Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the α ′ /α parameter related to kinetic mixing of hidden photons and the coupling constant g Ae of axion-like particles in the mass range from 40 to 120 keV/c 2 , resulting in α ′ /α < 6 × 10 −26 and g Ae < 4 × 10 −13 . These limits are the most stringent over this mass range derived from both direct and indirect searches to date.

A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We have used 705.9 live days of data in a fiducial volume containing 97 kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was (4.2 ± 0.2) × 10 −3 day −1 kg −1 keV −1 ee at 5 keV ee , with a signal efficiency of 20%. All the remaining events are consistent with our background evaluation, mostly of the "mis-reconstructed events" originated from 210 Pb in the copper plates lining the detector's inner surface. The obtained upper limit on a spinindependent WIMP-nucleon cross section was 2.2 × 10 −44 cm 2 for a WIMP mass of 60 GeV/c 2 at the 90% confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors.

The cosmic-ray flux into the Earth atmosphere fluctuates over time due to various factors. Solar and geomagnetic modulation of galactic cosmic rays are dominating this process on timescales from a few-days to millions of years, such as Forbush decreases (a shielding of galactic cosmic rays due to a coronal mass ejection), the 11-year Schwabe cycle, multidecadal variation such as Grand Solar Minima, or millennial variations in Earth's magnetic field strength. In addition to these recurring factors, sporadic and intense solar energetic particle (SEP) events can also contribute to a sudden ejection of cosmic rays to the Earth. A large-scale SEP event reaching Earth is known as a ground level enhancement (GLE), which can be detected as a large increase in the count rates of ground-based neutron monitors. Since 1942, 72 GLEs have been recorded (1: GLE database). Prior to direct observations of cosmic rays, signatures of past extreme SEP events can be recorded by cosmogenic nuclides, in particular, 14 C in tree rings, and 10 Be and 36 Cl in polar ice cores, all of which are produced in a particle cascade triggered by interactions of high energy cosmic rays with the constituents of Earth's lower atmosphere (Mekhaldi et al., 2015;Miyake, Usoskin, & Poluianov, 2019).Conceivable SEP-driven cosmic ray events reported so far in multiple studies are the 774/775 CE (Bünt-

An annual modulation signal due to the Earth orbiting around the Sun would be one of the strongest indications of the direct detection of dark matter. In 2016, we reported a search for dark matter by looking for this annual modulation with our single-phase liquid xenon XMASS-I detector. That analysis resulted in a slightly negative modulation amplitude at low energy. In this work, we included more than one year of additional data, which more than doubles the exposure to 800 live days with the same 832 kg target mass. When we assume weakly interacting massive particle (WIMP) dark matter elastically scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon cross section was improved by a factor of 2 to 1.9×10 −41 cm 2 at 8 GeV/c 2 at 90% confidence level with our newly implemented data selection through a likelihood method. For the model-independent case, without assuming any specific dark matter model, we obtained more consistency with the null hypothesis than before with a p-value of 0.11 in the 1−20 keV energy region. This search probed this region with an exposure that was larger than that of DAMA/LIBRA. We also did not find any significant amplitude in the data for periodicity with periods between 50 and 600 days in the energy region between 1 to 6 keV.

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