Axion Dark

Matter eXperiment

Steve AsztalosLLNL

Collaborators: UC Berkeley, U Florida, NRAO

TAUP ‘03

Sky&Telescope Nov, 2000

The Nature of Dark MatterMass and Energy Content of the Universe

Wm, the density of all matter.Wb, the density of “ordinary” matter.

WL, the “dark energy” density.

Three important components:≡Wi

ri /rc

Âi

Wi ~ 1

Axions, WIMPs, etc.

If you see an EDM: T + CPT = CP

The discrete symmetry “mirrors”

T ≡ time reversal

C ≡ changing particles to antiparticles

P ≡ space inversion

spinningball

Tmirror

J

J

dE dE

The story of spinning balls, electric dipole momentsand CP violation

Axion PhysicsSearching for Strong CP Violation

q

fine tuning

q

dynamics

mass

pivot

by turning screws

by itself

Here’s what happened:

Added a potential V = mg (1— cosq)

Pool table settled to

Sikivie, Physics Today, 1996

Axion Physics Sikivie’s Pool Table Analogy...

The axion is a pseudoscalar whose mass is a priori unknown

Low-mass axions are good dark matter candidatesbut couple feebly, and thus are hard to detect

Cosmological Connections

Axion couplings: It can do most anything a p0 can do

For example:

Produced cold (in early universe phasetransition). They never thermalize

The combination of accelerator searches,astrophysical and cosmological arguments leaves a

search window 10-6 < ma < 10-3 eV

Cosmological ConnectionsConstraints circa 1995

Cosmological ImplicationsSummary of Constraints

Discovering massive axions still solves the strong-CP problem, but not the dark matter problem.

Hence the emphasis on searches for light axions.

ADMXCARRACKCAST

Sikivie, 1983

a

g

nearby galactichalo axion

microwavephoton

virtualphoton

cryogenic high Qmicrowave cavity

high fieldsolenoidalmagnet

ultra-low noisedetector

cavity electric field

externalmagnetic field

Condition forresonant conversion:hn @ mac2

powerdensity

frequency

axion signal, width J(10-6 n0)

electronicscavity thermal

system output:

Local axion number density ~ 1013/cc

Microwave Cavity Approach _______________________ADMX

_______________________ADMXSingle Cavity Tuning

Axion mass is unknown

Cavity must be tuneable.

50 cm

300 MHz < Tuning range < 800 MHz

n0 (TM010) = 0.115/R GHz

Single Cavity Tuning

Tuning motion accomplishedby 40000:1 reduction gears (~100 nm radial displacement)

_______________________ADMX

Cavity, amplifier and drives @1.3 K in 4-7 Tfield

_______________________ADMXReceiver Chain

Hi-resolutionMedium-resolution

Not so different from your FM tuner…

…except that its sensitivity approaches 10-24 Watts

_______________________ADMXMedium Resolution Receiver Chain

Data Processing

We see statistical peaks, environmental interference,and calibration signals

frequency (MHz)devi

atio

n fr

om m

ean

pow

er (

std

devi

atio

ns) calibration signal

log

num

ber

deviations

Calibrationpeak

Spectra are combined

_______________________ADMX

Recent results

550 to 810 MHz (single cavity)ApJL, Asztalos et al., 571, L27 (2002)PRL, 80, Hagmann et al., 2043-2046 (1998)

1.1 GHz (four cavities)PhD Thesis D. Kinion DAS (2001)

461 to 550 MHz(single cavity)PRDr D.B.Yu et al. (2003?)

_______________________ADMX~ 10-22 Watts !

Recent results (cont.) _______________________ADMX

Increased sensitivity translates into ~ 25% increasein scanning speed

Hi-res channel increases our search sensitivity; anysignal would contain a time-ordered history of

galaxy formation.

_______________________ADMXHigh Resolution Data

Below 440 MHz our search becomes ponderous…How can it be sped up?

Search rate at fixed SNR:

Already near maximum for copper

bigger B: 10-12 Tesla $5M+bigger B: 10-12 Tesla $5M+bigger V: larger center bore magnetsmaller TN: SQUID amplifiers

*All SQUID data and figures that follow: Berkeley: J.Clarke, M-.Andre Giessen: M.Muck

SQUIDS – A Path to an Upgrade

Great success in applying DC SQUIDS tomicrowave amplification*

_______________________ADMX

Increase B,V; decrease TN

fi t ~ TN2

1st decade sensitivity to even pessimistic axioncouplings at fractional dark matter halo density

Near Quantum-LimitedAmplification _______________________ADMX

Upgrade Mechanical Layout

Merely replacing our HEMT amplifiers withSQUIDS will increase our scan speed 4x.

The SQUIDS will occupy a field-free regioncreated by a bucking coil; design is well advanced

Entire upgrade successfully through SAGENAPand Lehman reviews.

_______________________ADMX

Conclusions

• The resolution of the Strong CP Problem is verylikely due to a new chiral symmetry. Axions are anatural solution and is an excellent cold dark mattercandidate.

