Speaker
Description
Several possible extensions of the Standard Model predict the existence of
a dark sector that is weakly coupled to the visible one: i.e. the two
sectors couple via the vector portal, where a dark photon with mass in the
MeV to GeV range mixes kinetically with the SM photon. If the dark photon
is the lightest state in the dark sector, it will decay to SM particles,
mainly to leptons and possibly light mesons. Due to its weak interactions
with the SM, it can have a non-negligible lifetime. At the LHC, these dark
photons would typically be produced with large boost resulting in
collimated jet-like structures containing pairs of leptons and/or light
hadrons, the so-called lepton-jets (LJs).
This work is focused on the search for "displaced LJs", which are
produced away from the interaction point and their constituents are limited
to electrons, muons, and pions. The requested topology includes one or two
LJs + leptons/jets/MET. The most recent ATLAS results based on samples
collected at a center of mass energy of 13 TeV will be presented.
Results are interpreted in terms of the Falkowsky-Ruderman-Volansky-Zupan
models where dark photons are generated through the decay of a Higgs boson
to intermediate hidden fermions. The Higgs boson is supposed to be produced
via gluon-fusion and for the first time, results are also presented in
terms of the associated production of a Higgs boson with a W/Z and in the
context of inelastic thermal relic dark matter.
