Recoil Spectra in Xenon for Limit-Frame Dark-Sector Candidates: Rates, Threshold Losses and the Mass at Which the Spectrum Leaves the Window

This study computes nuclear recoil spectra in xenon for dark-sector candidates whose maximum compression is set by a mass-dependent density bound, and compares the resulting rates with published xenon limits. At a reference spin-independent cross section of 1e-46 square centimetres, a 100 GeV candidate gives 53.76 events per tonne-year between 1 and 80 keV, with mean recoil energy 17.1 keV and a fraction 0.79 of events above a 5 keV threshold, whereas a 10 GeV candidate gives 8.54 events per tonne-year with only 0.02 above the same threshold. The density bound on the 100 GeV branch is 1.10e+59 g per cubic centimetre, far above any density a galactic halo particle encounters, so the bound does not change halo rates directly; its role is to exclude candidates whose internal compression in the early universe would have required densities above their own branch. Threshold losses, not total rates, are what separate light candidates from heavy ones in a xenon target. All results are computed from stated assumptions, not measured.