The LUXE experiment and its NPOD extension (new physics searches at optical dump)

I will briefly introduce the LUXE experiment and will focus on the new associated proposal to search for feebly interacting massive particles using the novel NPOD apparatus. The NPOD idea exploits two properties of systems involving collisions between high energy electrons and intense laser pulses. The first property is that the electron-intense-laser collision results in a large flux of hard photons, as the laser behaves effectively as a thick medium. The second property is that the emitted photons free-stream inside the laser and thus for them the laser behaves effectively as a very thin medium. Combining these two features implies that the electron-intense-laser collision is an apparatus, which can efficiently convert UV electrons to a large flux of hard, collinear photons. The photons are directed onto a solid dump in which feebly interacting massive particles may be produced. With the much smaller backgrounds induced by the photon beam compared to those expected in electron- or proton-beam dump experiments and combined with a relatively shorter dump used here, the sensitivity to short lifetimes is unparalleled. I will show that even with a relatively short dump, the search can still be background free. Even with a few days of data taking with a 40 TW laser corresponding to the initial run, LUXE-NPOD will be able to probe an uncharted territory of models with pseudo-scalars and scalars. Furthermore, with a 350TW laser of the main run, LUXE-NPOD will have a unique reach for these models. In particular probe natural of scalar theories for masses above 100 MeV. We note that the new NPOD concept may be ported to other existing or future facilities worldwide, including e.g. future lepton colliders.