Model for bubble nucleation efficiency of low-energy nuclear recoils in bubble chambers for dark matter detection

Abstract: Bubble chambers are promising technologies for detecting low-energy nuclear recoils from the elastic scattering of dark matter particle candidates. Bubble nucleation occurs when the energy deposition exceeds a specific threshold defined traditionally by the "heat-spike" Seitz threshold. In this paper, we report on a physical model that can account for observed discrepancies between the current Seitz model and the measured nucleation efficiency of low-energy nuclear recoils, which is necessary for interpreting dark matter signals. In our work, we combine molecular dynamics and Monte Carlo simulations together with the Lindhard model to predict bubble nucleation efficiency and energy thresholds for C$_3$F$_8$, CF$_3$I, and xenon with enhanced accuracy over the Seitz model when compared to existing experimental data. We use our model to determine the effect on cross-section limits for spin-dependent and spin-independent interactions and compare it to the current PICO dark matter experiment. Our technique can also be applied to estimate the efficiency of future target fluids where no experimental data are available. As an example, we predict the nucleation efficiency, the energy threshold and the cross-section limits in the spin-independent channel for the Scintillating Bubble Chamber experiment filled with superheated liquid argon.