM capture and subsequent DM pair-annihilation in
dense astrophysical objects such as the Sun or the Earth. We interpreted these bounds in a model
independent fashion, focusing in particular on the scaling of the bounds for the case where WIMPs
comprise only a sub-dominant component of the DM.We also used a chemical composition of the
Earth updated with respect to the previous literature, strengthening the bound on spin-dependent
interactions from capture and annihilation in the Earth by approximately a factor 3.
In [II], we studied the collider phenomenology of one particular BSM model, the next-tominimal
supersymmetric standard model (NMSSM). In particular, we focused on 1) the impact
of the presence of the 125 GeV SM-like Higgs boson on the NMSSM parameter space, 2) the
identification of NMSSM specific search channels at the LHC which allow to effectively probe
the NMSSM parameter space allowed by more conventional searches, and 3) an in-depth study of
one of these search channels, the mono-Higgs signature. As shown in [II], this channel allows to
probe the low tanb, large mA regime which is difficult to probe with conventional searches, and
in contrast to many conventional Higgs searches, the reach of the mono-Higgs channel improves
significantly with the increased luminosity expected to be collected at the LHC in current and
future runs.