The GRAMS mission for MeV gamma-ray astronomy and dark matter search

GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation proposed balloon-borne/satellite-based mission aimed at high sensitivity MeV gamma-ray astrophysical observations and background-free indirect dark matter search via hadronic antiparticles. The main detector of GRAMS is a meter-scale liquid argon time projection chamber (LArTPC). The adoption of liquid argon as detector material allows us to produce an unprecedentedly large effective area instrument both for cosmic MeV gamma rays of 0.5-20 MeV and antiparticles of dark matter origin. This large effective area, which will exceed 1000 cm2, is necessary for measuring faint gamma-ray signals of nuclear line emissions from energetic phenomena such as supernovae as well as for observing short-duration transient objects including gamma-ray bursts with high photon statistics. In this talk, we present the mission concept and design, the current proof-of-concept studies using prototype LArTPCs, and an engineering balloon flight conducted in 2023.