Searches for Dark Matter the Quest

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Searches for Dark Matter(the Quest)

• Harry Nelson
• UCSB
• 2003 SLAC Summer Insitute
• Aug. 5-6 2003

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Plan

• Introductory Material
• Axions
• Massive Particles
• Direct Detection
• Strongly Interacting
• Weakly Interacting
• Indirect Detection
• charged/milli-charged
• Concluding Material

Small calculations, supporting material
interspersed my goal is to develop a feel
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Some Sources

• M. Srednicki, 1994 SLAC Summer Institute
  http//www.slac.stanford.edu/pubs/confproc/ssi94/s
  si94-010.html
• M. Perl et al., 2001 http//www.slac.stanford.edu/
  pubs/slacpubs/8000/slac-pub-8772.html
• IDM 2002 http//www.shef.ac.uk/phys/idm2002/talks
  /
• SPIRES http//www.slac.stanford.edu/spires/hep/
• NASA Astrophysics Data System http//adswww.harvar
  d.edu/index.html

Apologies for figures not perfectly acknowledged
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The Milky Ways Dark Halo (?)
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The Dark Ball
Dark Matter Halo
Bulge
Disk
Why havent dark matter particles fall into our
disk?

• Dark particles scarcely interact with us and/or
• Dark particles very heavy

(150 passes/age of U)?(0.3 to 2) ? 10-2 gm/cm2 ?
(0.5 to 3) gm/cm2 not very restrictive
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Theoretical Guidance Caveat Emptor
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Remainder of L. Alvarez Essay
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Talavera reviewed Columbus
12,000 km (Talavera, accurate)
5,000 km (Columbus, fudged systematics)
Both simplified the intervening region to pure
ocean
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Usual Simplifications of Dark Matter

• Local energy density, apparent speed of DM
• Consists of one elementary particle (!)

0? (200-2000)
(170-270)
from galactic astrophysics
? , ?e,m,t , e- , p , n - 7 in our few percent
of Univ.
2 are composite n ??
The DM particle that provides the clearest signal
in a search might not be the most abundant a
strong argument for an eclectic mix of search
techniques.
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Advice of Dennis the Menace
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Usual Simplifications of Dark Matter

• DM not baryons (CBR, BBN Eros/MACHO)
• DM was once in thermal equibrium

mass gt few keV (large scale structure) mass lt 340
TeV (unitarity) cross section with us ? weak
(10-44-10-36 cm2) little unknown missing energy
at LEP, Tevatron massgt10s GeV
Weakly Interacting Massive Particles
SUSY restored just above weak scale gives WIMPS
Attractive candidates (axions, zillas, etc.)
were never in thermal equilibrium
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Scope

• Keep an open mind

? ?e,m,t e- ?0 p n
-- Our Matter
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Direct Detection

• Momentum Transfer

axion
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Axions (and similar)
Leslie Rosenberg
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Primakoff Conversion, Microwave Detection
Amplifier power pours out of cavity when B0
applied
LB 50 cm
Solenoid
Cavity, TM mode (E parallel to B0 0- )
Leslie Rosenberg
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Tunable Cavity
Tuning Rods
2 ? Q ? 80 sec/scan ? 1 year
Leslie Rosenberg
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Signal Level and Noise
10-17 W from Pioneer 10 Spacecraft, 1010 km away
?(s/n)
HEMT
10-26 W ?
?(time)
Substantial improvements in Ts are on the horizon
(X30) from increased cooling, SQUIDS
Leslie Rosenberg
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Example of Data, Expected Signal
Leslie Rosenberg
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?eV Axion Future

• ADMX SQUIDs, hope to cover 2 decades in mass
• Kyoto single quantum detector

Leslie Rosenberg
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CAST Axions from the Sun
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Experiment and Expected Sensitivity
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Massive Particles Recoil Kinematics - I
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Recoil Kinematics - II
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Nuclear Recoil Cross Section
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Nuclear Recoil Diffraction
0 110 220 330 keV ER
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Nuclear Recoils from Massive Dark Matter

• Deposit 10s of keV
• For target atomic weight Alt160, dark matter
  velocity spectrum a delta-function, recoil
  spectrum flat up to an endpoint
• Diffraction off nucleus, form factor of nucleus
  directly appear in recoil spectrum
• Cross section favorable as A increases
• Havent focused on magnitude of cross section
  yet
• 10-44-10-36 cm2 (weak) or 10-24 cm2 (strong)
  still fine

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To Penetrate the Atmosphere
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SIMP exclusion (above/below atmos.)
Wandelt et al., astro-ph/0006344
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SIMP Exclusion, Oroville Experiment
Caldwell, Snowmass, 1994
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Guide to Exclusion Plots
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WIMP/nucleon ?p ?10-42 cm2
Exper. CDMS DAMA
Theory SUSY, various constraints including Big
Bang
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Compare with Common Background Rate
? DRU

• Shield (shield radioactive too!) 1 ev/(kg d
  keV) typical
• Reduce the background HDMS , IGEX , Genius
• Exploit astron. properties (year cycle,
  directionality) DAMA, DRIFT
• Devise detectors that can distinguish nuclear
  recoil from electron recoil Edelweiss, CDMS,
  Xenon..

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Germanium Quest for Lowest Background
HDMS at Gran Sasso (3800 mwe (meters water
equivalent) depth)
Inner Germanium (0.2 kg)
Outer Ge (2.1 kg)
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IGEX (2 kg Ge, CANFRANC, 2450 mwe)
BACKGROUND 4-10 keV background 0.22
c/keV/kg/day 10-20 keV background 0.10
c/keV/kg/day 25-40 keV background 0.04
c/keV/kg/day
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KeVee versus KeV (Recoil) Signal Shape
IGEX
KeVee
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IGEX Exclusion Region
IGEX-DM 2000
IGEX-DM 2001 2002
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Genius Program Background Elimination
Suspend Ge detector in Liquid Nitrogen
0.1 events/(kg KeV d)
L 2 m
Genius Test Facility (under construction) 40 kg Ge
Baudis et al., 2001
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Ultimate Genius