PICO (collaboration)

PICO (collaboration)
Name	PICO
Formation	2013
Type	Scientific collaboration
Purpose	Dark matter direct detection
Headquarters	United States
Region served	International

PICO (collaboration) is an international experimental collaboration focused on direct searches for dark matter using bubble chamber technology. The collaboration unites researchers from major institutions and laboratories to deploy detectors at underground facilities, aiming to detect weakly interacting massive particles (WIMPs) through nuclear recoil signatures. PICO builds on techniques developed in earlier experiments and interfaces with broader astroparticle physics efforts.

Overview

PICO brings together scientists from institutions such as Fermilab, Duke University, Simon Fraser University, TRIUMF, and Pacific Northwest National Laboratory to operate bubble chambers deployed at underground sites including SNOLAB, Sanford Underground Research Facility, and Deep Underground Neutrino Experiment. The collaboration's activities intersect with research programs at CERN, SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory, and partnerships with international universities like University of Chicago, Caltech, Massachusetts Institute of Technology, and Princeton University. PICO's detectors are influenced by prior experiments such as COUPP, PICASSO, CDMS, and LUX, and its results contribute to discussions alongside findings from XENON, PandaX, and SuperCDMS.

History and development

PICO formed by merging expertise from the COUPP and PICASSO collaborations, consolidating bubble chamber and superheated liquid techniques with support from agencies like the U.S. Department of Energy and the Natural Sciences and Engineering Research Council of Canada. Early milestones included commissioning prototypes inspired by R&D at Yale University, EFI (experimental facilities), and detector tests at facilities tied to Los Alamos National Laboratory and Brookhaven National Laboratory. The collaboration's timeline features deployments at SNOLAB and upgrades informed by technologies developed at TRIUMF and instrumentation groups at University of Toronto and Carnegie Mellon University. Collaborators have presented progress at conferences organized by American Physical Society, International Cosmic Ray Conference, and workshops hosted by CERN and KEK.

Instrumentation and detector design

PICO's detectors are bubble chambers using superheated fluorocarbon liquids such as C3F8 and CF3I housed in pressure vessels engineered with materials vetted at National Institute of Standards and Technology, Argonne National Laboratory, and industrial partners in collaboration with General Electric and specialized manufacturers. Acoustic sensors and piezoelectric transducers developed with contributions from Stanford University, University of Chicago, and Columbia University allow discrimination of nuclear recoils from alpha decays, building on calibration campaigns at Los Alamos National Laboratory and neutron beam facilities at NIST Center for Neutron Research. Low-background construction techniques involve screening at SNOLAB low-background counting facilities, mass spectrometry at Oak Ridge National Laboratory, and material assays coordinated with Gran Sasso National Laboratory partners. Data acquisition systems integrate electronics and firmware designed with expertise from MIT, University of California, Berkeley, and Princeton University, while simulation and analysis pipelines rely on codes used at CERN and modeling suites developed within groups associated with Harvard University and University of Cambridge.

Scientific goals and measurements

PICO aims to detect WIMP-induced nuclear recoils and to set leading constraints on spin-dependent and spin-independent WIMP-nucleon cross sections. The program targets parameter space highlighted by theories from researchers affiliated with Institute for Advanced Study, Perimeter Institute, University of Oxford, and model frameworks explored at Caltech, Stanford University, and University of California, Santa Cruz. Measurements include background characterization, neutron veto efficiency studies coordinated with SNOLAB and Sanford Lab teams, and searches for annual modulation signals considered in discussions with groups from Columbia University, University of Minnesota, and University of Zurich. Results inform global fits alongside complementary searches from AMS-02, Fermi Gamma-ray Space Telescope, and collider constraints from the Large Hadron Collider experiments ATLAS and CMS.

Collaboration structure and funding

The collaboration is governed by an executive board drawn from member institutions including Simon Fraser University, Duke University, Fermilab, TRIUMF, and University of Toronto, with scientific coordination linked to working groups that include participants from Caltech, Yale University, Harvard University, and MIT. Funding sources comprise national agencies such as the U.S. Department of Energy, the National Science Foundation, the Natural Sciences and Engineering Research Council of Canada, and institutional support from laboratories like SNOLAB and TRIUMF. International collaborations involve partners from Mexico's Universidad Nacional Autónoma de México, University of Chile, and European institutions such as University of Oxford and University of Zurich, with technical oversight provided by lab directors at Fermilab and TRIUMF.

Key results and publications

PICO has published leading limits on spin-dependent WIMP-proton interactions and competitive constraints on spin-independent cross sections using C3F8 chambers, reported in journals and conference proceedings read by researchers at APS, ICRC, and meetings at CERN. Key papers, authored by teams from Simon Fraser University, Duke University, and Fermilab, have been cited alongside results from XENON1T, LUX-ZEPLIN, and SuperCDMS in reviews produced by collaborators at Perimeter Institute and Institute for Advanced Study. The collaboration continues to release analysis updates, calibration studies, and technical design reports informing next-generation detectors and guiding strategies pursued at SNOLAB and future underground programs connected to DUNE and Hyper-Kamiokande.

Category:Particle physics collaborations