Characterization of a Cryogenic Detector to Improve Background Rejection

Peter Hyland with Dan Akerib

Characterization of a Cryogenic Detector to Improve Background Rejection

Based on our understanding of gravity, observations of the motion of stars and galaxies demonstrate a stronger gravitational force than can be accounted for by observable matter, i.e. matter that emits or absorbs light.  Big Bang Nucleosynthesis suggests that the average density of baryonic matter, in units of critical density, is 0.05 ± 0.01.  However, the total mass density, in units of critical density, WM, is 0.4 ± 0.1.  Therefore another form of matter must be responsible for this “extra” gravity.  One hypothetical type of dark matter, so called because it neither absorbs nor emits light, is a Weakly Interacting Massive Particle (WIMP).  There are many different forms that a WIMP could take but particle physics provides specific candidates from Supersymmetry.  These candidate particles have a mass range of 50 – 500 GeV and weak interaction cross sections.

    CWRU is a member of the Cryogenic Dark Matter Search (CDMS), a collaboration of several institutions, which uses low temperature particle detectors that are sensitive to WIMPs and provide good background rejection.  Since these detectors, which use novel technology, will soon be installed in the low-background experimental site, they have not been extensively operated under experimental conditions.  It is known that the detectors have good sensitivity, but they have not been fully characterized.  Over the next year, this senior project will characterize the response of a detector, guided by the needs at the experimental site to improve background rejection.  Signals from photon, electron, and neutron sources are likely to be background signals and we will expose a detector to artificial sources of these particles.

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