The COHERENT collaboration searched for scalar dark matter particles produced at the Spallation Neutron Source with masses between 1 and 220 MeV/c 2 using a CsI[Na] scintillation detector sensitive to nuclear recoils above 9 keVnr. No evidence for dark matter is found and we thus place limits on allowed parameter space. With this low-threshold detector, we are sensitive to coherent elastic scattering between dark matter and nuclei. The cross section for this process is orders of magnitude higher than for other processes historically used for accelerator-based direct-detection searches so that our small, 14.6 kg detector significantly improves on past constraints. At peak sensitivity, we reject the flux consistent with the cosmologically observed dark-matter concentration for all coupling constants αD < 0.64, assuming a scalar dark-matter particle. We also calculate the sensitivity of future COHERENT detectors to dark-matter signals which will ambitiously test multiple dark-matter spin scenarios.

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The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory provides an intense, high-quality source of neutrinos from pion decay at rest. This source was recently used for the first measurements of coherent elastic neutrino-nucleus scattering (CEvNS) by the COHERENT collaboration, resulting in new constraints of beyond-thestandard-model physics. The SNS neutrino source will enable further CEvNS measurements, exploration of inelastic neutrino-nucleus interactions of particular relevance for understanding of supernova neutrinos, and searches for accelerator-produced sub-GeV dark matter. Taking advantage of this unique facility, COHERENT's suite of detectors in "Neutrino Alley" at the SNS is accumulating more data to address a broad physics program at the intersection of particle physics, nuclear physics, and astrophysics. This review describes COHERENT's first two CEvNS measurements, their interpretation, and the potential of a future physics program at the SNS.

We present results of several measurements of CsI [Na] scintillation response to 3-60 keV energy nuclear recoils performed by the COHERENT collaboration using tagged neutron elastic scattering experiments and an endpoint technique. Earlier results, used to estimate the coherent elastic neutrino-nucleus scattering (CEvNS) event rate for the first observation of this process achieved by COHERENT at the Spallation Neutron Source (SNS), have been reassessed. We discuss corrections for the identified systematic effects and update the respective uncertainty values. The impact of updated results on future precision tests of CEvNS is estimated. We scrutinize potential systematic effects that could affect each measurement. In particular we confirm the response of the H11934-200 Hamamatsu photomultiplier tube (PMT) used for the measurements presented in this study to be linear in the relevant signal scale region. K : CsI[Na], scintillation, nuclear recoils, quenching factor, coherent elastic neutrinonucleus scattering B H11934-200 PMT response linearity B.1 Scale of the 59.5 keV 𝑒𝑒 signal in CsI[Na] B.2 PMT linearity tests with the CsI[Na] B.3 PMT linearity tests with controlled light sources B.4 Conclusion

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory provides an intense, high-quality source of neutrinos from pion decay at rest. This source was recently used for the first measurements of coherent elastic neutrino–nucleus scattering (CEvNS) by the COHERENT Collaboration, which resulted in new constraints of physics beyond the Standard Model. The SNS neutrino source will enable further CEvNS measurements, exploration of inelastic neutrino–nucleus interactions of particular relevance for understanding supernova neutrinos, and searches for accelerator-produced sub-GeV dark matter. Taking advantage of this unique facility, COHERENT's suite of detectors in Neutrino Alley at the SNS is accumulating more data to address a broad physics program at the intersection of particle physics, nuclear physics, and astrophysics. This review describes COHERENT's first two CEvNS measurements, their interpretation, and the potential of a future physics program at the SNS. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 73 is September 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.