Spin-Dependent Weakly-Interacting-Massive-Particle–Nucleon Cross Section Limits from First Data of PandaX-II Experiment

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]

Terrestrial and martian heat flow limits on dark matter

“…Again simulating many DM capture events as described in Section 4.1, but now also using the self-annihilation cross section to determine the total heating rate as described above, we determined values of m χ , σ χχ , and σ χN corresponding to a C χ that yielded a heat flux of ∼44 TW. By running simulations with multiple combinations of these three parameters, we found exclusion limits for values of σ χχ , shown as dashed lines in Figures 3,4,5,6,7,8,9,and 10. Note that for a sufficiently large DM-DM s-wave annihilation cross section, the white partial annihilation lines converge on the total annihilation limit, at σ χχ 10 −35 cm 2 for Earth and σ χχ 10 −34 cm 2 for Mars.…”

Low-mass dark matter search with CDMSlite

“…For both, the median (90% C.L.) (thick black solid curve) upper limit from CDMSlite Run 2 is compared to other selected direct-detection limits from PANDAX-II (thick-green dotted curve) [61], LUX (thick-green dotdashed curve) [62], XENON100 (thick-green dashed curve) [63], PICO-60 (magenta upward triangles) [64], PICO-2L (magenta downward triangles) [65], PICASSO (purple dot-dashed band) [66], CDEX-0 (thin-red dashed curve) [67,68], and CDEX-1 (thin-red solid curve) [68]. The orange band surrounding the Run 2 result is the 95% uncertainty interval on the upper limit.…”

Limits on Spin-Dependent WIMP-Nucleon Cross Section Obtained from the Complete LUX Exposure

“…Solid gray curves show the previously published LUX WS2013 limits [13]. Constraints from other LXe TPC experiments are also shown, including XENON100 [26] and PandaX-II [27]. In the top panel, model-dependent (axial-vector mediator with indicated couplings) LHC search results are represented by dashed lines, with CMS [28] in light blue, and ATLAS [29] in dark blue.…”