GAPS: The Balloon Borne Dark Matter Search Experiment
Jan. 28, 2025 | Aerospace Project Research Associate, ISAS people
AOYAMA Kazutaka / Dept. of Interdisciplinary Space Science, ISAS
Research Summary
I am conducting research as part of the GAPS (General Antiparticle Spectrometer) experiment, which aims to elucidate the true nature of dark matter—one of the most fundamental mysteries of the physics. This experiment employs a high-altitude balloon flying in the stratosphere over Antarctica.
Ordinary matter, which constitutes only about 5% of the universe, is the visible material that we can observe. In contrast, approximately 27% of the universe is believed to be composed of dark matter. The presence of this invisible substance has been inferred through astronomical phenomena; however, its nature remains unknown. The GAPS experiment aims to detect signatures of dark matter annihilation or decay by detecting rare antiparticles such as antiprotons and antideuterons.
To achieve this, the GAPS experiment employs a novel detection method based on the formation and subsequent decay of exotic atoms. Unlike conventional detectors that rely primarily on magnetic fields to determine particle identity via curvature, GAPS detects antiparticles by allowing them to slow down and stop within a layered silicon (Si) semiconductor tracker. Once at rest, these antiparticles are captured by Si nuclei to form exotic atoms. The decay of these exotic atoms produces characteristic de-excitation X-rays and a hadronic cascade*1, which are both measured to unambiguously identify the particle species.
By deploying the detector on a scientific balloon operating at altitudes around 36 km, the experiment minimizes atmospheric interference. Moreover, the Antarctic summer provides a stable circumpolar airflow that facilitates long-duration observations, while the low geomagnetic influence in polar regions allows efficient detection of charged particles. Since joining JAXA/ISAS, I have contributed to the assembly and operation of the GAPS detector both in the United States and Antarctica, as well as to the analysis of data acquired during the preparation phase. As of this writing, preparations are ongoing on the Antarctic ice for the science flight scheduled in JFY2024. I am primarily responsible for the construction and operation of the cooling system for the Si detector. Additionally, I analyze test data obtained on the ground to assess the health and functionality of the detector. Moving forward, I will analyze observation data obtained from this Antarctic flight to further the quest for understanding the nature of dark matter.
Terminologies
- *1 Hadronic cascade refers to a chain reaction of interactions involving hadrons—particles made of quarks, such as protons, neutrons, and pions