Direct Detection of Dark Matter Electromagnetic Dipole Moments

TL;DR

The paper analyzes direct detection signals from dark matter candidates with electromagnetic dipole moments, realized in gauge-mediated or technicolor-like hidden sectors. It derives non-relativistic cross sections for magnetic and electric dipole interactions, highlighting spin-dependent, spin-independent, and infrared-enhanced contributions and contrasting them with standard constant-contact WIMP scattering. Using data from CDMS, XENON, and DAMA, the authors map allowed regions in the dipole parameter space (g_M, g_E, m_DM) and show that a light DM around 10 GeV with g_M ~ 0.02 or g_E ~ 6e-5 can reconcile DAMA with CDMS/XENON, while heavier masses typically do not. The study demonstrates distinctive experimental signatures across targets and recoil spectra that can differentiate dipole DM from WIMPs and points to targeted future detectors.

Abstract

Dark matter candidates with electromagnetic dipole moments can arise as dark baryons in gauge-mediated or technicolor models. These dark matter candidates interact with nuclei in direct detection experiments mainly through magnetic and/or electric dipole moments. The scattering cross sections depend on the nuclear magnetic moments and nuclear charge and have an infrared enhancement compared with typical WIMP constant contact interactions, leading to distinctive nuclear recoil energy spectra. These characteristics result in an enhanced signal for the DAMA experiment compared with the CDMS or XENON experiments. The positive results of DAMA, along with the null results of CDMS and XENON, are consistent with a dark matter particle with magnetic dipole moment and a mass around ten GeV. Significant direct detection signals can arise from dipolar dark matter with mass up to of order tens of TeV.

Figures (3)

• Figure 1: Fermionic DM contour plots relevant to CDMS (left) and XENON (right). The magnetic dipole moment, the electric dipole moment and the constant contact interaction are shown in the top, middle and bottom plots respectively. The red, yellow, green and blue curves correspond to $0.1$, $1$, $10$ and $100$${\rm event}^{-1}\cdot{\rm kg}\cdot{\rm year}$ respectively. The black crosses correspond to the $90\%$ confidence level limits for the CDMS and XENON data.
• Figure 2: Modulation amplitude $S_m$ in ${\rm event}\cdot{\rm kg}^{-1}\cdot{\rm day}^{-1}\cdot{\rm keVee}^{-1}$ relevant to DAMA for fermionic DM magnetic dipole moment (top left), electric dipole moment (top right) and constant contact interaction (bottom middle). The red, yellow, green and blue curves correspond to fermionic DM masses and gyromagnetic ratios ($m_{\rm DM}$, $g_M$) of ($0.01$ TeV, $0.02$), ($0.1$ TeV, $0.6$), ($1$ TeV, $20$) and ($10$ TeV, $600$) respectively, fermionic DM masses and gyromagnetic ratios ($m_{\rm DM}$, $g_E$) of ($0.01$ TeV, $6\cdot10^{-5}$), ($0.1$ TeV, $2.5\cdot10^{-3}$), ($1$ TeV, $0.1$) and ($10$ TeV, $3$) respectively and fermionic DM masses and total cross section per nucleon ($m_{\rm DM}$, $\sigma_n$) of ($0.01$ TeV, $8\cdot10^{-40}$ cm$^2$), ($0.1$ TeV, $4\cdot10^{-40}$ cm$^2$), ($1$ TeV, $4\cdot10^{-38}$ cm$^2$) and ($10$ TeV, $4\cdot10^{-37}$ cm$^2$) respectively. The black crosses with error bars correspond to the DAMA data consistent with non-vanishing modulation amplitude. The gyromagnetic ratios and the total cross sections per nucleon are chosen such that the modulation amplitudes are of the same order of magnitude than the DAMA data.
• Figure 3: Differential scattering rates as a function of the nuclear recoil energy for $^{23}$Na (left) and $^{73}$Ge (right). The red, green and blue curves correspond to the magnetic dipole moment scattering rate, the electric dipole moment scattering rate and the constant contact interaction scattering rate in ${\rm event}\cdot{\rm kg}^{-1}\cdot{\rm day}^{-1}\cdot{\rm keV}^{-1}$ respectively. The gyromagnetic ratios are chosen to be $g_M=4$ and $g_E=4\cdot10^{-3}$, the total cross section per nucleon is assumed to be $\sigma_n=1\cdot10^{-40}$${\rm cm}^2$ and the fermionic DM mass is assumed to be $m_{\rm DM}=1$ TeV.