CDMS-II Data Release Phase I for the Low Threshold Modulation Analysis

September 18, 2012

Table of Contents

1. Description of data release phase I
2. Data verification
3. References

Description of Data Release Package, Phase I

The data for phase I of the data release for the CDMS-II low threshold analysis/search for annual modulation was extracted from CDMS-II data from 2006-2008.

The release includes:

• Ionization and Nuclear Recoil energies
  • All Q-inner Singles (after data quality cuts) with phonon nuclear-recoil-equivalent energies in the range 2-20 keVnr
  • All Q-inner Multiples (after data quality cuts) with phonon nuclear-recoil-equivalent energies in the range 2-20 keVnr
  • Corresponding ionization energies of released events
• Data Quality efficiencies
  • Trigger efficiencies vs keVnr, for each detector
  • Data Quality efficiencies vs keVnr, for each detector
  • Total livetime, for each detector
• Event bands
  • Nuclear recoil (NR) band, polynomial fits to upper and lower band edges (for each detector)
  • Electron recoil (ER) band, polynomial fits to upper and lower band edges (for each detector)
  • Zero charge (ZC) band mean and sigma, for each detector (energy independent; assumes Gaussian spread to band)
• Plotting routine for the CDMS low energy data release (in MATLAB) (additional details below)
• Text file containing the event counts for each NR, ER, and ZC band ("Event_Numbers.txt")

The ER, NR, and ZC bands provided for each detector in this release are based on the livetime-weighted averages of the run-by-run bands used in the CDMS-II low threshold PRL (10.1103/PhysRevLett.106.131302). The +/- 2-sigma bands for each detector have been fit with third-order polynomials, and the coefficients to these fits are provided as part the data release. The definitions of the ER and NR run-by-run bands are described in section 4.5 of the thesis of D. Moore (D. Moore 2012). The energy-independent zero charge band approximation, which also assumes a Gaussian spread in ionization energy, is discussed briefly on pages 129- 130 of that thesis. In this distribution, the ZC band is simply assumed to be all events lying within +/-2-sigma of the mean of the baseline noise distribution.

Data Verification

In addition to the data described above, the release also includes a file for verifying the number of events in each band ("Event_Numbers.txt") and a MATLAB-based plotting routine to reproduce the following plots for the end user. Figure 1 shows the 2-dimensional histogram for the nuclear recoil and ionization distributions of the single-scatter events for all eight low threshold detectors, while Figure 2 shows the same distributions for the multiple-scatter events. Visible in thse plots are the events in the electron recoil band, the nuclear recoil band, and the zero charge band; the latter strongly overlaps with the NR band and contributes significantly to the background in low threshold analyses.

Figure 1: Singles Distribution, all detectors	Figure 2: Multiples Distribution, all detectors

Figure 3 shows the data quality and trigger efficiencies for each of the eight detectors as a function of energy. In particular, it highlights the threshold and the rise in efficiency at low keVnr due to relaxation of the cuts at low energies.	Figure 3. Data quality and trigger efficiencies vs. energy, by detector

References

1. J.P. Filippini, A Search for WIMP Dark Matter Using the First Five-Tower Run of the Cryogenic Dark Matter Search, Ph.D. Thesis, Department of Physics, University of California, Berkeley (2008). pdf.
2. D. Moore, A Search for Low-Mass Dark Matter with the Cryogenic Dark Matter Search and the Development of Highly Multiplexed Phonon-Mediated Particle Detectors, Ph.D. Thesis, Division of Physics, Mathematics & Astronomy, California Institute of Technology (2012). pdf.
3. S. A. Hertel, Advancing Dark Matter Direct Detection from CDMS-II to SuperCDMS, Ph.D. Thesis, Department of Physics, Massachusetts Institute of Technology (2012).
4. (CDMS Collaboration) Results from a Low-Energy Analysis of the CDMS-II Germanium Data, Phys. Rev. Lett. 106, 131302 (2011), arxiv.org/abs/1011.2482v3.
5. (CDMS Collaboration) Search for annual modulation in low-energy CDMS-II data, arXiv:1203.1309v1 [astro-ph.CO].