Direct Measurement of the Bubble Nucleation Energy Threshold in a CF3I Bubble Chamber

TL;DR

This paper introduces a novel method to directly measure the energy threshold for bubble nucleation in a CF3I bubble chamber, crucial for dark matter detection, using pion scattering to overcome calibration challenges.

Contribution

It presents a new technique employing pion scattering and silicon tracking to measure bubble nucleation thresholds in superheated fluids, validating CF3I's suitability for dark matter searches.

Findings

Measured bubble nucleation threshold at 13.6 keV with uncertainty

Results agree with classical bubble nucleation theory

Confirms CF3I as effective for spin-independent dark matter detection

Abstract

We have directly measured the energy threshold and efficiency for bubble nucleation from iodine recoils in a CF3I bubble chamber in the energy range of interest for a dark matter search. These interactions cannot be probed by standard neutron calibration methods, so we develop a new technique by observing the elastic scattering of 12 GeV/c negative pions. The pions are tracked with a silicon pixel telescope and the reconstructed scattering angle provides a measure of the nuclear recoil kinetic energy. The bubble chamber was operated with a nominal threshold of (13.6+-0.6) keV. Interpretation of the results depends on the response to fluorine and carbon recoils, but in general we find agreement with the predictions of the classical bubble nucleation theory. This measurement confirms the applicability of CF3I as a target for spin-independent dark matter interactions and represents a novel technique for calibration of superheated fluid detectors.