The Mega electron volt (MeV) gamma-ray observation is a promising diagnostic tool for observing the universe. However, the sensitivity of MeV gamma-ray telescopes is limited due to peculiar backgrounds, restricting the application of MeV gamma rays for observation. Identification of backgrounds is crucial for designing next-generation telescopes. Therefore, herein, we assessed the background contribution in the electron-tracking Compton camera (ETCC) on board the SMILE- 2+ balloon experiment. This assessment was performed using the Monte Carlo simulation. The results revealed that the background below 400 keV existed due to the atmospheric gamma-ray background, the cosmic-ray/secondary-particle background, and the accidental background. On the other hand, the unresolved background component, which was not likely to be relevant to direct Compton-scattering events in the ETCC, was confirmed above 400 keV. Overall, this study demonstrated that the Compton-kinematics test provides a powerful tool to remove the background and principally improves the signal-to-noise ratio at 400 keV by an order of magnitude.
@article{arxiv.2306.02700,
title = {Background contributions in the electron-tracking Compton camera onboard SMILE-2+},
author = {Tomonori Ikeda and Atsushi Takada and Taito Takemura and Kei Yoshikawa and Yuta nakamura and Ken Onozaka and Mitsuru Abe and Toru Tanimori},
journal= {arXiv preprint arXiv:2306.02700},
year = {2024}
}