# Energy deposition on nuclear emulsion by slow recoil ions for directional dark matter searches

## TL;DR

This paper evaluates energy deposition by slow recoil ions in nuclear emulsions, crucial for designing detectors for directional dark matter searches, by analyzing ion tracks, quenching factors, and background effects.

## Contribution

It provides detailed analysis of energy deposition and track structures of various recoil ions, enhancing the understanding for improved dark matter detector design.

## Key findings

- Electronic energy deposition varies with ion type and energy.
- Heavy recoil ions produce distinct track structures relevant for background discrimination.
- Proton track analysis informs neutron background mitigation strategies.

## Abstract

The electronic energy deposited on nuclear emulsions due to C ions of 5 -- 200~keV and Kr ions of 5 -- 600~keV are evaluated and compared with those due to fast ions for design and construction of fine grain nuclear emulsion for directional dark matter searches. Nuclear quenching factors and the electronic LET (linear energy transfer), the specific electronic energy deposited along the ion track, are evaluated. The so-called core and penumbra of heavy-ion track structure is modified for understanding the track due to recoil ions produced by dark matter candidate, WIMPs, striking nucleus in the AgBr crystal of nuclear emulsion. The very heavy recoil ions, 100 -- 180~keV Pb ions, produced in $\alpha$-decay are also studied. In addition, the track structures due to proton ions of 25 -- 80~keV are evaluated to consider the influence of background neutrons in underground laboratories.