COSINE-100 and DAMA/LIBRA-phase2 in WIMP effective models
  Assuming a standard Maxwellian for the WIMP velocity distribution, we obtain
the bounds from null WIMP search results of 59.5 days of COSINE-100 data on the
DAMA/LIBRA-phase2 modulation effect within the context of the non-relativistic
effective theory of WIMP-nucleus scattering. Here, we systematically assume
that one of the effective operators allowed by Galilean invariance dominates in
the effective Hamiltonian of a spin-1/2 dark matter (DM) particle. We find
that, although DAMA/LIBRA and COSINE-100 use the same sodium-iodide target, the
comparison of the two results still depends on the particle-physics model. This
is mainly due to two reasons: i) the WIMP signal spectral shape; ii) the
expected modulation fractions, when the upper bound on the time-averaged rate
in COSINE-100 is converted into a constraint on the annual modulation component
in DAMA/LIBRA. We find that the latter effect is the dominant one. For several
effective operators the expected modulation fractions are larger than in the
standard spin-independent or spin-dependent interaction cases. As a
consequence, compatibility between the modulation effect observed in DAMA/LIBRA
and the null result from COSINE-100 is still possible for several
non-relativistic operators. At low WIMP masses such relatively high values of
the modulation fractions arise because COSINE-100 is mainly sensitive to
WIMP-sodium scattering events, due to the higher threshold compared to
DAMA/LIBRA. A next COSINE analysis is expected to have a full sensitivity for
the 5$\sigma$ region of DAMA/LIBRA.
