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_______________________________ADMX
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
_______________________________ADMX
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