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1. Low-energy nuclear recoil calibration of XENONnT with a ${}^{88}\mathrm{Y}\mathrm{Be}$ photoneutron source

   https://doi.org/10.1103/rsl9-j1ky  

   Aprile, E; Aalbers, J; Abe, K; Ahmed_Maouloud, S; Althueser, L; Andrieu, B; Angelino, E; Antón_Martin, D; Arneodo, F; Baudis, L; et al (June 2026, Physical Review D)

   Characterizing low-energy, keV-range nuclear recoils near the detector threshold is one of the major challenges for large direct dark matter detectors. To that end, we have successfully used an Yttrium-Beryllium photoneutron source that emits 152 keV neutrons for the calibration of the light and charge yields of the XENONnT experiment for the first time. After data selection, we accumulated 474 events from 183 hours of exposure with this source. The expected background was $55\pm 12$ accidental coincidence events, estimated using a dedicated 152 hour background calibration run with a Yttrium-PVC gamma-only source and data-driven modeling. From these calibrations, we extracted the light (charge) yield for liquid xenon at our field strength of $23\mathrm{V}/\mathrm{cm}$ between 0.3 (0.7) ${\mathrm{keV}}_{\mathrm{NR}}$ and $5.0{\mathrm{keV}}_{\mathrm{NR}}$ . This calibration is crucial for accurately measuring the solar ${}^8\mathrm{B}$ neutrino coherent elastic neutrino-nucleus scattering and searching for light dark matter particles with masses below $12\mathrm{GeV}/{\mathrm{c}}^2$ . 

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2. MINER reactor based search for axionlike particles using sapphire ( ${\text{Al}}_2{\mathrm{O}}_3$ ) detectors

   https://doi.org/10.1103/tbwx-b5lx  

   Mirzakhani, M; Baker, W; Chaudhuri, M; Dent, J B; Dey, R; Dutta, B; Iyer, V; Jastram, A; Kashyap, V_K S; Kubik, A; et al (August 2025, Physical Review D)

   The absence of definitive results for WIMP dark matter has sparked growing interest in alternative dark matter candidates, such as axions and axionlike particles (ALPs), which also provide insight into the strong CP problem. The Mitchell Institute Neutrino Experiment at Reactor (MINER), conducted at the Nuclear Science Center of Texas A&M University, investigated ALPs near a 1 MW h TRIGA nuclear reactor core, positioned approximately 4 m away. This experiment employed cryogenic sapphire detectors with a low detection threshold ( $\approx 100\mathrm{eV}$ ), equipped with a transition edge sensor capable of detecting athermal phonons. Due to the low-background environment, we were able to exclude ALPs with axion-photon coupling and axion-electron coupling as small as $g_{a\gamma \gamma }={10}^{-5}$ and $g_{aee}={10}^{-7}$ , respectively. Energy depositions below 3 keV were not considered and remain blinded for our coherent elastic neutrino-nucleus scattering analysis. This is the first result demonstrating the MINER experiment’s potential to probe low-mass ALPs, enabled by its low-threshold detector and proximity to a reactor. 

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3. Nucleation efficiency of nuclear recoils in bubble chambers

   https://doi.org/10.1088/1748-0221/17/01/C01030  

   Durnford, D.; Piro, M.-C. (January 2022, Journal of Instrumentation)

   Abstract Bubble chambers using liquid xenon (and liquid argon) have been operated (resp. planned) by the Scintillating Bubble Chamber (SBC) collaboration for GeV-scale dark matter searches and CE ν NS from reactors. This will require a robust calibration program of the nucleation efficiency of low-energy nuclear recoils in these target media. Such a program has been carried out by the PICO collaboration, which aims to directly detect dark matter using C 3 F 8 bubble chambers. Neutron calibration data from mono-energetic neutron beam and Am-Be source has been collected and analyzed, leading to a global fit of a generic nucleation efficiency model for carbon and fluorine recoils, at thermodynamic thresholds of 2.45 and 3.29 keV. Fitting the many-dimensional model to the data (34 free parameters) is a non-trivial computational challenge, addressed with a custom Markov Chain Monte Carlo approach, which will be presented. Parametric MC studies undertaken to validate this methodology are also discussed. This fit paradigm demonstrated for the PICO calibration will be applied to existing and future scintillating bubble chamber calibration data. 

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4. First Indication of Solar ${}^8\mathrm{B}$ Neutrinos via Coherent Elastic Neutrino-Nucleus Scattering with XENONnT

   https://doi.org/10.1103/PhysRevLett.133.191002  

   Aprile, E; Aalbers, J; Abe, K; Ahmed_Maouloud, S; Althueser, L; Andrieu, B; Angelino, E; Antón_Martin, D; Arneodo, F; Baudis, L; et al (November 2024, Physical Review Letters)

   We present the first measurement of nuclear recoils from solar ${}^8\mathrm{B}$ neutrinos via coherent elastic neutrino-nucleus scattering with the XENONnT dark matter experiment. The central detector of XENONnT is a low-background, two-phase time projection chamber with a 5.9 t sensitive liquid xenon target. A blind analysis with an exposure of $3.51\mathrm{t}\times \mathrm{yr}$ resulted in 37 observed events above 0.5 keV, with ( ${26.4}_{-1.3}^{+1.4}$ ) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of $2.73\sigma$ . The measured ${}^8\mathrm{B}$ solar neutrino flux of $\left({4.7}_{-2.3}^{+3.6}\right)\times {10}^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ is consistent with results from the Sudbury Neutrino Observatory. The measured neutrino flux-weighted $\mathrm{CE}\nu \mathrm{NS}$ cross section on Xe of $\left({1.1}_{-0.5}^{+0.8}\right)\times {10}^{-39}{\mathrm{cm}}^2$ is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector. Published by the American Physical Society2024 

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5. Toward alleviating the $H_0$ and $S_8$ tensions with early dark energy-dark matter drag

   https://doi.org/10.1103/PhysRevD.111.023523  

   Simon, Théo; Adi, Tal; Bernal, José Luis; Kovetz, Ely D; Poulin, Vivian; Smith, Tristan L (January 2025, Physical Review D)

   Early dark energy, an additional component of dark energy active in the decade of redshift before recombination, has emerged as one of the most effective models at reducing the Hubble tension between direct measurement of the Hubble parameter, H0, in the late-universe and the ΛCDM prediction when calibrated on Planck. However, it requires a slight increase in the dark matter density, ωcdm, and primordial tilt, ns, that worsens the S8 tension between measurements of weak gravitational lensing at low redshifts and the Planck/ΛCDM prediction. Using a phenomenological fluid model, we investigate whether the inclusion of a drag term between dark matter and early dark energy can compensate for the effect of the increase in power at small-scales, such that both H0 and S8 tensions are simultaneously alleviated. We find that this works if the drag term is dynamically relevant in the post-recombination universe. However, a drag term active before or just around the time at which the early dark energy contribution to the energy density is maximum is significantly constrained due to its impact on the matter perturbations before recombination, and the subsequent modifications to the cosmic microwave background power spectra. 

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