February 14, 2008
Dark Matter COUPP
by Juan Collar

The Chicagoland Observatory for Underground Particle Physics (COUPP) announced new constraints on dark matter particles known as WIMPs in the February 15 issue of the journal Science. These first results from COUPP improve limits on ''spin-dependent'' WIMP interactions, and rule out the last remaining dark matter models in which such interactions could be responsible for the claimed WIMP detections by the DArk MAtter (DAMA) experiment in Italy. COUPP began taking data in 2005, using a bubble chamber detector located 350 meters underground in the MINOS gallery at Fermilab. KICP professor Juan Collar is spokesman for the collaboration, which presently includes 16 scientists and students from the University of Chicago, Fermi National Accelerator Laboratory, and Indiana University, South Bend. Image: KICP fellow Brian Odom next to the inner vessel of a 20 kg COUPP bubble chamber under construction.

In direct detection experiments in which an incoming WIMP bounces off of a nucleus in the detector, a WIMP can be characterized by its mass, its spin-independent couplings and its spin-dependent couplings. COUPP utilizes a superheated heavy liquid (CF₃I) which is maximally sensitive to both spin-dependent and spin-independent interactions simultaneously. The current setup consists of a 2 kg prototype chamber, which is expected to produce improved limits on both couplings during 2008. A 20 kg chamber and 80 kg chamber are presently under construction.

KICP COUPP members include Professor Juan Collar, KICP fellows Brian Odom and Andrew Sonnenschein; graduate students Dante Nakazawa and Matthew Szydagis; and undergraduate students William Bolte, Jason Hall, Kevin O'Sullivan, Aaron Plasek, Smriti Mishra, Julia Rasmussen, Aza Raskin, Hannes Schimmelpfennig, and Luke Goetzke. Image: KICP graduate student Matthew Szydagis is standing in front of a camera array for a ''windowless'' COUPP bubble chamber, a new concept.

COUPP article: Spin-Dependent WIMP Limits from a Bubble Chamber, E. Behnke, J. I. Collar, P. S. Cooper, K. Crum, M. Crisler, M. Hu, I. Levine, D. Nakazawa, H. Nguyen, B. Odom, E. Ramberg, J. Rasmussen, N. Riley, A. Sonnenschein, M. Szydagis, R. Tschirhart , Science 15 February 2008, Vol. 319. no. 5865, pp. 933 - 936

Fermilab Press Release
COUPP Fermilab

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KICP Members: Juan I. Collar; Brian C. Odom; Andrew Sonnenschein
KICP Students: William "Joe" Bolte; Luke Goetzke; Jason Hall; Smriti Mishra; Dante Nakazawa; Kevin O'Sullivan; Aza Raskin; Julia Rasmussen; Hannes Schimmelpfennig; Matthew Szydagis
Scientific projects: Chicagoland Observatory for Underground Particle Physics (COUPP)