Phys. Rev. D 103, 063028 (2021) - Search for inelastic scattering of WIMP dark matter in XENON1T

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Search for inelastic scattering of WIMP dark matter in XENON1T

E. Aprile et al. (XENON Collaboration)

Phys. Rev. D 103, 063028 – Published 19 March 2021

Abstract

We report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off ${}^{129}{Xe}$ is the most sensitive probe of inelastic WIMP interactions, with a signature of a 39.6 keV deexcitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.83 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than $2 σ$ . A profile-likelihood ratio analysis is used to set upper limits on the cross section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than $100 GeV / c^{2}$ , with the strongest upper limit of $3.3 \times 10^{- 39} {cm}^{2}$ for $130 GeV / c^{2}$ WIMPs at 90% confidence level.

Received 20 November 2020
Accepted 23 February 2021

DOI:https://doi.org/10.1103/PhysRevD.103.063028

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Dark matter Particle dark matter

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Vol. 103, Iss. 6 — 15 March 2021

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Figure 1
Model for inelastic scattering of neutrons (pink $1 σ$ , $2 σ$ , and $3 σ$ contours) compared to calibration data with the neutron generator deployed. The density of calibration data is represented by the shading inside the $2 σ$ contour, while outside individual events in the calibration data are shown as green dots. The white unshaded region indicates the region in which the fit is performed. Energy contours are shown as gray lines.
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Figure 2
Region of interest showing the four nominal background models: ${}^{214}{Pb}$ in gray, ${}^{83 m}{Kr}$ in green, ${}^{124}{Xe}$ in pink, and ${}^{125}I$ in blue; and the expected signal for a $100 GeV / c^{2}$ WIMP in red. In each case, the darker and lighter shading show the $1 σ$ and $2 σ$ region, respectively. The $cS 2_{b} / cS 1$ distribution for ${}^{214}{Pb}$ is used to visualize the $2 ν ECEC − KK$ and EC-K peaks, which are only modeled in energy. The dotted lines indicate the boundaries of the bins used to perform the likelihood fit.
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Figure 3
Observed events in the 0.83 t exposure, shown as error bars. Between 29 and 55 keV, the six histograms correspond to the six $cS 2_{b} / cS 1$ bins as shown in Fig. 2. Above 55 keV only, a single $cS 2_{b} / cS 1$ bin is shown, as used for the analysis. The single bin from 15 to 29 keV is not shown, since it is instead used to constrain the background rate in the rest of the analysis region. The shaded areas show the estimated background in each bin from ${}^{214}{Pb}$ (gray), ${}^{83 m}{Kr}$ (green), ${}^{124}{Xe}$ (pink), and ${}^{125}I$ (blue), based on a background-only best fit to the science data. The solid (dotted) red line shows the signal expected from a $50 GeV / c^{2}$ ( $100 GeV / c^{2}$ ) WIMP scattering inelastically, with a cross section of $10^{- 37} {cm}^{2}$ , on top of the background estimation. The inset shows a more abstract representation of the same data (from the full region of interest). Analysis bins are ordered according to the ratio between the expected number of signal events from a $50 GeV / c^{2}$ WIMP and the expected number of background events and then grouped into the six shown here. An upwards fluctuation is present in the right-hand bins, explaining the origin of the upwards fluctuation of the limit within the expected band.
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Figure 4
Upper limit, at 90% CL, on the cross section for inelastic scattering of WIMPs off xenon nuclei. The expected range at $1 σ$ and $2 σ$ is shown in green and yellow, respectively. Our result is compared to upper limits obtained by the XMASS Collaboration [47] (blue dot-dashed line) and XENON100 [48] (orange dashed line).
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Physical Review D

covering particles, fields, gravitation, and cosmology

Search for inelastic scattering of WIMP dark matter in XENON1T

E. Aprile et al. (XENON Collaboration)

Phys. Rev. D 103, 063028 – Published 19 March 2021

Abstract

Physics Subject Headings (PhySH)

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Article Text

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Issue

Physical Review D

covering particles, fields, gravitation, and cosmology

Search for inelastic scattering of WIMP dark matter in XENON1T

E. Aprile et al. (XENON Collaboration)

Phys. Rev. D 103, 063028 – Published 19 March 2021

Abstract

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