GRAMS (Gamma-Ray and AntiMatter Survey) is a proposed next-generation experiment that aims both astrophysical observations with MeV gamma rays and indirect dark matter searches with antimatter using a LArTPC (Liquid Argon Time Projection Chamber) detector. With a cost-effective, large scale LArTPC detector, GRAMS can extensively probe astrophysical objects in the poorly-explored MeV energy region. The GRAMS sensitivity to MeV gamma rays can be an order of magnitude improved with a single balloon flight, compared with the previous experiments while the satellite mission can be comparable to the future proposed missions. The project could potentially be the first to detect MeV gamma rays from neutron star mergers associated with gravitational waves as well as from Galactic neutron star merger remnants. The GRAMS antimatter survey can provide background-free dark matter signatures, which may allow us to verify the possible dark matter detection reported by Fermi and AMS-02. Large-scale, low-noise noble liquid detectors have been successfully employed in neutrino and dark matter search experiments and we are currently developing the LArTPC detector for a balloon mission as well as the event reconstruction algorithm for MeV gamma-ray detection and background rejection techniques.


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