EAGER: Direct Detection of MeV-Scale Dark Matter Utilizing Germanium Internal Amplification for the Charge Created by the Ionization of Impurities

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Multiple astronomical observations have established that about 85% of the matter in the universe is not made of known elementary particles. Deciphering the nature of this so-called Dark Matter (DM) is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. One of the most exciting quests is the search for new particles beyond the Standard Model of Particle Physics, which describes all the known elementary particles and the interactions between them. Extensions of the model predict not only new particles with large masses but also some with very small masses. The general properties of neutrinos and the nature of DM are currently two of the most important questions in fundamental physics. This EAGER award will explore a new germanium (Ge) detector technology utilizing Charge Internal Amplification (GeCIA) for the charge carriers created by the ionization of impurities, which is a promising new technology with experimental sensitivity for detecting MeV-scale dark matter.Novel direct-detection strategies to probe non-gravitational interactions between DM and ordinary matter are needed to discover DM. The broad resources gained through this exploratory work will enable the development of next generation detectors that meet sensitivity requirements in a cost-effective manner. The techniques developed will have immediate application to several experiments, including the DM program and low energy neutrino program in the U.S. and elsewhere in the world. Equally important and central to the planned activities is its work to develop the next generation of diverse workers. One female postdoc will fully work on the project and become expertise in developing GeCIA detectors. In addition, three PhD students will also work on the project.GeCIA will adopt a phased approach to build an experiment at Sanford Underground Research Facility (SURF) to directly search for DM with a mass range from 0.1 MeV to 1 GeV. GeCIA-0 is an exploratory project that will innovate GeCIA detectors at a mass of 300 grams to demonstrate the technology for a p-type planar geometry. They will fabricate a planar detector with amorphous Ge (a-Ge) contact technology, which has been successfully used to fabricate detectors at USD with home-grown crystals. This funding will support the group to (1) optimize the design of such a planar detector with Monte Carlo simulation; (2) fabricate a planar detector with a-Ge contact technology; (3) prove GeCIA technology with appropriate electronic read-out system; and (4) calibrate detectors with optical and low energy radiative sources.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.