Intrinsic neutron background of nuclear emulsions for directional Dark Matter searches

Abstract

Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. This im- provement opens the way to a directional Dark Matter detection, thus providing an innovative and com- plementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we pro- vide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out thresh- old, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure

Supernova neutrino physics with a nuclear emulsion detector

“…This study has also shown that the neutron-induced events can be reduced down to 0.06 kg −1 y −1 exploiting directionality and track length cuts. This result was obtained without any purification of the materials involved [37]. Nowadays ton-scale detectors for direct dark matter search have made the external neu-tron background negligible using appropriate shields.…”

“…The main background sources is therefore induced by neutrons. Neutron-induced recoils from intrinsic contamination in NIT emulsions were recently evaluated with a GEANT4 simulation, giving a yield of ∼ 1 neutron kg −1 y −1 [37]. This study has also shown that the neutron-induced events can be reduced down to 0.06 kg −1 y −1 exploiting directionality and track length cuts.…”

Directional Dark Matter Search with Nuclear Emulsion

“…A pilot experiment will be performed with the exposure of 10 kg mass target on a time scale of one year with the aim of measuring the detectable background from environmental and intrinsic sources and to validate estimates from measurements [16] and simulations. The confirmation of a negligible background will pave the way for the construction of a pilot experiment with an exposure on the ∼10 kg year scale, which will act as a demonstrator to further extend the sensitivity towards the neutrino floor.…”

“…The intrinsic emulsion radioactivity, instead, has been evalutated by using a dedicated MC simulation based on the SOURCES code [15] and a GEANT4-based simulation. The detectable neutron-induced background would be 0.06 n/yr/kg [16].…”

Alternative Uses for Quantum Systems and Devices

“…Detectors for anisotropic ultraenergetic cosmic rays of galactic origin are schematized in References [26][27][28]; the dark-matter-induced symmetry violations are examined in [29].…”