Columnar recombination: a tool for nuclear recoil directional sensitivity in a xenon-based direct detection WIMP search

Abstract

A robust signal for sidereal anisotropy in nuclear recoils would support, perhaps more decisively than any other evidence, a discovery claim for a WIMP component of Dark Matter. I present a concept based on columnar recombination in dense xenon gas, sensing nuclear recoil direction relative to a TPC drift field. The central advance is that nuclear recoil directionality information is obtained through a comparison, event-by-event, of the ionization signal and recombination signal that are produced prior to drifting the track ionization. The optimum xenon density for this concept may be near ten bars, unlike conventional techniques that employ track visualization – with severe restrictions on gas density to about 1/10 bar. No restriction is imposed by diffusion during drift, facilitating the realization of a large monolithic room temperature xenon gas Time Projection Chamber at the ton-scale, with unprecedented sensitivity for both directionality and cross-section. Remarkably, the desired operating conditions for 0-νββ 136Xe experiment may be identical.