XENON100

XENON100
Name	XENON100
Location	Gran Sasso National Laboratory
Status	Decommissioned
Started	2009
Completed	2016
Field	Particle physics
Participants	XENON Collaboration

XENON100 XENON100 was a direct-detection dark matter experiment located at the Gran Sasso National Laboratory in Italy, designed to search for weakly interacting massive particles (WIMPs) using a dual-phase liquid xenon time projection chamber. The experiment built upon earlier efforts such as XENON10 and informed successor projects including XENON1T and XENONnT, operating within a broader context of searches like LUX-ZEPLIN and PandaX. The collaboration involved institutions from Europe, North America, and Asia, coordinating with facilities such as CERN and agencies including the European Research Council.

Introduction

XENON100 aimed to probe WIMP-nucleon cross sections by measuring nuclear recoils in a low-background environment fashioned around a 161-kilogram liquid xenon target and an active 62-kilogram fiducial mass, situated underground at Laboratori Nazionali del Gran Sasso. The experiment leveraged technologies and concepts proven by predecessors such as ZEPLIN-III and contemporaries like CDMS II, positioning results alongside constraints from IceCube and indirect searches by instruments like Fermi Gamma-ray Space Telescope and AMS-02. The project was funded and coordinated across agencies including the Deutsche Forschungsgemeinschaft, National Science Foundation (United States), and national ministries in participating countries.

Detector Design and Instrumentation

The detector was a dual-phase time projection chamber incorporating liquid xenon and gaseous xenon phases, instrumented with photomultiplier tubes from vendors similar to those used by Super-Kamiokande and Borexino. Photons from prompt scintillation (S1) and delayed electroluminescence (S2) were collected by arrays at top and bottom, enabling three-dimensional event reconstruction analogous to techniques in MEG (experiment) and EXO-200. The cryostat and shielding assembly combined low-radioactivity materials selected with assays at facilities such as SNOLAB and MPIK screening laboratories, while the outer shield included lead and polyethylene similar to designs in GERDA. High-voltage and field-shaping systems mirrored engineering practices from NEXT (experiment) and relied on electronic readout and digitizers comparable to those used in ATLAS subdetector electronics.

Data Acquisition and Analysis Techniques

XENON100's data acquisition employed trigger and digitization chains adapted from precision experiments like LHCb and BaBar, recording S1 and S2 waveforms for offline reconstruction. Position reconstruction algorithms used drift-time measurements correlated with top-array hit patterns, borrowing methodologies from T2K and DUNE simulation toolkits. Pulse-shape discrimination and likelihood-based event classification incorporated statistical frameworks used by Planck and LIGO Scientific Collaboration, implementing cuts to separate nuclear recoil candidates from electronic recoils, leveraging calibrations and Monte Carlo simulations generated with toolchains analogous to GEANT4 and FLUKA. Systematic uncertainties were evaluated in the manner of cosmology analyses from WMAP and particle searches like CMS by blind-analysis protocols and cross-validation with simulated datasets.

Calibration and Background Mitigation

Calibration campaigns used internal and external sources including neutron generators and gamma sources akin to those used by DAMA/LIBRA and SNO+ to characterize nuclear recoil responses and electron-recoil bands. Krypton-85 and radon backgrounds were mitigated through cryogenic distillation systems comparable to technology developed for PANDA-X and XMASS, and careful material selection minimized contributions from uranium and thorium chains measured with low-background counters at LNGS facilities. Active veto and fiducialization strategies mirrored approaches from KamLAND and XENON1T, while cosmogenic activation considerations drew on studies from Gran Sasso National Laboratory collaborators and work on CUORE.

Scientific Results and Limits on Dark Matter

XENON100 produced world-leading upper limits on spin-independent WIMP-nucleon cross sections in its operational period, improving constraints across the parameter space explored by CoGeNT, DAMA/LIBRA, and CRESST and informing theoretical models discussed at venues like ICHEP and Rencontres de Moriond. The experiment reported no statistically significant excess consistent with WIMP interactions, setting exclusion curves that guided interpretations in frameworks such as supersymmetric neutralino models studied by groups at CERN and DESY. Results contributed to global combinations with LUX and PandaX-II, influencing developments in particle astrophysics and model building at institutions such as Princeton University and the Max Planck Society.

Collaboration and Timeline

The XENON Collaboration comprised universities and laboratories including Columbia University, University of Zurich, University of Oxford, INFN, and Rutherford Appleton Laboratory, coordinating project phases from commissioning through science runs between 2009 and 2016. Key milestones included detector commissioning, successive science runs yielding published limits in journals alongside presentations at conferences like Neutrino 2012 and ICRC, and transfer of technological lessons to successors such as XENON1T. The collaboration engaged with funding agencies including ERC and national science councils, concluding operations as larger-scale projects advanced the search for dark matter.

Category:Dark matter experiments