Observation of the 'head-tail' effect in nuclear recoils of low-energy neutrons

TL;DR

This paper demonstrates an experimental method to detect the 'head-tail' directionality of nuclear recoils caused by low-energy neutrons, which is crucial for directional dark matter detection.

Contribution

The study introduces a novel technique using scintillation light detection in a low-pressure TPC to observe the 'head-tail' effect in nuclear recoils.

Findings

Successful tagging of recoil direction in neutron scattering

Observation of the 'head-tail' effect in low-energy nuclear recoils

Validation of the method for potential dark matter detection

Abstract

Directional detection of dark matter can provide unambiguous observation of dark matter interactions even in the presence of background. This article presents an experimental method to measure the direction tag ("head-tail") of the dark matter wind by detecting the scintillation light created by the elastic nuclear recoils in the scattering of dark matter particles with the detector material. The technique is demonstrated by tagging the direction of the nuclear recoils created in the scattering of low-energy neutrons with CF4 in a low-pressure time-projection chamber that is developed by the DMTPC collaboration. The measurement of the decreasing ionization rate along the recoil trajectory provides the direction tag of the incoming neutrons, and proves that the "head-tail" effect can be observed.