• ADMX is now in its 7th year of operation. Duringthis latest run we have:

- Deployed lower noise HEMT amplifiers- Taken an additional 90 MHz of data- Shown to have perhaps the lowest noise receiver in the world.- Analyzed data to achieve a better sensitivity- Implemented and analyzed a high resolution data channel

• DOE OS has essentially committed to a FY ’04axion upgrade

Outline

Introduction: The nature of dark matter

Axion physics: born in particle physics…

Cosmological connections: …but findsa home in cosmology

Axion searches: ADMXNew results using a new analyis techniqueNew data from a separate data channelNew future?

Conclusions

Mass density of cluster based on inversion of gravitationallensing. 98% of the mass is a smooth component.

Tyson et al., 1998

M/L, virial theorem, gas x-ray temperatures, Sunyaev-Zel’dolvich effect, gravitational lensing,

Indirect - microwave background, deep redshift supernovae

~30% of the matter in the universe is in someunknown, exotic form.

The Nature of Dark MatterDetection Methods

Gravitational lensing from galaxy cluster 0024-1654

}“Direct”

If the spinning ball is a neutron:

Harris et al., 1999

Quite surprising (in QCD)

Naively

Thus the “Strong CP Problem”:Why is |q| < 10-9, or, equivalently,

Why is QCD CP so small?

Axion PhysicsLimits on the Electric Dipole Moment

If the spinning ball is an electron:

Romalis, Griffith, Jacobs,Fortson, 2001 (on 199Hg)

Not too surprising (in QED)

Or, e.g., less naivelyCrewther,Di Vecchia,Veneziano,Witten, 1979

• ADMX- Axion Dark Matter eXperimentFlorida, LBNL/Berkeley, LLNLC Hagmann, et. al, Phys. Rev. Lett. 80, 2043 (1998)SJ Asztalos, et.al, APJL 571 27 (2002)

Conventional HFET amplificationLarge volume, high field magnet1.2K pumped 4He coolingCosmological axions in the galactic halo

Exotic single photon Rydberg atom detectorLow volume, high field magnet10mK dilution refrigerator coolingCosmological axions in the galactic halo

• CARRACK - Cosmic Axion Research withRydberg Atoms in a ResonantCavity in KyotoKyotoK Yamamoto, et. al, hep-ph/0101200

Axion Searches Photon Conversion Experiments

• CAST – CERN Axion Solar Telescope IG Irastorza, et. al, astro-ph/0211606

Low volume, high field magnetNon-cosmological axions coming fromthe sun

Search for axions - ongoingSingle cavity tuning limitation

Only the TM010 cavity modehas reasonable form factor

Axion SearchesMultiple Cavities for Higher Masses

10-6 10-5 10-4

0.25 2.5 25.

100 10 1

ma (eV)n (GHz)

D (cm)

?

1 m

_______________________ADMX

Axion Searches4-Cavity Tuning

20 cm

_______________________ADMX

SQUID Schematic Voltage Flux Relation

Berkeley and Giessen:Configure input coil as stripline resonator:

Big technical problem: Parasitic capacitanceon SQUID input coil rolls off gain.

Stripline is resonant at“shunt detuned” frequencywhere parisitic capacityis tuned out.

Z0=50W

Z0=7W

{

open-ended stripline coil

F

Axion SearchesSQUIDs as Microwave Amplifiers

_______________________ADMX

_______________________CARRACK

Axion SearchesCARRACK I and II

CARRACK I – Dilution refrigerator @ 10 mKsuppresses thermal noise, thus accidental excitation ofRydberg atom. System noise limited by thermal, notamplifier noise.

8% scan around 10 meV (acquired before 2000) - datanot yet published.

CARRACK II – Proposed to scan the region 2 meV to50 meV. Present status uncertain.

Platform & magnet cryogenics

Picture taken on 13th aug 2002First provoked quench of the magnet

Igor G. Irastorza, CERN / Zaragoza U. TPC Workshop, Paris, 5-6 December 2002

_______________________________CASTAxion Searches

_______________________________CAST

¸Decommissioned LHC test magnet (L=10m, B=9 T)¸Moving platform (to allow up to 50 days / year of alignment)¸4 magnet bores to look for X rays¸3 X rays detector prototypes being used.¸X ray Focusing System to increase signal/noise ratio.

Igor G. Irastorza, CERN / Zaragoza U. TPC Workshop, Paris, 5-6 December 2002

Axion Searches

Technology for space X-ray telescopes recycled for CAST

Igor G. Irastorza, CERN / Zaragoza U. TPC Workshop, Paris, 5-6 December 2002

_______________________________CASTAxion Searches

X-ray Focusing Device

Igor G. Irastorza, CERN / Zaragoza U. TPC Workshop, Paris, 5-6 December 2002

x-y image of 6.4 keV x-ray beam in MicroMegas chamber (logscale for density)

_______________________________CASTAxion Searches

X-ray Focusing Device

Improvement of SNR ~ 200 possible

Experiment has taken commisioning data and willsoon begin operation.

_______________________CARRACK

Axion SearchesSingle Photon Counting

Conversion cavity -> Detection cavity -> Selectivefield ionization

Sensitivity of this approach nearly unlimited, intheory, but difficult, in practice, to calculate.