← BACK Research The XENONnT Experiment 2023-11-16 ← Research XENONnT Dark matter direct detection with a dual-phase xenon TPC XENONnT searches for rare particle interactions deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy. It uses liquid xenon to investigate dark matter and low-energy neutrino interactions. Our group works on calibration, detector-response modeling, and simulations: understanding how an energy deposition becomes a measurable signal, and how that understanding supports the interpretation of rare events. Calibration Physics motivation Detector Electronic recoils Nuclear recoils Physics Papers 01 / Our work Calibration at the heart of the measurement Our group contributes to the calibration of XENONnT and to modeling its microscopic response. These efforts connect physical processes in xenon with the signals recorded by the detector. Simulations provide a way to compare a proposed response model with calibration observations. The central questions are concrete: How much light and charge does a low-energy interaction produce? How do fluctuations change the observed signals? How well does the model describe calibration data? Answering these questions is essential for interpreting events near threshold and evaluating the uncertainty in a physics result. Locate the calibration sources Select a source or hover over its label and region to explore where it appears in corrected S1–S2 signal space. ● ²²⁰Rn · ER ● ³⁷Ar · ER ● AmBe · NR ● YBe · low-energy NR Source labels indicate representative calibration regions. The dashed YBe marker identifies the low-signal corner discussed on slide 5 of the supplied talk. Electronic recoils (ER) Radon-220 calibration Upper ER band: larger cS2 at a given cS1. Radon-220 provides low-energy electronic recoils for detector-response studies. Read about this calibration ↓ Reference distribution: S. Li, TAUP2025, slides 3–4; original calibration plot in Phys. Rev. Lett. 131, 041003 (2023). Interactive labels are added for this page. 02 / Physics motivation Evidence for dark matter, a search for its identity Bullet Cluster: lensing mass (blue) and hot gas seen in X-rays (pink). Image credits below. In the Bullet Cluster, the mass inferred from gravitational lensing is displaced from the hot gas. This separation is evidence for dark matter. Its microscopic identity remains unknown. XENONnT searches for rare interactions with xenon to test candidates such as weakly interacting massive particles (WIMPs) and constrain their interaction strength. 03 / Experimental setup An underground observatory for rare interactions Installation overview. E. Aprile et al., Phys. Rev. X 15, 031079 (2025), Fig. 1. XENONnT operates at the Gran Sasso National Laboratory (LNGS), Italy, beneath about 1,400 m of rock. Water shielding, active veto detectors, purified xenon and low-radioactivity materials suppress backgrounds that could mimic rare particle interactions. TPC assembly. Photo: Luigi Di Carlo for the XENON Collaboration. TPC signal formation, drift time and PMT hit patterns. XENON Collaboration / L. Althueser; reproduced in S. Li, TAUP2025, slide 3. How the detector works A particle interaction in liquid xenon produces scintillation light and ionization electrons. Photomultiplier tubes record the prompt light as the S1 signal. An electric field moves the electrons toward the liquid surface, where they are extracted into xenon gas and generate a second light signal, S2. The delay between the two signals and the pattern of S2 light help reconstruct the interaction position. Their sizes provide information about the deposited energy and help distinguish electronic recoils from nuclear recoils. Close to the detection threshold, the production and detection of just a few photons or electrons become central to the measurement. Depth = drift speed × drift time 04 / Calibration measurements From known interactions to detector response Electronic recoil calibration with radon-220 Calibration requires samples of known interactions inside the detector. Radon-220 can be introduced into xenon, where its decay chain produces lead-212 and low-energy electronic recoils. This provides a sample distributed throughout the liquid for studying the electronic recoil response. Shengchao Li coauthored a study characterizing a radon-220 source for XENONnT. The work examined both the useful calibration output and the release of unwanted long-lived radioactive species. It illustrates how source characterization supports calibration in an experiment with stringent background requirements. Read the source-characterization paper. Nuclear recoil calibration with a yttrium–beryllium source Neutron interactions provide a way to study the nuclear recoil response relevant to dark matter and neutrino searches. The XENON Collaboration used an yttrium–beryllium photoneutron source producing 152 keV neutrons to constrain xenon's light and charge yields near threshold. At a drift field of 23 V/cm, the published analysis reports light-yield measurements over 0.3–5.0 keVNR and charge-yield measurements over 0.7–5.0 keVNR. These are the respective calibration ranges. Understanding this response supports searches for light dark matter and measurements of solar boron-8 neutrinos. Read the nuclear recoil calibration paper. Light and charge yields inferred from XENONnT calibration data at 23 V/cm. Shaded regions at the lowest energies mark the limits of calibration sensitivity. Source: XENON Collaboration, arXiv:2412.10451v2, Fig. 7. View source figure ↗ 05 / Physics From detector understanding to physics The XENON Collaboration uses calibrated detector response in searches for dark matter and studies of neutrinos. Recent results include an ionization-only dark matter search with 7.83 tonne-years of exposure, which found no significant excess above the expected background, and a measurement of solar boron-8 neutrinos through coherent elastic neutrino-nucleus scattering. These results make low-energy detector response a shared concern for dark matter and neutrino physics. Calibration links what the detector records to the interactions being tested. Selected papers and further reading Florian Jörg, Shengchao Li, Jochen Schreiner, Hardy Simgen and Rafael F. Lang, Characterization of a ²²⁰Rn source for low-energy electronic recoil calibration of the XENONnT detector, JINST 18, P11009 (2023). Paper XENON Collaboration, Low-energy nuclear recoil calibration of XENONnT with a ⁸⁸YBe photoneutron source, Phys. Rev. D 113, 112017 (2026). Paper XENON Collaboration, Light Dark Matter Search with 7.8 Tonne-Year of Ionization-Only Data in XENONnT, Phys. Rev. Lett. 137, 051003 (2026). Paper XENON Collaboration, Probing the Solar ⁸B Neutrino Fog with XENONnT, Phys. Rev. Lett. 137, 091807 (2026). Paper XENON Collaboration · Member institutions Figure credits Bullet Cluster: X-ray — NASA/CXC/CfA/M. Markevitch et al.; optical — NASA/STScI, Magellan/U. Arizona/D. Clowe et al.; lensing — NASA/STScI, ESO WFI, Magellan/U. Arizona/D. Clowe et al. Installation overview: E. Aprile et al., Phys. Rev. X 15, 031079 (2025), Fig. 1, CC BY 4.0. TPC assembly: Luigi Di Carlo for the XENON Collaboration. Calibration map: XENON Collaboration, First Dark Matter Search with Nuclear Recoils from the XENONnT Experiment, Phys. Rev. Lett. 131, 041003 (2023), doi:10.1103/PhysRevLett.131.041003, CC BY 4.0. Reproduced via the supplied TAUP2025 slides; interactive source labels added. Meet our group · Selected publications · XENON Collaboration · Back to Research
