In 2012, a scalar particle has been discovered at the LHC (CERN). As of today, its properties
match those of the Higgs boson of the Standard Model (SM), the current theory of
fundamental interactions. This discovery has crowned 50 years of research, including seminal
work done in Belgium by Brout and Englert. It has also opened a new era for particle
physicists, with more-than-ever pressing mysteries to face, including the absence, despite
predictions and indirect indications, of signs of new physics at the LHC.
The overarching objective of this project, lead by a collaboration of theorists and
experimentalists, is to use the Higgs as a probe of still largely unexplored territories beyond
the SM. First, we aim at more precisely determining the Higgs boson couplings within the SM,
including its self-coupling. We will either discover new interactions, or will constrain the range
of possibilities. Concurrently, we will look for new scalar particles, possible siblings of the
Higgs boson, a challenging and far-reaching task. Second, we will focus on a special feature of
the Higgs boson, that of providing a gateway to a whole new world of hidden particles and
interactions, an exploration which may shed light on the dark matter and neutrino mysteries.
The proposal brings together the young generation of physicists that has contributed to the
discovery of the Higgs and now leads a broad, ambitious and original research project on the
high-energy physics frontier.