T. Caldwell

First dark matter search results from a surface run of the 10-L DMTPC directional dark matter detector

Abstract The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Torr CF4) 10 liter detector capable of measuring the vector direction of nuclear recoils with the goal of directional dark matter detection. In this Letter we present the first dark matter limit from DMTPC from a surface run at MIT. In an analysis window of 80–200 keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper limit on the spin-dependent WIMP-proton cross section of 2.0 × 10 − 33 cm 2 for 115 GeV/c2 dark matter particle mass.

Results from DMTPC 10-liter detector

The known direction of motion of dark matter particles relative to the Earth may be a key for their unambiguous identification even in the presence of backgrounds. A direction-sensitive detector prototype using a low-density CF4 gas with a 10 liter fiducial volume is operated for several weeks in a basement laboratory. We present initial results that confirm good detector performance and set preliminary limits on spin-dependent dark matter interactions.

DMTPC: A dark matter detector with directional sensitivity

By correlating nuclear recoil directions with the Earth’s direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence of backgrounds. Here, we describe the Dark Matter Time‐Projection Chamber (DMTPC) detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this detector, we have measured the vector direction (head‐tail) of nuclear recoils down to energies of 100 keV with an angular resolution of ≤15°. To study our detector backgrounds, we have operated in a basement laboratory on the MIT campus for several months. We are currently building a new, high‐radiopurity detector for deployment underground at the Waste Isolation Pilot Plant facility in New Mexico.

The DMTPC detector

Directional Dark Matter detectors have the potential of yielding an unambiguous observation of WIMPs even in presence of insidious background. In addition, by measuring the direction of the Dark Matter particles such detectors can discriminate between the various models that describe Dark Matter in our galaxy. The DMTPC detector is a novel directional DM detector consisting of a low-pressure CF4 time projection chamber with optical readout. Recent measurements proved that this technology is able to reconstruct the energy, direction, and sense of the lowenergy nuclear recoils produced by neutrons from a 252Cf source, as well as efficiently reject electromagnetic backgrounds. A 10-liter DMTPC detector is ready for underground operation. A 1 m3 detector, now in the design phase, will soon allow us to improve the existing limits of SD-interactions of WIMPs on protons by over one order of magnitude.