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New results on the detection of axions and galaxy axion-like particles(ALPs) with 80 day of PandaX-II data were published online in Physical Review Letters on Nov 1, 2017 (on the same issue with another PandaX-II paper on54 ton-day WIMP search results). No positive signal was found by the most sensitive detector all over the world, so that the most stringentconstraints on the properties of axion and ALPs were set.

Axion is a new type of particle which was proposed by Steven Weinberg and Frank Wilczek in late 1970s to explain the CP conservation in strong interactions. It is also one of the top candidates of dark matter particles in our universe. According to the theory, axions may interact with electrons and transfer all their energy to the electrons. By measuring the energetic electrons in the final state, experimentalist may determine the mass and coupling constant of axions with electrons.

PandaX-II is one of the largest running dark matter direct detection experiments. It uses high purity xenon as the detection medium. The PandaX-II detector is sensitive in the searching of rare events within the energy region around several keV. In this analysis, PandaX-II obtained the world leading results with about 80 days of data.The upper limit on the coupling between the solar axionand electron was set to be less than 4.35×10^-12 when the axion mass is smaller than 1keV.The limit on that of galactic ALPs is on the order of 1×10^-13, for ALPs in the mass range of 1-10 keV.

paper link：https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.181806