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Final Analysis and Results of the Phase II SIMPLE Dark Matter Search

M. Felizardo, T. A. Girard, T. Morlat, A. C. Fernandes, A. R. Ramos, J. G. Marques, M. Auguste, D. Boyer, A. Cavaillou, J. Poupeney, C. Sudre, J. Puibasset, H. S. Miley, R. F. Payne, F. P. Carvalho, M. I. Prudêncio, R. Marques

TL;DR

The final results of the Phase II SIMPLE measurements are reported, comprising two run stages of 15 superheated droplet detectors each, with the second stage including an improved neutron shielding and revised nucleation efficiency based on a reanalysis of previously reported monochromatic neutron irradiations.

Abstract

We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, the second stage including an improved neutron shielding. The analyses includes a refined signal analysis, and revised nucleation efficiency based on reanalysis of previously-reported monochromatic neutron irradiations. The combined results yield a contour minimum of σ_{p} = 4.2 x 10^-3 pb at 35 GeV/c^2 on the spin-dependent sector of WIMP-proton interactions, the most restrictive to date from a direct search experiment and overlapping for the first time results previously obtained only indirectly. In the spin-independent sector, a minimum of 3.6 x 10^-6 pb at 35 GeV/c^2 is achieved, with the exclusion contour challenging the recent CoGeNT region of current interest.

Final Analysis and Results of the Phase II SIMPLE Dark Matter Search

TL;DR

The final results of the Phase II SIMPLE measurements are reported, comprising two run stages of 15 superheated droplet detectors each, with the second stage including an improved neutron shielding and revised nucleation efficiency based on a reanalysis of previously reported monochromatic neutron irradiations.

Abstract

We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, the second stage including an improved neutron shielding. The analyses includes a refined signal analysis, and revised nucleation efficiency based on reanalysis of previously-reported monochromatic neutron irradiations. The combined results yield a contour minimum of σ_{p} = 4.2 x 10^-3 pb at 35 GeV/c^2 on the spin-dependent sector of WIMP-proton interactions, the most restrictive to date from a direct search experiment and overlapping for the first time results previously obtained only indirectly. In the spin-independent sector, a minimum of 3.6 x 10^-6 pb at 35 GeV/c^2 is achieved, with the exclusion contour challenging the recent CoGeNT region of current interest.

Paper Structure

This paper contains 4 figures.

Figures (4)

  • Figure 1: scatter plot of the amplitudes and frequency of the primary harmonic of each true nucleation event observed over the Stage 2 exposure, with the boxed event for pressures $\leq$ 2.2 bar.
  • Figure 2: variation of the recoil and $\alpha$ energy thresholds with temperature for the three C$_{2}$ClF$_{5}$ constituents at 2.00 (solid), 2.50 (dash) and 3.00 (dash-dot) bar, with $\Lambda$=1.40. The freon constituents are identified for 2.5 bar. The vertical line indicates the 9$^{\circ}$C measurement temperature; the horizontal line, a threshold recoil energy of 8 keV.
  • Figure 3: various spin-dependent WIMP-proton exclusion contours for Phase II, together with the leading direct picassotaupcoupptaupkimstaup and indirect SuperK desai, IceCube abbasi search results; shown are the Stage 2 result, the reanalyzed Stage 1 result, and a merging of the two. The region outlined in grey is favored by cMSSM roszkowski.
  • Figure 4: various spin-independent contours for Phase II, together with those of the leading xenon2008xenon2011xenon2011acdms2010cdms2011coupptaupkimstauppicasso2012zeplin2009zeplin2010 spin-independent search results; shown are the Stage 2 result, the reanalyzed Stage 1 result, and a merging of the two. The partial contours (a) and (b) are taken from cdms2011 and xenon2011, respectively. The closed areas identified as either CRESST-II cresst2, DAMA/LIBRA dama or CoGeNT cogent2011 represent the regions in which possible light mass WIMPS have been respectively reported.