Speaker
Description
The light dark matter (LDM) hypothesis provides a compelling framework in which dark matter consists of sub-GeV particles interacting with Standard Model states via a new feebly coupled mediator, such as a dark photon.
The NA64 experiment at CERN’s SPS is specifically designed to probe this scenario through a broad fixed-target program based on missing-energy and missing-momentum techniques.
In its primary electron-beam configuration (NA64-$e$), a 100 GeV electron beam impinges on an active electromagnetic calorimeter acting as a thick target. The experiment searches for events with significant missing energy arising from the production of invisible particles in electron–nucleus interactions. With about $10^{12}$ electrons-on-target (EOT) accumulated during 2016–2022, the absence of signal candidates has allowed NA64 to set some of the most stringent limits in the LDM parameter space. More recently, the program has been extended to positron beams, enhancing sensitivity in the $\sim$100 MeV mass region via resonant $e^+e^-$ annihilation.
A major extension of the program is the muon-beam configuration (NA64-$\mu$), which employs high-energy muons to probe mediators coupled to second-generation leptons. The setup features a high-precision tracking system upstream and downstream of the target, enabling a measurement of the beam missing momentum. A pilot run in 2022, with about $2\times10^{12}$ muons-on-target (MOT), demonstrated the feasibility of this approach.
Finally, the program is complemented by hadron-beam studies (NA64-$h$), aiming to search for hidden-sector particles produced in meson decays and other processes, thereby extending sensitivity to states coupled predominantly to quarks and gluons.
Together, these complementary approaches establish NA64 as a versatile platform for exploring light dark sectors beyond the Standard Model. In this talk, after a brief introduction to the LDM physics case, I will present the NA64 experiment, reviewing the latest results from its four complementary programs and discussing the experiment’s plans for the forthcoming CERN post-LS3 period.
| Parallel session | New Physics Searches: Dark Matter and High-Frequency Gravitational Waves |
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