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Internal pair production could enable direct detection of dark matter

Dark matter (DM) is a type of matter estimated to account for 80% of the universe's total mass, but it cannot be directly detected using conventional experimental techniques. As DM does not emit, reflect or absorb light, most previous dark matter searches were aimed at observing either its weak interactions with ordinary matter using highly sensitive detectors or other signatures linked to its presence or decay.

Researchers at Texas A&M University recently introduced a new approach that could enable the direct detection of this elusive type of matter, leveraging a process known as the DM internal pair production. Their proposed strategy, outlined in a paper in Â鶹ÒùÔºical Review Letters, could open new possibilities for future DM searches focusing on a wide range of candidate particles.

"The particle nature of DM can be revealed when a DM particle scatters off a nucleus and produces a visible recoil signal," the authors told Â鶹ÒùÔº. "However, for light DM, transferring sufficient energy to a heavy nucleus is kinematically challenging, even if the DM is energetic. To overcome this limitation, we developed a framework where additional particles are produced in the final state, allowing the DM's energy to be shared among them, while the nucleus remains largely at rest."

The detection strategy proposed by Bhaskar Dutta, Aparajitha Karthikeyan, Mudit Rai, and Hyunyong Kim is predicted to enhance the detectability of light DM in scattering experiments. These are research efforts aimed at observing interactions between DM and ordinary matter that can leave detectable traces.

"We propose a novel dark matter–nucleus scattering process involving the emission of a muon pair, electron pair, or photons in short-baseline neutrino experiments, e.g., ongoing short-baseline neutrino facilities at Fermilab, upcoming DUNE, etc., where large dark matter fluxes are expected from the proton-target collision but hard to detect," explained the authors.

"These energetic final states provide distinctive signatures to separate dark matter signals from neutrino backgrounds and offer new ways to probe the underlying dark matter models."

The approach for detecting dark matter proposed by Dutta and his colleagues is rooted in theory predicting that energetic dark matter particles can collide with nuclei in dense materials, such as those employed by various large-scale DM experiments. These collisions can result in the exchange of a temporary quantum fluctuation of light, known as a virtual photon, which in turn prompts the formation of a lepton-antilepton pair.

The researchers propose a strategy for extracting energetic and visible signals associated with the formation of these pairs, which has so far proved difficult. This strategy could be employed as part of future DM searches, potentially contributing to its detection and shedding light on its origin and composition.

"So far, we have applied our newly developed mechanism in the context of short-baseline neutrino experiments," added the authors. "Encouraged by these results, we plan to extend this approach to search for dark matter present in the galaxy or produced in astrophysical sources such as blazars.

"In such scenarios, the resulting energetic signals could be detectable in various dark matter direct and indirect detection experiments, as well as in large neutrino detectors such as DUNE, Hyper-Kamiokande, JUNO, IceCube, and KM3NeT."