Exploring the dark matter inelastic frontier with 79.6 days of PandaX-II data

Xun Chen et al. (PandaX-II Collaboration)

Phys. Rev. D 96, 102007 – Published 28 November 2017

Abstract

We report here the results of searching for inelastic scattering of dark matter (initial and final state dark matter particles differ by a small mass splitting) with a nucleon for the first 79.6 days of PandaX-II data (Run 9). We set the upper limits for the spin independent weakly interactive massive particle–nucleon scattering cross section up to a mass splitting of $300 keV / c^{2}$ at two benchmark dark matter masses of 1 and $10 TeV / c^{2}$ .

Received 21 August 2017

DOI:https://doi.org/10.1103/PhysRevD.96.102007

Physics Subject Headings (PhySH)

Particle dark matter

Weakly interacting massive particles

Dark matter detectors

Particles & Fields

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Vol. 96, Iss. 10 — 15 November 2017

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Images

Figure 1
The expected event rate for scattering between WIMPs and Xe nuclei at the WIMP masses of $1 TeV / c^{2}$ (top) and $10 TeV / c^{2}$ (bottom), respectively, and the mass splitting values of 0, 100, 200, $300 keV / c^{2}$ . The SI WIMP-nucleon cross section $σ_{n}$ is fixed at $10^{- 40} {cm}^{2}$ . The rate is given in the unit of ${keV}^{- 1} {kg}^{- 1} {day}^{- 1}$ (DRU). (a) WIMP mass is $1 TeV / c^{2}$ ; (b) WIMP mass is $10 TeV / c^{2}$ .
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Figure 2
The detection efficiency of PandaX-II experiment as a function of the nuclear recoil energy. The dark blue curve represents the selection efficiency of data quality cuts (see Ref. [15]). The red dashed line is obtained with an additional $S 1$ range cut of (3, 45) photoelectron (PE) and an upper range of 10,000 PE for $S 2$ . The blue solid line is obtained with an extended $S 1$ and $S 2$ window: $S 1$ within (3, 100) PE, and S2 less than 12,000 PE.
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Figure 3
The expected signal distribution of WIMP-nucleon scattering at the WIMP mass of $m_{χ} = 1 TeV / c^{2}$ and the mass splitting $δ$ values of 0, 100, 200, and $300 keV / c^{2}$ , with one set of PandaX-II detector condition parameters. The SI WIMP-nucleon cross section $σ_{n}$ is fixed at $10^{- 40} {cm}^{2}$ . The total expected event rates at each mass splitting are 5.16, 0.21, $5.23 \times 10^{- 4}$ and $3.18 \times 10^{- 7} evt / kg / day$ , respectively. The 35% quantile of the nuclear recoil (NR) band from AmBe calibration (red dashed line) is overlaid in each plot.
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Figure 4
Spatial distribution of events before the FV cut with expanded signal window (gray points), and those of events below the reference acceptance line (outside FV: red points; inside FV: blue triangles). The FV cuts are indicated by the black dashed lines.
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Figure 5
The $\log_{10} (S 2 / S 1)$ vs $S 1$ distribution of selected events within the expanded signal window. A reference acceptance line is indicated as the red dashed line, below which four events (blue triangles) are identified.
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Figure 6
The 90% C.L. upper limits (red solid line) for the SI WIMP-nucleon cross section $σ_{n}$ from the PandaX-II run 9 data with expanded signal window at two reference dark matter masses of $1 TeV / c^{2}$ (top) and $10 TeV / c^{2}$ (bottom). The 1 and $2 − σ$ sensitivity bands are shown in green and yellow, respectively, and the medians of the sensitivity band are given in a black dashed line. The red dotted line gives the upper limits calculated with the original data selection window. Upper limits calculated with a tuned NEST model by LUX are indicated by the blue solid line. The blue squares indicate the possible WIMP mass splittings and nucleon scattering cross sections by the CRESST data [9]. (a) WIMP mass is $1 TeV / c^{2}$ ; (b) WIMP mass is $10 TeV / c^{2}$ .
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