Signatures of sub-GeV dark matter beams at neutrino experiments

TL;DR

The paper investigates the possibility that high-luminosity fixed-target neutrino experiments can create and detect a beam of sub-GeV dark matter via light mediators through vector and scalar portals. It develops production mechanisms (direct mediator production and indirect meson decays), establishes viable thermal DM scenarios with careful consideration of relic density and cosmological constraints, and performs a Monte Carlo study to estimate DM fluxes and NC-like scattering signals in near detectors. The results indicate that neutrino facilities could probe DM-nucleon cross sections at the pb level for mχ roughly between 0.1 and 1 GeV, offering a complementary avenue to direct detection and collider searches, though MeV-scale DM remains tightly constrained by cosmology. The work highlights the importance of background discrimination, detector geometry (favoring off-axis detectors in some setups), and timing/directionality in exploiting DM signatures at fixed-target experiments.

Abstract

We study the high-luminosity fixed-target neutrino experiments at MiniBooNE, MINOS and T2K and analyze their sensitivity to light stable states, focusing on MeV--GeV scale dark matter. Thermal relic dark matter scenarios in the sub-GeV mass range require the presence of light mediators, whose coupling to the Standard Model facilitates annihilation in the early universe and allows for the correct thermal relic abundance. The mediators in turn provide a production channel for dark matter at colliders or fixed targets, and as a consequence the neutrino beams generated at fixed targets may contain an additional beam of light dark matter. The signatures of this beam include elastic scattering off electrons or nucleons in the (near-)detector, which closely mimics the neutral current scattering of neutrinos. We determine the event rate at modern fixed target facilities and the ensuing sensitivity to sub-GeV dark matter.

Figures (7)

• Figure 7: Tree-level dark matter scattering off nucleons mediated by the vector and scalar portals.
• Figure 8: Expected number of neutral current-like dark matter nucleon scattering events from V's produced through $\eta$ decays for the ND280 (left) and INGRID (right) detectors at T2K with $m_V=400$ MeV. The regions show greater than 10 (light), 1000 (medium) and $10^6$ (dark) expected events. The dashed curve indicates the value of $\kappa$ required for the dark matter annihilation cross section in the early universe to equal 1 pb.
• Figure 9: Expected number of neutral current-like dark matter nucleon scattering events from V's produced through $\eta$ decays for the MINOS near detector (left) and MiniBooNE (right) with $m_V=400$ MeV. The contours are described in Fig. \ref{['fig:eta1']}.
• Figure 10: Expected number of neutral current-like dark matter nucleon scattering events from direct V production for the ND280 (left) and INGRID (right) detectors at T2K with $m_V=1$ GeV. The contours are described in Fig. \ref{['fig:eta1']}.
• Figure 11: Expected number of neutral current-like dark matter nucleon scattering events from direct V production for the ND280 (left) and INGRID (right) detectors at T2K with $m_V=2$ GeV. The contours are described in Fig. \ref{['fig:eta1']}.