The direct detection of Dark Matter particles with mass below the GeV-scale
is hampered by soft nuclear recoil energies and finite detector thresholds. For
a given maximum relative velocity, the kinematics of elastic Dark Matter
nucleus scattering sets a principal limit on detectability. Here we propose to
bypass the kinematic limitations by considering the inelastic channel of photon
emission in the nuclear recoil. Our proposed method allows to set the first
limits on Dark Matter below 500 MeV in the plane of Dark Matter mass and cross
section with nucleons. In situations where a Dark Matter-electron coupling is
suppressed, Bremsstrahlung may constitute the only path to probe low-mass Dark
Matter awaiting new detector technologies with lowered recoil energy
thresholds.Comment: 6 pages, 4 figures; assumptions for future projections revised,
references added, conclusions unchanged. Journal versio
