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Constraints on inelastic dark matter from XENON10

J. Angle, E. Aprile, F. Arneodo, L. Baudis, A. Bernstein, A. Bolozdynya, P. Brusov, L. C. C. Coelho, C. E. Dahl, L. DeViveiros, A. D. Ferella, L. M. P. Fernandes, S. Fiorucci, R. J. Gaitskell, K. L. Giboni, R. Gomez, R. Hasty, L. Kastens, J. Kwong, J. A. M. Lopes, N. Madden, A. Manalaysay, A. Manzur, D. N. McKinsey, M. E. Monzani, K. Ni, U. Oberlack, J. Orboeck, G. Plante, R. Santorelli, J. M. F. dos Santos, P. Shagin, T. Shutt, P. Sorensen, S. Schulte, C. Winant, M. Yamashita

TL;DR

This study tests inelastic dark matter (iDM) as a reconciliation of the DAMA modulation with null results by reanalyzing XENON10 data up to $E_{nr}=75$ keV. It derives the iDM signal rate with a Helm form factor and Maxwellian halo, and implements a detailed background treatment using Poisson leakage and pulse-shape discrimination to extract a robust nuclear-recoil sample. The resulting 90% CL exclusions disfavor $m_χ \gtrsim 150$ GeV for certain $L_{eff}$ choices, with lighter masses leaving some overlap with the DAMA-allowed region depending on δ and the escape velocity; the work also yields a model-independent constraint on the DAMA modulation fraction. Overall, the paper highlights the importance of high-energy recoil sensitivity and passive-background control in testing iDM scenarios and provides strengthened limits that challenge iDM as a DAMA explanation under the studied assumptions.

Abstract

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E$_{nr}=75$ keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses $m_χ\gtrsim150$ GeV are disfavored.

Constraints on inelastic dark matter from XENON10

TL;DR

This study tests inelastic dark matter (iDM) as a reconciliation of the DAMA modulation with null results by reanalyzing XENON10 data up to keV. It derives the iDM signal rate with a Helm form factor and Maxwellian halo, and implements a detailed background treatment using Poisson leakage and pulse-shape discrimination to extract a robust nuclear-recoil sample. The resulting 90% CL exclusions disfavor GeV for certain choices, with lighter masses leaving some overlap with the DAMA-allowed region depending on δ and the escape velocity; the work also yields a model-independent constraint on the DAMA modulation fraction. Overall, the paper highlights the importance of high-energy recoil sensitivity and passive-background control in testing iDM scenarios and provides strengthened limits that challenge iDM as a DAMA explanation under the studied assumptions.

Abstract

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses GeV are disfavored.

Paper Structure

This paper contains 10 sections, 3 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. The XENON10 detector
  3. Inelastic dark matter
  4. Predicted Event Rates
  5. Event acceptance
  6. Poisson likelihood
  7. Primary scintillation pulse shape
  8. Electromagnetic Backgrounds
  9. dark matter exclusion limits
  10. Summary

Figures (4)

  • Figure 1: (color online) Events remaining after re-analysis of 58.6 live days of dark matter search data. The dark matter acceptance box is bounded by the stair-step lines indicating the centroid and $-3\sigma$ bounds obtained from fits to the neutron calibration data. The fitted electron recoil centroid is shown as a solid blue curve, and the $-3\sigma$ contour is shown dashed. The 13 events remaining in the acceptance box are circled. An $S2$ software threshold of 12 electrons was imposed in the analysis.
  • Figure 2: (color online) (top) The distribution of $f_{p}$ for electron recoil calibration data. The black dashed line indicates the discrimination cut bound on this parameter. (bottom) The distribution of $f_{p}$ for nuclear recoil calibration data. The acceptance $\epsilon_f$ of the cut is listed in Table \ref{['table1']}.
  • Figure 3: (color online) The fraction of leakage events remaining among single gamma ray scatters in the electron recoil calibration data set (black stars). Also shown are the Monte Carlo prediction for false single scatters, with an additional scatter below the cathode grid (red triangles), or in the outer 8.7 kg of xenon (blue circles). The sum of the two Monte Carlo components is indicated by pink squares. Note that the $x$ axis is electron (not nuclear) recoil equivalent energy; 20 keVee = 76 keVr.
  • Figure 4: (color online) The solid black curves indicates the 90% C.L. exclusion limits obtained from XENON10 data, with $\mathcal{L}_{eff}$ given by 2009aprile2009sorensen (solid gray curves take $\mathcal{L}_{eff}$ from 2009manzur). The filled regions indicate the 90% (magenta, darker) and 99% (cyan, lighter) C.L. DAMA-allowed regions.