PICO-60

PICO-60
Name	PICO-60
Caption	Bubble chamber used in dark matter search
Type	Direct detection dark matter experiment
Location	SNOLAB, Ontario, Canada
Status	Completed
Operation	2013–2017
Detector	Superheated liquid bubble chamber
Target	C3F8 (perfluoropropane)
Collaboration	PICO Collaboration

PICO-60

PICO-60 was a direct-detection dark matter experiment that operated a bubble chamber at an underground site to search for weakly interacting massive particles. The apparatus combined cryogenic techniques, acoustic readout, and radiopure materials to probe spin-dependent and spin-independent interactions. The project drew on expertise across particle astrophysics, low-background techniques, and underground laboratory operations.

Introduction

PICO-60 was developed to test theoretical predictions about dark matter candidates motivated by studies associated with Weakly Interacting Massive Particle, Supersymmetry, Minimal Supersymmetric Standard Model, Kaluza–Klein theory, and extensions proposed in the context of Large Hadron Collider phenomenology. The collaboration leveraged infrastructure at the SNOLAB facility and collaborations with groups that contributed to experiments such as LUX-ZEPLIN, Super-Kamiokande, SNO, XENON1T, and DEAP-3600. The detector addressed questions raised following results from experiments like CDMS II, DAMA/LIBRA, CoGeNT, and CRESST-II.

Detector Design and Operation

The detector used a superheated liquid bubble chamber design descended from devices used in searches pioneered by teams at Fermilab, Brookhaven National Laboratory, and institutions with histories linked to Lawrence Berkeley National Laboratory and TRIUMF. The active target was the perfluorocarbon liquid C3F8, instrumented with acoustic sensors and optical cameras, and enclosed in a pressure vessel built to standards similar to hardware produced for CERN experiments. Operation relied on cycles of compression and decompression coordinated with cryogenic systems akin to those used at Gran Sasso National Laboratory and Laboratori Nazionali del Gran Sasso. Control and monitoring systems interfaced with software frameworks developed by groups that previously worked on ATLAS, CMS, and NOνA.

Calibration and Background Suppression

Calibration campaigns used neutron sources and gamma calibrations comparable to procedures employed by KamLAND, Borexino, Daya Bay, and Double Chooz to map response to nuclear recoils and electron recoils. Background suppression drew on radiopurity techniques practiced at Lawrence Livermore National Laboratory and materials screening done at facilities such as SNOLAB and the United States Department of Energy low-background counting facilities. The collaboration implemented acoustic discrimination methods informed by acoustic analysis developments at University of Chicago and MIT, and veto strategies coordinated with muon veto techniques used by IceCube and ANTARES.

Scientific Results and Limits

PICO-60 published constraints on spin-dependent WIMP-proton and spin-independent WIMP-nucleon cross sections that contributed to the global picture alongside limits reported by PandaX, DarkSide-50, XENON100, and LUX. Results were interpreted in the context of phenomenological models discussed in literature from groups at University of California, Berkeley, Harvard University, Princeton University, and Stanford University. The limits informed theoretical work associated with researchers at CERN, Perimeter Institute, and Institute for Advanced Study, and intersected with indirect detection constraints from Fermi Gamma-ray Space Telescope analyses and collider constraints from ATLAS and CMS searches.

Upgrades and Successor Experiments

Following the PICO-60 campaign, the collaboration and allied institutions developed plans for larger, more sensitive detectors that built on experience from PICO-60 and projects such as PICO-500 proposals, drawing conceptual and technical links to future phases of LUX-ZEPLIN and next-generation detectors discussed in workshops at DESY and KEK. Engineering lessons influenced detector design discussions at SLAC National Accelerator Laboratory and informed proposals submitted to funding agencies including Natural Sciences and Engineering Research Council of Canada and agencies in the United States Department of Energy.

Collaboration and Funding

The PICO collaboration comprised scientists from universities and national laboratories with histories at University of Alberta, Queen's University, Carnegie Mellon University, Yale University, Pennsylvania State University, University of Chicago, Indiana University Bloomington, Los Alamos National Laboratory, and other institutions that have participated in major experiments like MINOS and NOvA. Funding and logistical support were provided by agencies and organizations such as the Natural Sciences and Engineering Research Council of Canada, the National Science Foundation (United States), the Department of Energy (United States), and institutional grants tied to national laboratories. The collaboration coordinated with underground laboratory management at SNOLAB and engaged with international advisory panels including members associated with CERN committees and dark matter review panels convened by agencies in Canada and the United States.

Category:Particle detectors Category:Dark matter experiments