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Searching for dark matter with the ADMX experiment

Gianpaolo Carosi

Lawrence Livermore National Laboratory USA

ADMX Collaboration

UCLA Dark Matter 2010

02/25/2010

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract

DE-AC52-07NA27344.

_______________________________ADMX What is our Universe made of?

• We know neither what the “dark energy” or the “dark matter” is!

• A particle relic from the Big Bang is strongly implied for DM!— WIMPs ?— Axions ?

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Peccei and Quinn:CP conserved through a hidden symmetry

QCD CP violation should, e.g., give a large neutron electric dipolemoment (T + CPT = CP); none is unobserved (10+ orders-of-magnitude discrepancy)

This leads to the “Strong CP Problem”: Where did QCD CP violation go?

1977: Peccei and Quinn: Posit a hidden broken U(1) symmetry 1) A new Goldstone boson (the axion);2) Remnant axion VEV nulls QCD CP violation.

Why doesn’t the neutron havean electric dipole moment?

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Properties of the axion

_______________________________ADMX The dark matter axion - relatively confined parameter space!

KSVZ

DFSZ

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How’s the axion faring as a dark-matter candidate?Wilczek conclusion (“Physics Today”):“I’m much more optimistic about the dark matter problem.Here we have the unusual situation that two good ideas exist…(wimps and axions)”

Witten conclusion (“Axions in String Theory”):Axions are ubiquitous in string theory; as necessary as gravitons.

Couplings and masses of Dark-matter QCD axions are tightlyconstrained:Allowed couplings are within a range of ×7 and the mass isconstrained to the two decades 10-6 –10-4 eV.

The axion remains a very attractive dark-matter candidate(affirmed by HEPAP, DMSAG, etc.)

The ADMX axion search is “definitive” and relatively inexpensive

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Principle of the microwave cavity experiment [Pierre Sikivie, PRL 51, 1415 (1983)]

∆E/E ~ 10–22

Resonance condition:

hν = mac2[ 1 + O(β2~ 10-6) ]

Signal power:P ∝ ( B2V Qcav )( g2 ma ρa )

~ 10–23W

Microwave Cavity

Superconductingmagnet

Amp

MediumResolutionChannel(thermalized) High

ResolutionChannel(coherent)

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ADMX collaboration

University of WashingtonLeslie Rosenberg, Gray Rybka, Michael Hotz, Andrew Wagner, Doug Will, Jesse Heilman, Kyle Tracy, Miguel MoralesUniversity of FloridaDavid Tanner, Pierre Sikivie, Neil Sullivan, Jeff Hoskins, Jungseek Hwang+, Catlin MartinLawrence Livermore National LaboratorySteven Asztalos*, Gianpaolo Carosi, Darrell Carter, Chris Hagmann, Darin Kinion,Karl van Bibber#

National Radio Astronomy ObservatoryRichard BradleyUniversity of California, Berkeley John ClarkeSheffield UniversityEdward Daw

_______________________________ADMX The Experiment

Baffling

Bucking Magnet

SQUID

“1K” Pot

Microwave Cavity

Main Magnet 13 Ton 8 Tesla in center bore

4m4 m

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Currently using copper-plated tuning rodshigh-Q cavity experiment insert

_______________________________ADMX The Axion Dark Matter eXperiment

Stage Phase 0 Phase I Phase II

Technology HEMT; Pumped LHe

Replace w. SQUID

Add Dilution Fridge

Tphys 2 K 2 K 100 mK

Tamp 2 K 1 K 100 mK

Tsys = Tphys + Tamp 4 K 3 K 200 mK

Scan Rate

∝ (Tsys ) –2

1 @ KSVZ 1.75 @ KSVZ 5 @ DFSZ

Sensitivity Reachg

2 ∝ Tsys KSVZ 0.75 x KSVZ DFSZOR AND !

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Details of data acquisition & analysis

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Sample data and candidates

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Conversion microwave photons are detected byone of the world’s quietest radio receiver

Systematics-limited for signals of 10-26 W~10-3 of DFSZ axion power (1/100 yoctoWatt).

