Channeling in direct dark matter detection I: channeling fraction in NaI (Tl) crystals

TL;DR

This paper estimates the fraction of channeled recoiling ions in NaI(Tl) crystals, showing it is lower than for injected ions and highly temperature-dependent, impacting dark matter detection signals.

Contribution

It applies historical analytic models to estimate the channeling fraction in NaI(Tl) crystals, providing new insights into temperature dependence and recoil behavior.

Findings

Channeling fraction is smaller for recoiling nuclei than injected ions.

Channeling fraction strongly depends on temperature.

Results impact interpretation of dark matter detection signals.

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) 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.