We report a new search for weakly interacting massive particles (WIMPs) using the combined low background data sets acquired in 2016 and 2017 from the PandaX-II experiment in China. The latest data set contains a new exposure of 77.1 live days, with the background reduced to a level of 0.8×10^{-3}  evt/kg/day, improved by a factor of 2.5 in comparison to the previous run in 2016. No excess events are found above the expected background. With a total exposure of 5.4×10^{4}  kg day, the most stringent upper limit on the spin-independent WIMP-nucleon cross section is set for a WIMP with mass larger than 100  GeV/c^{2}, with the lowest 90% C.L. exclusion at 8.6×10^{-47}  cm^{2} at 40  GeV/c^{2}.

We report the WIMP dark matter search results using the first physics-run data of the PandaX-II 500 kg liquid xenon dual-phase time-projection chamber, operating at the China JinPing underground Laboratory. No dark matter candidate is identified above background. In combination with the data set during the commissioning run, with a total exposure of 3.3×10 4 kg-day, the most stringent limit to the spin-independent interaction between the ordinary and WIMP dark matter is set for a range of dark matter mass between 5 and 1000 GeV/c 2 . The best upper limit on the scattering cross section is found 2.5 × 10 −46 cm 2 for the WIMP mass 40 GeV/c 2 at 90% confidence level.Weakly interacting massive particles, WIMPs in short, are a class of hypothetical particles that came into existence shortly after the Big Bang. The WIMPs could naturally explain the astronomical and cosmological evidences of dark matter in the Universe. The weak interactions between WIMPs and ordinary matter could lead to the recoils of atomic nuclei that produce detectable signals in deep-underground direct detection experiments. Over the past decade, the dual-phase xenon time-projection chambers (TPC) emerged as a powerful technology for WIMP searches both in scaling up the target mass, as well as in improving background rejection [1][2][3]. LUX, a dark matter search experiment with a 250 kg liquid xenon target, has recently reported the best limit of 6×10 −46 cm 2 on the WIMP-nucleon scattering cross section [4] The PandaX-II experiment, a half-ton scale dual-phase xenon experiment at the China JinPing underground Laboratory (CJPL), has recently reported the dark matter search results from its commissioning run (Run 8,19.1 live days) with a 5845 kg-day exposure [5]. The data were contaminated with significant 85 Kr background. After a krypton distillation campaign in early 2016, PandaX-II commenced physics data taking in March 2016. In this paper, we report the combined WIMP search results using the data from the first physics run from March 9 to June 30, 2016 (Run 9, 79.6 live days) and Run 8, with a total of 3.3×10 4 kg-day exposure, the largest reported WIMP data set among dual-phase xenon detectors in the world to date.The PandaX-II detector has been described in detail in Ref. [5]. The liquid xenon target consists of a cylindrical TPC with dodecagonal cross section (opposite-side distance 646 mm), confined by the polytetrafluoroethylene (PTFE) reflective wall, and a vertical drift distance of 600 mm defined by the cathode mesh and gate grid located at the bottom and top. For each physical event, the prompt scintillation photons (S1) and the delayed electroluminescence photons (S2) from the ionized electrons are collected by two arrays of 55 Hamamatsu R11410-arXiv:1607.07400v3 [hep-ex] Hamamatsu R8520-406 1-inch PMTs serving as an active veto. The γ background, which produces electron recoil (ER) events, can be distinguished from the dark matter nuclear recoil (NR) using the S2-to-S1 ratio. During the data taking period in Run 9, a few diffe...

The PandaX-4T experiment, a four-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in this experiment. In a 2.8-ton fiducial mass and the signal region between 1 to 10 keV electron equivalent energy, the total electron recoil background is found to be 4.9 · 10 −5 (kg · day · keV) −1 . The nuclear recoil background in the same region is 2.8 · 10 −7 (kg · day · keV) −1 . With an exposure of 5.6 ton-years, the sensitivity of PandaX-4T could reach a minimum spin-independent dark matter-nucleon cross section of 6 · 10 −48 cm 2 at a dark matter mass of 40 GeV/c 2 .

