Axions and relatives across different mass scales

ended

Pseudoscalar QCD axions and axion-like Particles (ALPs) are an excellent candidate for Dark Matter or can act as a mediator particle for Dark Matter. Since the discovery of the Higgs boson, we know that fundamental scalars exist and it is timely to explore the Axion/ALP parameter space more intensively. A look at the allowed axion/ALP parameter space makes it clear that these might exist at low mass (below few eV), as (part of) Dark Matter. Alternatively they might exist at higher mass, above roughly the MeV scale, potentially as a Dark Matter mediator particle. AxScale explores parts of these different mass regions, with complementary techniques but with one research team. Firstly, with RADES, it develops a novel concept for a filter-like cavity for the search of QCD axion Dark matter at a few tens of a micro-eV. Dark Matter Axions can be discovered by their resonant conversion in that cavity embedded in a strong magnetic field. The `classical axion window' has recently received much interest from cosmological model-building and I will implement a novel cavity concept that will allow to explore this Dark Matter parameter region. Secondly, AxScale searches for axions and ALPs using the NA62 detector at CERN's SPS. Especially the mass region above a few MeV can be efficiently searched by the use of a proton fixed-target facility. During nominal data taking NA62 investigates a Kaon beam. NA62 can also run in a mode in which its primary proton beam is fully dumped. With the resulting high interaction rate, the existence of weakly coupled particles can be efficiently probed. Thus, searches for ALPs from Kaon decays as well as from production in dumped protons with NA62 are foreseen in AxScale. More generally, NA62 can look for a plethora of `Dark Sector' particles with recorded and future data. With the AxScale program I aim at maximizing the reach of NA62 for these new physics models.