Spin-Dependent WIMP Limits from a Bubble Chamber
E. Behnke,1
J. I. Collar,2*
P. S. Cooper,3
K. Crum,2
M. Crisler,3
M. Hu,3
I. Levine,1
D. Nakazawa,2
H. Nguyen,3
B. Odom,2
E. Ramberg,3
J. Rasmussen,2
N. Riley,2
A. Sonnenschein,3
M. Szydagis,2
R. Tschirhart3
Bubble chambers were the dominant technology used for particle
detection in accelerator experiments for several decades, eventually
falling into disuse with the advent of other techniques. We
report here on a new application for these devices. We operated
an ultraclean, room-temperature bubble chamber containing 1.5
kilograms of superheated CF
3I, a target maximally sensitive
to spin-dependent and -independent weakly interacting massive
particle (WIMP) couplings. An extreme intrinsic insensitivity
to the backgrounds that commonly limit direct searches for dark
matter was measured in this device under operating conditions
leading to the detection of low-energy nuclear recoils like
those expected from WIMPs. Improved limits on the spin-dependent
WIMP-proton scattering cross section were extracted during our
experiments, excluding this type of coupling as a possible explanation
for a recent claim of particle dark-matter detection.
2 Department of Physics, Enrico Fermi Institute, and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA.
3 Fermi National Accelerator Laboratory, Batavia, IL 60510, USA.
* To whom correspondence should be addressed. E-mail: collar{at}uchicago.edu
