Long-Range Forces in Direct Dark Matter Searches

TL;DR

The paper explores whether direct dark matter detection signals can be explained by long-range DM–nucleus interactions mediated by a light boson with mass in the $10$–$30$ MeV range. It generalizes the scattering cross section to Yukawa-type interactions, analyzes recoil rates under various halo models, and performs a joint interpretation of DAMA, CoGeNT, and CRESST data using a likelihood framework that accounts for channeling and detector response. The results show that long-range forces can reconcile the positive signals with $m_\chi \sim 8$–$20$ GeV and mediator masses above $\sim 10$ MeV, though bounds from CDMS/XENON and halo-model uncertainties introduce caveats; the analysis also discusses kinetic mixing bounds, DM self-interactions, and implications for dark-photon parameter space. Overall, the study presents long-range interactions as a viable alternative to contact interactions for explaining light-DM signals, highlighting the role of astrophysical priors and particle-physics couplings in shaping the allowed parameter space.

Abstract

We discuss the positive indications of a possible dark matter signal in direct detection experiments in terms of a mechanism of interaction between the dark matter particle and the nuclei occurring via the exchange of a light mediator, resulting in a long-range interaction. We analyze the annual modulation results observed by the DAMA and CoGeNT experiments and the observed excess of events of CRESST. In our analysis, we discuss the relevance of uncertainties related to the velocity distribution of galactic dark matter and to the channeling effect in NaI. We find that a long-range force is a viable mechanism, which can provide full agreement between the reconstructed dark matter properties from the various experimental data sets, especially for masses of the light mediator in the 10-30 MeV range and a light dark matter with a mass around 10 GeV. The relevant bounds on the light mediator mass and scattering cross section are then derived, should the annual modulation effects be due to this class of long-range forces.

Figures (14)

• Figure 1: In the plane $\epsilon$ vs. $m_\phi$, iso--contours of constant rate (chosen as 1 cpd/kg) on a Na target, for a 10 GeV DM particle scattering and for various values for the energy threshold are shown. The galactic halo model is an isothermal sphere with Maxwell--Boltzmann (MB) velocity distribution with velocity dispersion $v_0=220$ km s$^{-1}$ and local density $\rho_0 = 0.3$ GeV cm$^{-3}$.
• Figure 2: Point--like scattering cross sections on proton, as a function of the dark matter mass. The galactic halo has been assumed in the form of an isothermal sphere with velocity dispersion $v_0=220$ km s$^{-1}$ and local density $\rho_0 = 0.3$ GeV cm$^{-3}$. Left panel: The solid green contours A, denote the regions compatible with the DAMA annual modulation effect dama2008dama2010, in absence of channeling. The solid red contours B, refer to the regions compatible with the DAMA annual modulation effect, when the channeling effect is considered at its maximal value. The dotted blue contour refers to the region derived from the CoGeNT annual modulation effect cogentmod, when the bound from the unmodulated CoGeNT data is included. The dashed brown contours denote the regions compatible with the CRESST excess Angloher:2011uu. For all the data sets, the contours refer to regions where the absence of modulation can be excluded with a C.L. of: $7\sigma$ (outer region), $8\sigma$ (inner region) for DAMA, $1\sigma$ for CoGeNT and $3\sigma$ (outer region), $4\sigma$ (inner region) for CRESST. Right panel: The same as in the left panel, with the following difference: the solid orange contour refers to the DAMA annual modulation data, when the fraction of channeling is varied in its allowed interval Bernabei:2007hw. Again, the contour refers to the region where absence of modulation can be excluded with a C.L. $7\sigma,8\sigma$.
• Figure 3: Point--like scattering cross sections on proton, as a function of the dark matter mass. The galactic halo has been assumed in the form of an isothermal sphere with velocity dispersion $v_0=170$ km s$^{-1}$ and local density $\rho_0 = 0.18$ GeV cm$^{-3}$ (left panel); $v_0=270$ km s$^{-1}$ and local density $\rho_0 = 0.45$ GeV cm$^{-3}$ (right panel). Notations are the same as in the left panel of Fig. \ref{['fig:B']}.
• Figure 4: Scattering cross sections on proton, as a function of the dark matter mass, for a long--range mediator of mass $m_\phi = 10$ MeV (left panel) and 30 MeV (right panel). The galactic halo has been assumed in the form of an isothermal sphere with velocity dispersion $v_0=220$ km s$^{-1}$ and local density $\rho_0 = 0.3$ GeV cm$^{-3}$. Notations are the same as in the left panel of Fig. \ref{['fig:B']}.
• Figure 5: The same as in Fig. \ref{['fig:C']}, for an isothermal sphere with velocity dispersion $v_0=170$ km s$^{-1}$ and local density $\rho_0 = 0.18$ GeV cm$^{-3}$.