Manfred Lindner

We report on a search for sub-GeV dark matter upscattered via the solar reflection mechanism in the heavy mediator scenario. Under the standard halo model, keV–MeV dark matter produces nuclear recoils with energies below the detection threshold of liquid xenon time projection chambers. We enhance sensitivity to low-mass dark matter (DM) by considering dark matter–electron scattering, employing dedicated event selections to reduce the detection threshold and exploiting the additional kinetic energy imparted to the dark matter particle by solar upscattering. Using XENON1T ionization-only and XENONnT low-energy electronic recoil datasets, we exclude previously unconstrained DM-electron scattering cross section for masses between 4.6 and 20 keV / c 2 and between 0.2 and 2 MeV / c 2 , reaching a minimum of 3.41 × 10 − 39 cm 2 for a mass of 0.3 MeV / c 2 at 90% confidence level.

Molecular magnets, although analogous to familiar macroscopic magnets, offer a platform for next generation magnetic storage technologies with far higher data densities and prospective applications in quantum information science. When exposed to an external magnetic field, single molecule magnets enter a metastable configuration that is exceptionally sensitive to low energy excitations. Energy deposited by a dark matter particle can trigger the relaxation of a metastable molecule, releasing Zeeman energy that subsequently propagates through neighboring molecules. This magnetic avalanche encodes the energy deposited in the initial excitation. By combining concepts from chemistry, condensed matter physics, and particle physics, we show that dysprosium and manganese molecules can achieve more than an order of magnitude improvement in sensitivity to dark photon and QCD axion models, respectively, compared with existing detection methods.

We report a 3.3 σ measurement of coherent elastic neutrino-nucleus scattering from solar B 8 neutrinos using a 6.77 t × yr exposure from the XENONnT experiment, inferring a solar B 8 neutrino flux of ( 5 − 2 + 3 ) × 10 6 cm − 2 s − 1 , consistent with previous measurements. In the presence of the B 8 “neutrino fog,” we find no evidence for light dark matter, and observe diminishing returns in sensitivity with increasing exposure. A 93% increase in exposure from the previous search improves the median sensitivity to the nucleon scattering cross section for a 5 GeV / c 2 spin-independent weakly interacting massive particle by 10%. The dataset was also used to measure the weak mixing angle at ∼ 0.02 GeV / c momentum transfer and constrain physics beyond the Standard Model.

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 ± 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 V / cm between 0.3 (0.7) keV NR and 5.0 keV NR . This calibration is crucial for accurately measuring the solar B 8 neutrino coherent elastic neutrino-nucleus scattering and searching for light dark matter particles with masses below 12 GeV / c 2 .

We present a novel realization of Dirac leptogenesis based on the postinflationary reheating phase of the early Universe. An asymmetry generated within the scalar sector via C P -violating and out-of-equilibrium inflaton decays is transferred to chiral neutrinos through Yukawa interactions and then to baryons via electroweak sphalerons. We describe in detail a minimal realization of this mechanism that naturally accommodates small neutrino Yukawa couplings and results in contributions to the effective number of relativistic species, N eff , testable in upcoming cosmological observations.

Coherent elastic neutrino-nucleus scattering ( CE ν NS ) has been experimentally confirmed using neutrinos from pion decay at rest, solar neutrinos, and reactor antineutrinos. Future CE ν NS experiments will lead to precision measurements, which will be a powerful tool to search for new physics beyond the standard model. In this work, we investigate possible deviations from unitarity in the 3 × 3 leptonic mixing matrix that controls the propagation of active neutrinos. Such deviations may originate from the mixing with additional gauge singlet fermions, and depending on their mass scale and mixing, the resulting phenomenology can differ substantially. We explore two well-motivated regimes: the , where the new fermions are heavy and kinematically inaccessible, leading to effective deviations from unitarity in the active sector, and the , where they are light enough to be produced and participate in neutrino propagation and scattering processes. We show how these scenarios modify both CE ν NS and elastic neutrino-electron scattering, and we present the corresponding sensitivity projections for a future CE ν NS reactor experiment obtained by upscaling the CONUS+ experiment, which reported the first observation of reactor CE ν NS . We identify the leading experimental systematics relevant for such an upscaling and demonstrate the resulting capability to probe TeV-scale new physics. Our results highlight the strong potential of CE ν NS to test the structure of the lepton sector and to search for physics beyond the standard model.

We establish comprehensive theoretical benchmarks for weakly interacting massive particles (WIMPs) accessible to ultimate direct detection experiments, focusing on the challenging parameter space between current experimental limits and the irreducible neutrino background. We systematically examine both thermal freeze-out and freeze-in production mechanisms across a range of simplified dark matter models, including s -channel scalar and vector portals, t -channel mediator scenarios, and electroweakly interacting multiplets. For thermal relics, we identify parameter regions where suppressed direct detection cross sections naturally arise through momentum-dependent interactions and blind-spot configurations, while maintaining the correct relic abundance. We extensively investigate freeze-in scenarios, demonstrating how feebly interacting massive particles in portal models can populate experimentally accessible parameter space despite their ultraweak couplings. Additionally, we explore how nonstandard cosmological histories—including early matter domination and fast-expanding Universe scenarios—can dramatically alter the relationship between relic density and detection prospects, opening new avenues for discovery. Our analysis provides a roadmap for next-generation experiments approaching the neutrino floor, highlighting complementary detection strategies and identifying the most promising theoretical targets for ultimate sensitivity dark matter searches. These benchmarks establish the theoretical foundation for the final push toward comprehensive coverage of well-motivated WIMP parameter space.