Experiments which search for dark matter particles are one of the critical science drivers for deep underground science. However, nuclear recoils from fast neutrons in underground laboratories are one of the most challenging backgrounds to possible dark matter detection and the rate of this background is poorly quantified. Dark matter experiments rely on numerical Monte Carlo simulations to predict the background rate due to these neutrons, yet the simulation of these processes is uncertain because of the lack of appropriate data for direct comparison.
This award will enable the PI to measure the neutron content and multiplicity of the showers produced by high energy cosmic rays by joining forces with the Case/UCSB Multiplicity Meter for Benchmarking Cosmogenic Neutron Backgrounds. By locating the Case/UCSB Gd-loaded scintillator detector under the muon shield, this group can cross-correlate hadronic showers sampled by the large area coverage of the muon system with the smaller, but more detailed, neutron-sensitive information from the Multiplicity Meter. The data on neutron multiplicity would allow the underlying neutron production processes to be measured, also providing information about the parent high-energy neutron spectrum. Together, the rate, multiplicity and energy measurements will help to normalize the simulation codes and provide insight into deficiencies in modeling the underlying processes.
The broader impacts of this work extend to the many other underground experiments that rely on knowing the neutron background environment. Being able to predict this background with greater reliability will serve the community well, and provide improved extrapolations for experiments aiming to operate in deeper sites at a future DUSEL. The technology used for the muon shield provides a training ground for a new generation of physicists with hands-on, short term projects.
