Deducing the nature of dark matter from direct and indirect detection experiments in the absence of collider signatures of new physics

TL;DR

The work tackles how to deduce the particle nature of dark matter when collider signals are absent, by adopting a model-independent, effective-field-theory framework for WIMPs with both fermionic and scalar spins and multiple Lorentz structures. It systematically derives annihilation cross sections, relic densities, and detection signatures (direct and indirect, including solar neutrinos and gamma rays) and maps current constraints and near-future prospects onto the space of couplings and masses. The main contributions include a comprehensive classification of coupling-dependent phenomenology, identification of which interaction forms are still viable, and guidelines for interpreting multi-channel astrophysical data to infer DM properties. Overall, the paper demonstrates that, even without LHC evidence, coordinated direct and indirect detection efforts can meaningfully constrain the DM spin and interaction form, guiding the search for the underlying particle physics.

Abstract

Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated within the context of some specific particle physics model or models (e.g. supersymmetry). Here, we attempt to develop a model-independent approach toward the phenomenology of weakly interacting massive particles in the absence of any discoveries at the Large Hadron Collider. In particular, we consider generic fermionic or scalar dark matter particles with a variety of interaction forms, and calculate the corresponding constraints from and sensitivity of direct and indirect detection experiments. The results may provide some guidance in disentangling information from future direct and indirect detection experiments.

Figures (7)

• Figure 1: The thermal relic density of fermionic dark matter with scalar, pseudoscalar, vector, and axial interactions. In the upper left and upper right frames, results are given for effective couplings to each species of standard model fermion of $G_f \times (1\,{\rm GeV}/m_f) = 10^{-8}$, $10^{-7}$, $10^{-6}$, $10^{-5}$, and $10^{-4}$GeV$^{-2}$. In the remaining four frames, results are shown for $G_f = 10^{-8}$, $10^{-7}$, $10^{-6}$, $10^{-5}$, and $10^{-4}$ GeV$^{-2}$. If resonances, coannihilations, or annihilations to final states other than fermion-antifermion pairs are significant, the relic abundance is expected to be significantly lower than shown here. Also shown as horizontal lines is the range of the cold dark matter density measured by WMAP wmap.
• Figure 2: The spin-independent WIMP-nucleon elastic scattering cross section as a function of WIMP mass for a fermionic WIMP interacting through scalar (left) and vector (right) interactions. Results are given for effective scalar couplings to each quark species of $G_q \times (1\,{\rm GeV}/m_q) = 10^{-8}, 10^{-7}, 10^{-6}, 10^{-5}, {\rm and} \, 10^{-4}$ GeV$^{-2}$ and for effective vector couplings to each quark of $G_q = 10^{-8}, 10^{-7}, 10^{-6}, 10^{-5}, {\rm and} \, 10^{-4}$ GeV$^{-2}$. Also shown as solid curves are the current upper limits from the CDMS cdms and XENON xenon experiments. We do not show the case in which the scalar couplings are equal for each quark species, as its leads to much larger cross sections and are strongly excluded.
• Figure 3: The annihilation rate of WIMPs in the Sun, as a function of the WIMP's mass, for a fermionic WIMP interacting with standard model particles through axial interactions. As before, results are given for effective couplings to each fermion species of $G_q = 10^{-8}, 10^{-7}, 10^{-6}, 10^{-5}, {\rm and} \, 10^{-4}$ GeV$^{-2}$. Also shown as solid lines are the approximate rates needed to be detected by an experiment such as IceCube (20 events per square kilometer, year with a 50 GeV muon energy threshold). The solid lines denote the reach for WIMPs annihilating to bottom quarks (top) or gauge bosons (bottom).
• Figure 4: A summary of the constraints on a fermionic WIMP with scalar, pseudoscalar, vector, and axial interactions, including regions excluded and allowed by direct and indirect detection experiments (note that WIMPs with pseudoscalar and axial interactions are unconstrained by direct detection experiments). If resonances, coannihilations, or annihilations to final states other than fermion-antifermion pairs are significant, smaller couplings than those shown here can lead to the measured relic abundance. See the text for more details.
• Figure 5: The thermal relic density of scalar dark matter with scalar, vector, scalar-psuedoscalar, and vector-axial vector interactions with standard model particles. In the upper left and center right frames, results are given for effective couplings to each species of standard model fermion of $F_f \times (1\,{\rm GeV}/m_f) \times (M_{\psi}/M_{\phi})= 10^{-7}, 10^{-6}, 10^{-5}, {\rm and} \, 10^{-4}$ GeV$^{-2}$. In the other four frames, results for $F_f = 10^{-8}, 10^{-7}, 10^{-6}, 10^{-5}, {\rm and} \, 10^{-4}$ GeV$^{-2}$ are given. If resonances, coannihilations, or annihilations to final states other than fermion-antifermion pairs are significant, the relic abundance is expected to be significantly lower than shown here. Also shown as horizontal lines is the range of the cold dark matter density measured by WMAP wmap.