DRIFT I experiment for Dark Matter Search Dark Matter Review Setupand Installation Results. R&D for DRIFT II. Conclusion. Rachid Ayad, Temple University, for: R. Ayad, C. J. Martoff, M. Schachter Temple University, PA, USA J. Kikpatrick, D. P. Snowden Occidental College, CA, USA T. B. Lawson, P. K. Lightfoot, B. Morgon, M. Robinson, N. J. C. Spooner. University Of Sheffield, UK

Evidence Of Dark Matter Zwicky (1930): From speed and mass of galaxies, galaxies cannot hold together Later on, same problem with galaxies: stars orbit too fast to be bound by visible light.

WMAP(Wilkinson Microwave Anisotropy Probe) CMB photons (Cosmic Microwave Background) decoupled during the Big Bang at a temperature of ~ 3K: For a flat universe the size of cluster is ~ 1 Deg., so  ~1 With the help of other peaks, WMAP was able to give:  tot = /  dark-energy = /  CDM = /  baryonic = / A. Kosowsky et al Phys. Rev. D, 66, 63007, astro-ph/ , and astro-ph/

AnodeWires Bottom MWPC (512 Chans) Top MWPC (512 Chans) DAQ RACK Slow Control RACK

VME ADC BAORD Ribbon Connector 32 wires TPC Input Gain: -Full range: 2.4 pC -1pC/V,~4000 e - /adc count Shaper: -24  Sec FWHM Digitizer: -Resolution: 12bits -Sampling Rate: 1MS/sec -Buffer Memory Depth: 16K Samples/Channel -Relative Accuarcy: +/- 1 LSB

Electronic Calibration

Trigger System

(modified comedi driver)

Gas Gain Calibration Using Fe55 Source Escape Peak Gain= (2998*158)/300 ~ 1579

Neutron Calibration Send Neutrons from 252Cf source: dN/dE = sqrt(E)exp(-E/T) T = 1.3 MeV Use Geant3 to generate nuclear recoil and dE/dX Garfield drifts Primary Negative Ions to the anode wires. Simulated Neutron Event

Erecoil = W*NIPS W = 45 eV +/- 5 eV

...we need neutron shielding to achieve proposal goals. Unshielded vesselWith.5m (8 tons) CH 2 shielding (installed March 23, 2004)

Daya Analysis Analysis based on 400 GB recorded data.  ~ 70,000 triggers  trigger rate (veto rejection) below.05 Hz

More Events Clean neutron recoil Range-Energy from 252-Cf source green; unshielded n 90% limit red: shielded n 90% limit (shielded, no software veto)

Analysis Procedures DST produced; then 14 simple, fully automated cuts applied

Bottom Line Two independent analyses (Temple, Oxy-Sheffield) consistent on this effect. Unshielded: 2.4 +/ events per day Shielded: 1.1 +/ events per day Rates: Shielding Effect: 1.3 +/- 0.62

still zero Accepted Background: still zero

Focus on WIMP region Events below the 90% neutron line are WIMP candidates or background neutrons. One event in 9 days unshielded data looks like a room neutron 5 more below 1000 NIPS are probably neutrons. Nuclear Recoil Zone

R&D for DRIFT II and Helium Mixtures NI drift and gain works fine with GEMs (physics Miyamoto et al [experiments run at Temple Univ.] allow pixelization to few 100 um with row-and-column readout Helium mixtures with CS2 also studied in TPC prototype at Temple Univ., physics Helium buffer gas allows NI drift and gain at total pressure 1 bar  NO vacuum vessel- great cost and BG savings

Conclusion DRIFT I showed that negative ion gases can be used in TPCs for Dark Matter Search: No need to magnetic field. Promising low background capability. Upgrade to DRIFT II is at the development phase: - - Use GEM or TPCs at 1 bar, with light buffer gas, which will reduce the cost of a vacuum vessel and its maintenance. - Use large mass of ionizing medium for WIMP limit study and directionality study/rejection.

WIMP Direct Experiments DAMA (Dark Matter Search): In Gran Sasso, with 100 kg target NaI scintillator crystal,, where nuclear recoil/ electron-gamma Ionization rejection is achieved by Pulse Shape discrimination m deeper CDMS “Cryogenic Dark Matter Search”: 0.52 Kg of Ge/Si, where Nuclear recoil/electron-gamma Ionization rejection by comparing phonon surface heat to Ge/Si ionization. 10 m deeper (Now In Soudan) EDELWEISS “Experience pour DEtecter Les Wimps En Site Souterrain” In Modane Site”: 0.32 Kg of Ge/Si, where Nuclear recoil/electron-gamma Ionization rejection by comparing phonon surface heat to Ge/Si ionization m deeper ZEPLIN “Zoned Proportional scintillation in Liquid Noble gases” In Boulby Mine: 3kg of Pure Xenon, where Excited Xenon* gives two Gamma Rays that can be discriminated for Nuclear recoil/electron- gamma ionization by pulse height m deeper.

Nuclear-Electron Recoil Rejection in Ge/Si detector

DM experiments Upper limits

CS2-He(Ar) GEM test at Temple Univ.