Maximum Likelihood Analysis of Low Energy CDMS II Germanium Data

Abstract

We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search (CDMS~II) experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from ${}^{210}$Pb decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in our data. We confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.

arXiv comment12 pages, 12 figures, submitted to PRD

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• Dark matter effective field theory scattering in direct detection experiments
• Annual Modulation in Direct Dark Matter Searches
• G4CMP: Condensed Matter Physics Simulation Using the Geant4 Toolkit
• Extended Maximum Likelihood Halo-independent Analysis of Dark Matter Direct Detection Data
• Production Rate Measurement of Tritium and Other Cosmogenic Isotopes in Germanium with CDMSlite
• SAGE : A Monte Carlo Simulation Framework for Experiments with Germanium Detectors