We show that the weakly interacting massive particle scenario of proton-philic spin-dependent inelastic dark matter (pSIDM) can still provide a viable explanation of the observed DAMA modulation amplitude in compliance with the constraints from other experiments after the release of the DAMA/LIBRA-phase2 data and including the recent bound from COSINE–100, that uses the same $NaI$ target of DAMA. The pSIDM scenario provided a viable explanation of DAMA/LIBRA-phase1 both for a Maxwellian WIMP velocity distribution and in a halo–independent approach. At variance with DAMA/LIBRA-phase1, for which the modulation amplitudes showed an isolated maximum at low energy, the DAMA/LIBRA-phase2 spectrum is compatible to a monotonically decreasing one. Moreover, due to its lower threshold, it is sensitive to WIMP–iodine interactions at low WIMP masses. Due to the combination of these two effects pSIDM can now explain the yearly modulation observed by DAMA/LIBRA only when the WIMP velocity distribution departs from a standard Maxwellian. In this case the WIMP mass $m_{\chi }$ and mass splitting $\delta$ fall in the approximate ranges $\text{7\hspace{0.17em}\hspace{0.17em}}\mathrm{GeV}\lesssim m_{\chi }\lesssim 17\mathrm{GeV}$ and $18\mathrm{keV}\lesssim \delta \lesssim 29\mathrm{keV}$. The recent COSINE–100 bound is naturally evaded in the pSDIM scenario due to its large expected modulation fractions.

• Received 31 October 2018

DOI:https://doi.org/10.1103/PhysRevD.99.023017

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Published by the American Physical Society