Abstract
Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (approx 11 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.
Highlights
Directional detection is one of the research frontiers on weakly interacting dark matter particles (WIMPs) and several techniques are being studied and developed
In a recent paper [1,2], it has been proposed that large arrays of aligned carbon nanotubes (CNTs) might be of use as target material for the directional detection of Dark Matter (DM) Weakly Interacting Massive Particles (WIMPs)
The purpose of this paper is to illustrate the dynamics in these regions and, by means of Monte Carlo (MC) simulations, to provide an evaluation of the “channeling efficiency” of a large number of CNT arrays as the target of a directional DM detector
Summary
Directional detection is one of the research frontiers on WIMPs and several techniques are being studied and developed. In a recent paper [1,2], it has been proposed that large arrays of aligned carbon nanotubes (CNTs) might be of use as target material for the directional detection of Dark Matter (DM) Weakly Interacting Massive Particles (WIMPs). For nanotube radii much larger than the typical C electron orbital size, the potential can be well approximated by a step barrier In this approximation, CNTs are considered as full solid cylinders, totally reflecting those ions having the right initial conditions, namely a transverse energy lower than the continuum potential barrier [1,2, Fig. 4]. In [1,2], a new type of directional detector was outlined It consists of large arrays of CNTs which provide the target material for WIMP-nuclei collisions and an anisotropic sensitivity to the recoil direction, complemented by a readout technique to detect the emitted nuclei. Given the relatively low mass of the C nuclei, such detector would extend the WIMP search to low masses (≈10 GeV) if a suitable ion detection threshold of few KeV might be attained
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