page_title: XENON
section_title: XENON100
hierarchical_section_title: XENON / XENON100
caption_attribution_description: English: Bottom PMT array of the XENON100 detector
context_page_description: The XENON dark matter research project, operated at the Italian Gran Sasso National Laboratory, is a deep underground research facility featuring increasingly ambitious experiments aiming to detect dark matter particles. The experiments aim to detect particles in the form of weakly interacting massive particles by looking for rare interactions via nuclear recoils in a liquid xenon target chamber. The current detector consists of a dual phase time projection chamber.
  The experiment detects scintillation and ionization produced when particles interact in the liquid xenon volume, to search for an excess of nuclear recoil events over known backgrounds. The detection of such a signal would provide the first direct experimental evidence for dark matter candidate particles. The collaboration is currently led by Italian professor of physics Elena Aprile from Columbia University.
context_section_description: The second phase detector, XENON100, contains 165 kg of liquid xenon, with 62 kg in the target region and the remaining xenon in an active veto. The TPC of the detector has a diameter of 30 cm and a height of 30 cm. As WIMP interactions are expected to be extremely rare events, a thorough campaign was launched during the construction and commissioning phase of XENON100 to screen all parts of the detector for radioactivity. The screening was performed using high-purity Germanium detectors. In a few cases mass spectrometry was performed on low mass plastic samples. In doing so the design goal of <10⁻² events/kg/day/keV  was reached, realising the world's lowest background rate dark matter detector.
  The detector was installed at the Gran Sasso National Laboratory in 2008 in the same shield as the XENON10 detector, and has conducted several science runs. In each science run, no dark matter signal was observed above the expected background, leading to the most stringent limit on the spin independent WIMP-nucleon cross section in 2012, with a minimum at 2.0×10⁻⁴⁵ cm² for a 65 GeV/c² WIMP mass. These results constrain interpretations of signals in other experiments as dark matter interactions, and rule out exotic models such as inelastic dark matter, which would resolve this discrepancy. XENON100 has also provided improved limits on the spin dependent WIMP-nucleon cross section. An axion result was published in 2014, setting a new best axion limit.
  XENON100 operated the then-lowest background experiment, for dark matter searches, with a background of 50 mDRU (1 mDRU=10⁻³ events/kg/day/keV).
caption: The bottom PMT array of XENON100 contains 80 PMTs which are spaced as closely as possible in order to maximize light collection efficiency.
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