Compatibility of DAMA/LIBRA dark matter detection with other searches in light of new Galactic rotation velocity measurements

TL;DR

The paper reexamines the DAMA/NaI and DAMA/LIBRA annual modulation signal in light of a revised local Galactic velocity, adopting a higher local standard of rest $v_0=250$ km/s within the Standard Halo Model and considering ion channeling effects. Using both spin-independent and spin-dependent WIMP-nucleon couplings, and applying two statistical tests (a likelihood-ratio best-fit analysis and a chi-squared goodness-of-fit test), the authors assess DAMA’s compatibility with null results from CDMS, XENON10, and CRESST I. The updated velocity shifts the DAMA-favored mass ranges to lower values; notably, a small SI region around $m \approx 7$--$8$ GeV persists when channeling is included, while SD-proton-only scenarios allow $m$ in the $5$--$15$ GeV range, albeit with potential tension from Super-K constraints. Overall, the velocity update yields limited improvement in reconciling DAMA with other experiments under the SHM, highlighting the sensitivity of direct-detection interpretations to Galactic dynamics and the need for further data from both direct and indirect searches.

Abstract

The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo, are re-examined in light of new measurements of the local velocity relative to the galactic halo. In the vicinity of the Sun, the velocity of the Galactic disk has been estimated to be 250 km/s rather than 220 km/s. Our analysis is performed both with and without the channeling effect included. The best fit regions to the DAMA data are shown to move to slightly lower WIMP masses. Compatibility of DAMA data with null results from other experiments (CDMS, XENON10, and CRESST I) is investigated given these new velocities. A small region of spin-independent (elastic) scattering for 7-8 GeV WIMP masses remains at 3$σ$. Spin-dependent scattering off of protons is viable for 5-15 GeV WIMP masses for direct detection experiments (but has been argued by others to be further constrained by Super-Kamiokande due to annihilation in the Sun).

Figures (6)

• Figure 1: DAMA best fit parameters (cross section and WIMP mass) for SI only scattering. The DAMA contours are shown at 5$\sigma$, 3$\sigma$, and 90% C.L. (outermost contour is 5$\sigma$). Light/thin lines are for the old value of local standard of rest ($v_0 = 220$ km/s) while the dark/thick lines are the new value ($v_0 = 250$ km/s). The DAMA preferred regions are determined without (Panel A) and with (Panel B) the channeling effect.
• Figure 2: Spin-independent WIMP/nucleon scattering cross section vs. WIMP mass: comparison of DAMA with other null experiments (CRESST I, XENON10, and CDMS) using the goodness-of-fit statistic. Thin/dashed lines are for the old value of local standard of rest ($v_0 = 220$ km/s) while the thick/solid lines are the new value ($v_0 = 250$ km/s). The bound from the total events from DAMA is also shown (red solid line). Panel A does not include the effects of ion channeling while Panel B does take it into account. The DAMA contours are shown at 5$\sigma$, 3$\sigma$, and 90% C.L. (outermost contour is 5$\sigma$). One can see that, with IC included, a sliver of parameter space remains viable at 3$\sigma$ for 7-8 GeV WIMPs.
• Figure 3: Same as Figure \ref{['fig:SIpLR']} but for SD proton-only scattering $(a_n=0)$. Note there are no 3$\sigma$ or 90% C.L. contours at the higher WIMP mass region.
• Figure 4: Same as Figure \ref{['fig:SIpGOF']} but for SD proton-only scattering $(a_n=0)$. Without Super-K included compatiblity is viable for 5-15 GeV WIMP masses for direct detection experiments (but has been argued by others to be further constrained by Super-Kamiokande due to annihilation in the Sun).
• Figure 5: Same as Figure \ref{['fig:SIpLR']} but for SD neutron-only scattering $(a_p=0)$.