Proton-philic spin-dependent inelastic Dark Matter (pSIDM) as a viable explanation of DAMA/LIBRA-phase2

TL;DR

The paper demonstrates that proton-philic spin-dependent inelastic Dark Matter (pSIDM) remains a viable explanation for DAMA/LIBRA-phase2's annual modulation signal, especially when considering non-standard WIMP velocity distributions and recent experimental constraints.

Contribution

It introduces the pSIDM scenario as compatible with DAMA/LIBRA-phase2 data and recent bounds, highlighting the importance of non-Maxwellian velocity distributions.

Findings

pSIDM can explain DAMA/LIBRA-phase2 modulation with non-Maxwellian velocities.

WIMP mass range is approximately 7-17 GeV with a mass splitting of 18-29 keV.

COSINE-100 bounds are evaded due to large modulation fractions in pSIDM.

Abstract

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 7 GeV $\lesssim m_{\chi}\lesssim$ 17 GeV and 18 keV$\lesssim\delta\lesssim$29 keV. The recent COSINE-100 bound is naturally evaded in the pSDIM scenario due to its large expected modulation fractions.