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Relative Measurement and Extrapolation of the Scintillation Quenching Factor of $α$-Particles in Liquid Argon using DEAP-3600 Data

DEAP Collaboration, P. Adhikari, M. Alpízar-Venegas, P. -A. Amaudruz, J. Anstey, D. J. Auty, M. Batygov, B. Beltran, C. E. Bina, W. Bonivento, M. G. Boulay, J. F. Bueno, B. Cai, M. Cárdenas-Montes, S. Choudhary, B. T. Cleveland, R. Crampton, S. Daugherty, P. DelGobbo, P. Di Stefano, G. Dolganov, L. Doria, F. A. Duncan, M. Dunford, E. Ellingwood, A. Erlandson, S. S. Farahani, N. Fatemighomi, G. Fiorillo, R. J. Ford, D. Gahan, D. Gallacher, P. García Abia, S. Garg, P. Giampa, A. Giménez-Alcázar, D. Goeldi, P. Gorel, K. Graham, A. L. Hallin, M. Hamstra, S. Haskins, J. Hu, J. Hucker, T. Hugues, A. Ilyasov, B. Jigmeddorj, C. J. Jillings, G. Kaur, M. Khoshraftar Yazdi, A. Kemp, M. Kuźniak, F. La Zia, M. Lai, S. Langrock, B. Lehnert, N. Levashko, M. Lissia, L. Luzzi, I. Machulin, A. Maru, J. Mason, A. B. McDonald, T. McElroy, J. B. McLaughlin, C. Mielnichuk, L. Mirasola, A. Moharana, J. Monroe, A. Murray, C. Ng, G. Oliviéro, M. Olszewski, S. Pal, D. Papi, B. Park, M. Perry, V. Pesudo, T. R. Pollmann, F. Rad, C. Rethmeier, F. Retière, L. Roszkowski, R. Santorelli, F. G. Schuckman, S. Seth, V. Shalamova, P. Skensved, T. Smirnova, K. Sobotkiewich, T. Sonley, J. Sosiak, J. Soukup, R. Stainforth, M. Stringer, J. Tang, E. Vázquez-Jáuregui, S. Viel, B. Vyas, M. Walczak, J. Walding, M. Ward, S. Westerdale, R. Wormington

TL;DR

This work addresses the need for accurate alpha scintillation quenching in liquid argon to model alpha-induced backgrounds in LAr-based dark matter detectors. It employs a relative measurement of the alpha QF in the MeV region using the $^{222}$Rn decay chain in the DEAP-3600 detector, and combines this with a Birks-like electronic quenching model and TRIM-based nuclear quenching to extrapolate to low energies. The study yields an energy-dependent $QF_{\alpha}(E)$ curve from $\sim$10 keV to 10 MeV, with quantified uncertainties, and finds that electronic quenching dominates at high energy while nuclear quenching becomes significant at low energy. The resulting QF curve improves background predictions for DEAP-3600 and informs future analyses of alpha backgrounds in liquid-argon dark matter experiments.

Abstract

The knowledge of scintillation quenching of $α$-particles plays a paramount role in understanding $α$-induced backgrounds and improving the sensitivity of liquid argon-based direct detection of dark matter experiments. We performed a relative measurement of scintillation quenching in the MeV energy region using radioactive isotopes ($^{222}$Rn, $^{218}$Po and $^{214}$Po isotopes) present in trace amounts in the DEAP-3600 detector and quantified the uncertainty of extrapolating the quenching factor to the low-energy region.

Relative Measurement and Extrapolation of the Scintillation Quenching Factor of $α$-Particles in Liquid Argon using DEAP-3600 Data

TL;DR

This work addresses the need for accurate alpha scintillation quenching in liquid argon to model alpha-induced backgrounds in LAr-based dark matter detectors. It employs a relative measurement of the alpha QF in the MeV region using the Rn decay chain in the DEAP-3600 detector, and combines this with a Birks-like electronic quenching model and TRIM-based nuclear quenching to extrapolate to low energies. The study yields an energy-dependent curve from 10 keV to 10 MeV, with quantified uncertainties, and finds that electronic quenching dominates at high energy while nuclear quenching becomes significant at low energy. The resulting QF curve improves background predictions for DEAP-3600 and informs future analyses of alpha backgrounds in liquid-argon dark matter experiments.

Abstract

The knowledge of scintillation quenching of -particles plays a paramount role in understanding -induced backgrounds and improving the sensitivity of liquid argon-based direct detection of dark matter experiments. We performed a relative measurement of scintillation quenching in the MeV energy region using radioactive isotopes (Rn, Po and Po isotopes) present in trace amounts in the DEAP-3600 detector and quantified the uncertainty of extrapolating the quenching factor to the low-energy region.

Paper Structure

This paper contains 10 sections, 12 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Detector and data selection
  3. Relative measurement of the quenching factor
  4. Method
  5. Systematic uncertainties
  6. Extrapolation of the quenching factor
  7. Nuclear quenching factor
  8. Electronic quenching factor
  9. Combined results
  10. Summary and outlook

Figures (6)

  • Figure 1: Distribution of the number of PE detected from $\alpha$-decay events the position of which is reconstructed within radius 0--850 mm (top histogram) and 0--600 mm (bottom histogram) from the origin of the detector. From left to right, the peaks are from the decay of the $^{210}$Po, $^{222}$Rn, $^{218}$Po and $^{214}$Po isotopes. Each peak is fitted by a Gaussian distribution (blue line). Red solid points are the detected peak PE positions from each Gaussian fit.
  • Figure 2: Nuclear QF curve for $\alpha$-particles estimated using SRIM stopping power tables and Eq. \ref{['eq:Lind-styleEq']} (green) and TRIM simulation (black).
  • Figure 3: Stopping power curves for $\alpha$-particles in LAr from SRIM-2013 Ziegler1985.
  • Figure 4: $\chi^{2}$ from Eq. \ref{['Eq:chi2_eq']} shown as a function of $A$ and $B$. The red-dotted line represents the 1$\sigma$ contour drawn in the $(A,B)$ parameter space.
  • Figure 5: Electronic QF as a function of $\alpha$-particle energy. The best-fit QF curve is shown with the red dashed line. The green shaded region is the 1$\sigma$ band considering only the uncertainties of the relative measurement, as a function of energy. This band encompasses the absolute uncertainty from the measurement of ${\rm QF}_{\alpha, \rm ^{210}Po}$ which is the dominant uncertainty in this analysis. The red solid square represents T. Doke's measurement of the scintillation quenching of $\alpha$-particles emitted from the decay of $^{210}$Po DOKE1988291. Two black open circles display the DEAP-3600 relative measurements from $^{218}$Po and $^{214}$Po (see Table \ref{['tab:QF_table']}).
  • ...and 1 more figures