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Prior ADMX results

Three eras of (early) ADMX “Phase 0” (non-SQUID) operations

Single cavity/medium-resolution channel• 1995 to 1998, 2001 to 2003

– PRL 80 (1998) 2043 (PhD Thesis)– PRD 64 (2001) 092003– PRD 69 (2004) 011101(R) (PhD Thesis)

Four-cavity/medium-resolution channel• 1999 to 2001

– PhD ThesisSingle cavity/high-resolution channel

• 2003 to 2004– PRL 95 (2005) 091304 (PhD Thesis)

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Phase I & II Upgrade path:Quantum-limited SQUID-based amplification

•SQUIDs have been measured with TN ~50 mK

•Near quantum– limited noise

•This provides an enormous increase in ADMX sensitivity

_______________________________ADMX Phase I upgrade (Started data taking in May 2008)

Field compensationmagnet for SQUIDs

SQUIDamplifier

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Now running in Phase I (SQUID amplifiers)

• Injected Power

• Noise floor

_______________________________ADMX ADMX Phase I: Accomplishments to date.

Successfully operated experiment with SQUID amp near 7 Tesla field

Received: Oct 27th, 2009Accepted: Dec 22nd, 2009Published: Jan 29th, 2009DOI: 10.1103/PhysRevLett.104.041301

Covered 812 – 860 MHz = 48 MHz

Total Run Time: 19 months

Continuous Data Collecting: 8 months

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FY09 Phase I reach

PVLAS (retracted)

Phase 07 years

Phase I2009

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Periodic-post resonators(10-100 GHz)

Phase II: SQUID amplifiers plus dil fridge Ts ~ 200mK

Single cavity with SQUID amplifiers and dilution refrigerator

300 < f < 3 GHzT ~ 200 mK

Plans to move and install at

University of WashingtonT

s 200 mK = 150 mK + 50 mK

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Phase II ADMX: Add dilution-refrigerator cooling

Phase II will scan the lower-mass decade at or below DFSZ sensitivity, then continue upward in frequency

This is the “definitive” search

_______________________________ADMX Utilizing ADMX for a Chameleon search

Chameleons: Particles whose mass depends on local matter density.(possible dark energy particle)Can mix with photons but have trouble moving through walls.

_______________________________ADMX Utilizing ADMX for a Chameleon search

_______________________________ADMX Summary and Conclusions

• Successfully operated SQUID amplifier near 7 T B-field at pumped LHe temperatures (~ 2 k).

• Took Med. Resolution data at KSVZ sensitivity (812-860 MHz): Published results in PRL!

• Currently taking data to close out High Resolution channel. (will continue data-taking in both channels until April).

• Chameleon particle search: Proof of Principle (will be submitted for publication soon)

• Currently preparing for move magnet to UW in May/June timeframe. Phase II contruction (Dilution fridge + New Insert). DEFINITIVE SEARCH!

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Status of Electric Dipole Moment Searches

* Baker, C. A.; et al. (2006). "Improved Experimental Limit on the Electric Dipole Moment of the Neutron". Phys. Rev. Lett. 91: 131801. http://link.aps.org/abstract/PRL/v97/e131801.

*

Currently, there are at least four experiments aiming at improving the current limit (or measuring for the first time) on the neutron EDM with a sensitivity down to 10-28 e-cm over the next 10 years

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Properties of the axion

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Phase I operations:“Chameleons”& hidden-sector photons (1)

Chameleons Hidden-sector photonsScalars/pseudoscalars that mix withphotons, and are trapped by cavitywalls. Arise in some dark energytheories. Detectable by slow decayback into photons in cavity

Vector bosons with photon quantumnumbers and very weak interactions.Detectable by reconverting HSPs backinto photons in ADMX cavity

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Phase I operations:“Chameleons”& hidden-sector photons (2)

Chameleons Hidden Sector Photons

One day of running in June set limits comparable to GammeV experiment.

Jaeckel & Ringwald (2009)Apply ADMX limits on HSP coupling.

GammeVLimit