18-20 May 2015, Underground Science Conference, SDSM&T 1John Harton, Colorado State University Recent Results from the DRIFT Directional DM Experiment John Harton, Department of Physics, Colorado State University

18-20 May 2015, Underground Science Conference, SDSM&T 2John Harton, Colorado State University Seasonal, due to velocity of Earth about the Sun. Order ±2% effect in overall event rate, higher in June, lower in December. Domain of dense-target experiments, which comprise most of the field of DM experimental research. Yearly DM Event Rate Modulation DAMA NaI + PMTs Direction to Cygnus

18-20 May 2015, Underground Science Conference, SDSM&T 3John Harton, Colorado State University Sidereal DM Directional Modulation At noon, say, WIMPS enter generally from top of detector Half a sidereal day later (11 h 58 m) the WIMPs enter the end of the detector Domain of low-pressure gas detectors, mostly keV Recoil energy for 1000 GeV WIMP mass Recoil directions Matt Williams, CSU As for the DRIFT detector Sidereal signal goes out of phase with day/night and seasons. Challenge is event rate.

18-20 May 2015, Underground Science Conference, SDSM&T 4John Harton, Colorado State University Techniques to detect WIMP DM Neutrons give signals like WIMPS would. Gammas give a less dense ionization track. NUCLEUS Nucleus leaves its energy in form of: CHARGE - ions HEAT – phonons or vibrations LIGHT - scintillation Kinetic energy of few to few * 100 keV …low energy. Stops quickly. This distance is very short for a dense detector, And mm for low density gas. At its most simple: hard-sphere scattering WIMP

18-20 May 2015, Underground Science Conference, SDSM&T 5John Harton, Colorado State University DRIFT Directional DM Exp’t Basics Central cathode at HHV provides drift field 40 torr pressure (CS 2 ) - ion drift. Challenges: Eliminate bckgnds, Rn is tough Fiducialize in drift direction Measure extended tracks Measure starting and ending points of track WIMP-induced nuclear recoils will be order mm in length in 40 torr 1 m 3

18-20 May 2015, Underground Science Conference, SDSM&T 6John Harton, Colorado State University 1 m 3 nominal volume 0.8 m 3 fiducial volume CS 2 + CF 4 +O 2 gas, torr CS 2 for negative ion drift CF 4 provides spin- dependent WIMP target. O 2 provides minority carriers  fiducialization DRIFT Directional DM Exp’t DRIFT is in the Boulby mine, England. Current Collaboration: Occidental College, Univ. New Mexico, Colorado State Univ., Univ. Hawaii and Wellesley, and in UK Sheffield and Edinburgh.

18-20 May 2015, Underground Science Conference, SDSM&T 7John Harton, Colorado State University DRIFT spin-dependent limit, 2012 This DRIFT 2012 published limit is pre-minority carrier, 47 day exposure. 2 pb min. These experiments use a spin-dependent target, but they have no directional capability Picasso= super heated droplets of C4F10 - detect acoustic signal upon vaporization NAIAD = small NaI experiment at Boulby KIMs = CsI(Tl) crystals COUPP = super heated bubble chamber with F (old limit)

18-20 May 2015, Underground Science Conference, SDSM&T 8John Harton, Colorado State University DRIFT progress on backgrounds Alphas give a ≈30 cm track Gammas/electrons produce a ragged track Radon and its recoil progeny have been a main background Especially difficult on the central cathode. Two complementary solutions: Texturized thin film cathode (Univ. New Mexico) Minority O 2 charge carriers (Occidental College)

18-20 May 2015, Underground Science Conference, SDSM&T 9John Harton, Colorado State University6/13/13John Harton, CSU Physics9 Radon progeny can drift to the cathode and decay there. Subsequent alpha may bury in the cathode, with the recoil nucleus being indistinguishable from a WIMP event. Two ways to defeat this process: (1) prevent alpha from getting lost in the cathode (2) determine where in z the second decay occurs – fiducialization. Z cathode made of 20 um wires

18-20 May 2015, Underground Science Conference, SDSM&T 10John Harton, Colorado State University DRIFT thin film central cathode Univ. New Mexico: E. Lee, D. Loomba, E. Miller Thin film with ≈ 200 μ texture Film blasted with glass spheres 99.5% α / RPR rejection earlier wire cathode new texturized thin film cathode

18-20 May 2015, Underground Science Conference, SDSM&T John Harton, Colorado State University11 DRIFT thin film cathode radio contamination Univ. New Mexico: E. Miller

18-20 May 2015, Underground Science Conference, SDSM&T 12 DRIFT minority O 2 charge carriers Occidental College: D. Snowden-Ifft O 2 provides faster- drifting carriers Successful test with neutron source proves utility in DRIFT-IId detector at Boulby Standard running with O 2 is so far background free  DRIFT is volume limited John Harton, Colorado State University

18-20 May 2015, Underground Science Conference, SDSM&T 13John Harton, Colorado State University Latest DRIFT result, with zero background Two other directional detectors DRIFT 2012 DRIFT 2014, same running time as 2012 result, 2x better limit. New trigger gives 3x further improvement, results soon. Non-directional detectors DRIFT 2014

18-20 May 2015, Underground Science Conference, SDSM&T 14John Harton, Colorado State University R&D and preparation of D-IIe 1m 3 prototype for a larger detector UK: gas system, mine coordination UNM: drift cage, HHV, cathode Occidental College: drift chambers, electronics front end, fiducialization CSU: front end and digitization electronics Plus Hawaii & Wellesley Preparations at Occidental College, Los Angeles

18-20 May 2015, Underground Science Conference, SDSM&T 15John Harton, Colorado State University CSU electronics at Occidental College

18-20 May 2015, Underground Science Conference, SDSM&T 16John Harton, Colorado State University Questions?