A Forward Multiparticle Spectrometer for the LHC: Hadron spectra and Long-lived particle search

I describe a possible Forward Multiparticle Spectrometer (FMS) that could beinstalled downstream of the superconducting recombination dipole D1 in Run 4,between z = 96 m-126 m to measure multi-TeV hadron spectra in low luminosity ppcollisions at √ s = 14 TeV, as well as p+O and O+O collisions as relevant forcosmic ray showers. Light antinuclei and charmed hadrons at high Feynman x F canbe measured, both of importance for astrophysics. At the full high luminos-ityHL-LHC a search for new long-lived neutral particles (LLPs) decaying in a 20 mlong, 70 cm diameter vacuum pipe to visible decay modes (including γγ, e + e − ,µ + µ − , τ + τ − , c¯ c and jets) can be made. The FMS is especially wellsuited for LLPs with 1 GeV < M (X) < 10 GeV and lifetimes cτ from about 10 m toseveral km. I discuss this as a possible addition to CMS but it has no formalapproval yet, therefore the talk is not given " on behalf of CMS " .