DRIFT I experiment forDark 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 = 1.02 +/- 0.02

dark-energy = 0.73 +/- 0.04

CDM = 0.27 +/- 0.04

baryonic = 0.044 +/- 0.004

A. Kosowsky et al Phys. Rev. D, 66, 63007, 2002.astro-ph/0302218, and astro-ph/0302207

AnodeWires

Anode Wires

Bottom MWPC (512 Chans)

Top MWPC (512 Chans)

DAQ RACKSlow Control RACK

VME ADC BAORD

Ribbon Connector32 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 CalibrationSend 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 vessel With .5m (8 tons) CH2 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 EventsClean 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 +/- 0.52 events per day

Shielded: 1.1 +/- 0.33 events per day

Rates:

Shielding Effect: 1.3 +/- 0.62

Accepted Background: still zerostill 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 RecoilZone

R&D for DRIFT II and Helium Mixtures

NI drift and gain works fine with GEMs (physics-0310124 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-0406114.

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. 1400 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. 1700 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. 1100 m deeper.

Nuclear-Electron Recoil Rejection in Ge/Si detector

DM experiments Upper limits

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