Search for Rich Dark Sectors with the SND@LHC detector and prospects for SND@HL-LHC

Rich dark sectors, i.e. SM-like structures with several particles and interactions below the electroweak scale, can explain neutrino masses, dark matter and the baryon asymmetry. Their signatures, fast semivisible decay chains after scattering in the detector, require dedicated searches. SND@LHC is ideal: high neutrino energies and large boosts probe short decay lengths, i.e. large dark couplings, beyond beam dumps and e+e- colliders. Building on the ongoing Dark Higgs search, the IP1-to-detector simulation chain and DarkNews, we will develop dilepton analyses. SND@HL-LHC will collect over ten times more luminosity, with a magnetized calorimeter and muon filter for muon charge and momentum, and fully electronic silicon tracking for vertices and impact parameters. The Bologna group proposes MAPS pixel planes for better primary and secondary vertexing: during prototyping we will optimize their placement in the target and muon filter for new-physics and SM neutrino studies.