Mirror dark matter and the new DAMA/LIBRA results: A simple explanation for a beautiful experiment
R. Foot
TL;DR
The paper tackles the tension between the DAMA/LIBRA annual modulation signal and null results from other direct-detection experiments. It applies the mirror dark matter framework, featuring a parity-symmetric mirror sector that communicates with ordinary matter through photon-mirror photon kinetic mixing, and computes direct-detection rates using a Rutherford-like cross-section with nuclear form factors and a Maxwellian halo. By re-analyzing DAMA/LIBRA data, incorporating channeling effects in NaI and the 2–6 keVee modulation spectrum, the study finds that a simple H'/He'-dominated halo with a small O' component can explain the observed signal, with a heavier mirror element having mass in the 15–30 GeV range and a mixing parameter $\epsilon$ in the $10^{-9}$ to $10^{-8}$ range; this scenario remains consistent with the null results from CDMS and XENON10. The work also notes that certain hidden sector models can mimic mirror DM behavior, but the mirror framework offers more predictive power, and future low-threshold experiments may provide critical tests of these ideas.
Abstract
Recently, the DAMA/LIBRA experiment has convincingly confirmed the DAMA/NaI annual modulation signal, experimentally demonstrating the existence of non-baryonic dark matter in the halo of our galaxy. Meanwhile, in another part of town, other experiments such as CDMS and XENON10 have not detected any evidence for dark matter. One promising dark matter candidate which can reconcile the positive DAMA annual modulation signal with the null results from the other experiments, is mirror dark matter. We re-analyse the mirror matter interpretation of the DAMA annual modulation signal utilizing a) the new data from DAMA/LIBRA, including the measured energy dependence of the annual modulation signal b) an updated quenching factor which takes into account the channeling effect in $NaI$ crystals and c) the latest constraints from CDMS/Ge, CDMS/Si and XENON10 experiments. We show that the simplest possibility of a $He'$ (and/or $H'$) dominated halo with a small $O'$ component is sufficient to fully explain all of the dark matter experiments. We also point out that a certain class of hidden sector dark matter models, although theoretically less appealing and less constrained, can mimic the success of the mirror dark matter model and hence are also viable.