Determining the bubble nucleation efficiency of low-energy nuclear recoils in superheated C${}_3$F${}_8$ dark matter detectors

Abstract

The bubble nucleation efficiency of low-energy nuclear recoils in superheated liquids plays a crucial role in interpreting results from direct searches for weakly interacting massive particle (WIMP) dark matter. The PICO Collaboration presents the results of the efficiencies for bubble nucleation from carbon and fluorine recoils in superheated C${}_3$F${}_8$ from calibration data taken with 5 distinct neutron spectra at various thermodynamic thresholds ranging from 2.1 keV to 3.9 keV. Instead of assuming any particular functional forms for the nuclear recoil efficiency, a generalized piecewise linear model is proposed with systematic errors included as nuisance parameters to minimize model-introduced uncertainties. A Markov-Chain Monte-Carlo (MCMC) routine is applied to sample the nuclear recoil efficiency for fluorine and carbon at 2.45 keV and 3.29 keV thermodynamic thresholds simultaneously. The nucleation efficiency for fluorine was found to be $\ge 50\%$ for nuclear recoils of 3.3 keV (3.7 keV) at a thermodynamic Seitz threshold of 2.45 keV (3.29 keV), and for carbon the efficiency was found to be $\ge 50\%$ for recoils of 10.6 keV (11.1 keV) at a threshold of 2.45 keV (3.29 keV). Simulated data sets are used to calculate a p-value for the fit, confirming that the model used is compatible with the data. The fit paradigm is also assessed for potential systematic biases, which although small, are corrected for. Additional steps are performed to calculate the expected interaction rates of WIMPs in the PICO-60 detector, a requirement for calculating WIMP exclusion limits.

17 pages, 22 figures, 5 tables

References in corpus (6)

• First dark matter search results from a 4-kg CF${}_3$I bubble chamber operated in a deep underground site
• Dark Matter Search Results from the Complete Exposure of the PICO-60 C${}_3$F${}_8$ Bubble Chamber
• Dark Matter Search Results from the PICO-2L C${}_3$F${}_8$ Bubble Chamber
• Final Results of the PICASSO Dark Matter Search Experiment
• First Results of the Phase II SIMPLE Dark Matter Search
• New Insights into Particle Detection with Superheated Liquids

Cited by in corpus (6)

• Low-threshold response of a scintillating xenon bubble chamber to nuclear and electronic recoils
• Model for bubble nucleation efficiency of low-energy nuclear recoils in bubble chambers for dark matter detection
• Absorption of Fermionic Dark Matter in the PICO-60 C${}_3$F${}_8$ Bubble Chamber
• The ionization yield in a methane-filled spherical proportional counter
• Interfacial Line Energy of a Topological Phase
• Nuclear Recoil Identification in a Scientific Charge-Coupled Device