Research

Overview

I am an Assistant Professor in the Department of Physics and the Center for Experimental Nuclear Physics and Astrophysics (CENPA) at the University of Washington, Seattle. My current research is on the search for dark matter and neutrinoless ββ decay. My laboratories are in rooms B059 in the Physics and Astronony Building (PAB) and 165 in the North Physics Lab (NPL).

DAMIC: Dark Matter in CCDs

The nature of dark matter is one of the biggest problems in cosmology and all of science. Dark matter is a massive substance whose existence has been inferred from its gravitational effects on the dynamics of stars, galaxies, clusters of galaxies and the expansion of the universe. However, the fundamental nature of dark matter remains unexplained. The answer (or lack of answer) to this question may have profound implications on the philosophical underpinnings of science, e.g., what is matter? The atomist world-view of particle physics suggests that matter is made of fundamental building blocks, i.e., particles. The reductionist world-view suggests that all particles have a common origin in the Big Bang and, at some level, interact with one another.  Hence, dark matter is hypothesized to be made of some yet undiscovered particle that interacts, albeit weakly, with ordinary matter.

The DAMIC Collaboration deploys scientific charge-coupled devices (CCDs) in a low-radiation environment underground to look for the faint signals from possible interactions of dark matter particles in the Milky Way halo with the bulk matter (i.e., nuclei and electrons) of the CCDs. Our devices are the lowest noise ionization detectors ever developed, and the most massive CCDs ever built. The high spatial resolution of the CCDs (pixel size 15 x 15 μm²) allows for unique background rejection capabilities. We have a seven-CCD array currently operating, with a fifty-CCD array (one-kilogram target mass) under development. The main goal of the DAMIC program is to achieve the world's best sensitivity in the search for dark matter particles with masses as small as the electron's and as heavy as ten times the proton mass. For more information, please visit the DAMIC research page at CENPA.

Selena R&D

A well studied natural process is ββ decay, where a nuclear transmutation occurs spontaneously with the emission of two electrons and two antineutrinos, e.g., ⁸²Se  → ⁸²Kr + 2e^- + 2ν̅. This process is of particular interest for nuclear physicists because a straightforward extension of the Standard Model of particle physics proposes that neutrinos (the only uncharged fermion) are their own antiparticles. Hence, it could be possible for the emitted antineutrinos to "annihilate" in the nuclear environment, leading to the decay  ⁸²Se  → ⁸²Kr + 2e^-, so-called "neutrinoless" ββ decay. This process violates conservation of lepton number, one of the assumed symmetries of nature.

The signature of this process is the emission of two electrons from a single nucleus, which, in the absence of the antineutrinos, carry the full energy released in the decay. Selena is an R&D program to develop hybrid amorphous ⁸²Se / CMOS imagers that can resolve with high spatial and energy resolution the tracks of the emitted electrons for unparalleled sensitivity to the signal. It builds upon existing amorphous Se x-ray imaging technology and the particle identification capabilities developed for DAMIC. For more information, please see the concept paper.

Past

My PhD work was on nuclear astrophysics, where I contributed to the most detailed measurements of the solar neutrino spectrum with the Borexino detector. These results confirmed our understanding of the nuclear reactions in the sun and the fundamental properties of massive neutrinos as they travel in the dense solar matter and transition into empty space.