We report new searches for solar axions and galactic axionlike dark matter particles, using the first low-background data from the PandaX-II experiment at China Jinping Underground Laboratory, corresponding to a total exposure of about 2.7×10^{4}  kg day. No solar axion or galactic axionlike dark matter particle candidate has been identified. The upper limit on the axion-electron coupling (g_{Ae}) from the solar flux is found to be about 4.35×10^{-12} in the mass range from 10^{-5} to 1  keV/c^{2} with 90% confidence level, similar to the recent LUX result. We also report a new best limit from the ^{57}Fe deexcitation. On the other hand, the upper limit from the galactic axions is on the order of 10^{-13} in the mass range from 1 to 10  keV/c^{2} with 90% confidence level, slightly improved compared with the LUX.

We present the results of a search for WIMPs from the commissioning run of the PandaX-II experiment located at the China Jinping underground Laboratory. A WIMP search data set with an exposure of 306×19.1 kg-day was taken, while its dominant 85 Kr background was used as the electron recoil calibration. No WIMP candidates are identified, and a 90% upper limit is set on the spin-independent elastic WIMP-nucleon cross section with a lowest excluded cross section of 2.97×10 −45 cm 2 at a WIMP mass of 44.7 GeV/c 2 .PACS numbers: 95.35.+d, 29.40.-n, 95.55.Vj

No abstract

New constraints are presented on the spin-dependent WIMP-nucleon interaction from the PandaX-II experiment, using a data set corresponding to a total exposure of 3.3×10 4 kg-days. Assuming a standard axial-vector spin-dependent WIMP interaction with 129 Xe and 131 Xe nuclei, the most stringent upper limits on WIMP-neutron cross sections for WIMPs with masses above 10 GeV/c 2 are set in all dark matter direct detection experiments. The minimum upper limit of 4.1 × 10 −41 cm 2 at 90% confidence level is obtained for a WIMP mass of 40 GeV/c 2 . This represents more than a factor of two improvement on the best available limits at this and higher masses. These improved cross-section limits provide more stringent constraints on the effective WIMP-proton and WIMP-neutron couplings.The existence of dark matter (DM) in the Universe has been established by numerous pieces of astronomical and cosmological evidence. These range from the dynamics, gravitational lensing, and clustering of galaxies to the necessity of DM to explain the power spectrum of the cosmic microwave background and the formation of cosmological structures. However, the particle nature of DM still remains elusive. Weakly interacting massive particles (WIMPs), a class of hypothetical particles predicted by many extensions of the Standard Model of particle physics, are promising candidates for DM. Generic WIMP production and annihilation rates in the early universe would lead to a freeze-out WIMP density which could explain the observed DM relic density (the so-called "WIMP miracle" [1] , which is being prepared, will search for neutrinoless double beta decay of 136 Xe. PandaX-I, with a 120-kg xenon target, was completed in 2014. PandaX-II, with a half-ton xenon target, has been running since the end of 2015. Both the PandaX-I and PandaX-II experiments use a dual-phase xenon time projection chamber technique. With this technique, both the prompt scintillation photons (S1) produced in liquid xenon and the delayed electroluminescence photons (S2) produced in gaseous xenon for each physical event can be measured. This leads to powerful background suppression and signal-background discrimination. More detailed descriptions of the PandaX-I and PandaX-II experiments can be found in Refs. [3][4][5][6]. The PandaX-II collaboration has recently reported WIMP search results [6] using the first 98.7 days of data. This data set corresponds to a total exposure of 3.3×10 4 kg-days. No excess of events was observed above the background, and WIMP-nucleon cross-section upper limits were set assuming a spin-independent (SI) WIMP-nucleon interaction. The best upper limit of 2.5 × 10 −46 cm 2 for a WIMP mass of 40 GeV/c 2 was obtained. In this paper we consider an axial-vector, arXiv:1611.06553v3 [hep-ex]

We search for nuclear recoil signals of dark matter models with a light mediator in PandaX-II, a direct detection experiment in the China Jinping underground laboratory. Using data collected in 2016 and 2017 runs, corresponding to a total exposure of 54 ton day, we set upper limits on the zero-momentum dark matter-nucleon cross section. These limits have a strong dependence on the mediator mass when it is comparable to or below the typical momentum transfer. We apply our results to constrain self-interacting dark matter models with a light mediator mixing with standard model particles, and set strong limits on the model parameter space for the dark matter mass ranging from 5 GeV to 10 TeV.