CPF Seminar with Sharada Sahoo

Abstract:

Axions and axion-like particles (ALPs) are leading dark matter candidates, arising from symmetry-breaking mechanisms—axions from the Peccei-Quinn solution to the strong CP problem, and ALPs from other global symmetries. Their weak interaction with normal matter makes them suitable candidates for dark matter. Detecting them would not only provide critical insight into the nature of dark matter but also help address the strong CP problem within the Standard Model.

We aim to detect ALPs via their conversion into gamma rays. We have developed a scintillation detector based on thallium-doped cesium iodide (CsI (Tl)), chosen for its high gamma-ray absorption efficiency and high scintillation yield.  Initial experiments at the 1 MW TRIGA reactor at Texas A&M demonstrated the detector’s sensitivity to ALPs in the 0.1–10 MeV mass range, allowing us to probe regions near the unexplored "cosmological triangle" in ALP parameter space. Additionally, by employing radioactive sources such as Scandium-46, we can investigate the 0.1–1 MeV mass range and access the unexplored cosmological triangle. Beyond scintillation detectors, our group has also conducted a cryogenic reactor experiment using a sapphire detector equipped with phonon sensors. This setup targets lower-mass ALPs in the 3–75 keV range and has successfully excluded ALP candidates in previously explored regions.

Together, these photon- and phonon-based approaches cover a wide detection window from 3 keV to 10 MeV. Future experiments at the 85 MW High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory will further extend sensitivity in the 0.1–10 MeV range, enhancing our ability to probe the cosmological triangle. Additionally, plans to deploy the detector at Los Alamos National Laboratory in a high-intensity proton beam environment aim to explore new production channels and broaden the search for ALPs.

Bio:

Sharada Sahoo is a 4th year PhD candidate in Physics at Texas A&M University, with a BS-MS in Physics from NISER, India. His research focuses on building detectors for dark matter search experiments. He has experience working with detectors ranging from ~100 kg scintillation systems to ~100 g cryogenic phonon-only detectors. His expertise includes advanced data analysis using Python and machine learning. He has contributed to several conference presentations and a few publications.