# IDM 2018

Jul 22 – 27, 2018
MacMillian
US/Eastern timezone

## Electron Recoil Bubble Nucleation in PICO Bubble Chambers

Jul 23, 2018, 2:40 PM
20m
117 (MacMillian)

### 117

#### MacMillian

Brown University Providence, Rhode Island, USA
Talk Direct Detection

### Speaker

Daniel Baxter (Northwestern University)

### Description

The primary advantage of the bubble chamber technology for dark matter detection, as used by the PICO collaboration, is its simultaneous sensitivity to nuclear recoils from dark matter interactions and insensitivity ($\sim 10^{-10}$) to electron recoil backgrounds. Previously published data in CF$_3$I indicated that the probability of nucleation for a single electron recoil scales with the thermodynamic threshold of the detector. More recent calibrations in C$_3$F$_8$ suggest that this may not be the case, indicating that the nucleation mechanisms in the two fluids may be different. I present separate nucleation models for energy deposition in C$_3$F$_8$ and on heavy atomic targets like iodine. These models fit existing PICO calibration data reasonably well, and should allow for more accurate prediction of electron recoil background rates in future PICO dark matter searches.

### Primary author

Daniel Baxter (Northwestern University)