Channeling Effects in Direct Dark Matter Detectors

TL;DR

This paper estimates the fraction of channeled recoiling ions in NaI, Si, and Ge crystals in dark matter detectors, highlighting the temperature dependence and differences from injected ions, which impacts detection signals.

Contribution

It provides the first estimates of the channeling fraction of recoiling lattice nuclei in dark matter detectors using analytic models from past decades.

Findings

Channeling fraction is smaller for recoiling lattice nuclei than injected ions.

Channeling fraction is strongly temperature dependent.

Results impact interpretation of signals in direct dark matter detection experiments.

Abstract

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in NaI (Tl), Si and Ge crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects. We find that the channeling fraction of recoiling lattice nuclei is smaller than that of ions that are injected into the crystal and that it is strongly temperature dependent.