drift i experiment for dark matter search dark matter review setupand installation results. r&d...
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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
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
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
...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)
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
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.