The Search for Axion Dark Matter

Pierre SikivieU of Florida

Fermilab ColloquiumNov. 15, 2006

Outline

• Introduction

• Axion cosmology

• Dark matter axion detection

• Solar axion detection

• Laser experiments

g

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The Strong CP Problem

Because the strong interactions conserve P and CP, .

2

QCD 2...

32a ag

L G G

1010

The Standard Model does not provide a reason for to be so tiny,

but a relatively small modification of the model does provide a reason …

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1 ton

If a symmetry is assumed,

relaxes to zero,

PQU (1)

2

2

1... .

32 2a a

a

a gL G G a a

f

a

a

f

and a light neutral pseudoscalar particle is predicted: the axion.

f f

a

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610 GeVeV

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= 0.97 in KSVZ model 0.36 in DFSZ model

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Searching for the pooltable oscillation quantum

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The invisible axion ?

laboratory searches

510 15101010 (GeV)af

(eV)am 1 510 1010

stellar evolution

g

Relic pooltable oscillations

1 ton

The remaining axion window

laboratory searches

510 15101010 (GeV)af

(eV)am 1 510 1010

stellar evolution

cosmology

Thermal axions

q

ga

these processes imply an axion decoupling temperature

D

1

3

0

106.75) 0.908 K(a

NT t

thermal axion

temperature today:

DN = effective number of thermal degrees of freedom at axion decoupling

11D 12

2

3 10 GeV10 GeV

afT

There are two axion populations: hot and cold.

When the axion mass turns on, at QCD time,

1T

1t

1 1 GeVT 71 2 10 sect

91

1

1) 3 10 eV(ap t

t

Axion production by vacuum realignment

2 2 21 1 1 1

1

1

2

1

2( ) ( ) ( ) ( )a a at t t t

tn m a f

GeVT GeVT

V

a

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1

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3 7

60 1( ) ( )a aa a

R

Rt tm mn

initialmisalignmentangle

Axions are cold dark matter

Density

Velocity dispersion

Effective temperature

75610 eV

aa m

25 3

0, eff10 eV

aa

T tm

55 6

170

10 eV10v

aa

mct

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Axion dark matter is detectable

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conversion power on resonance

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search rate for s/n = 4

2

20 La a

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2 10 Watt

1.2 GHz

year n

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T

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dt

ADMX Collaboration

LLNL: S. Asztalos, C. Hagmann, D. Kinion,

L.J Rosenberg, K. van Bibber, D. Yu

U of Florida: L. Duffy, P. Sikivie, D. Tanner

NRAO: R. Bradley

Axion Dark Matter eXperiment

High resolution analysis of the signal may reveal

fine structure …

ADMX hardwarehigh Q cavity experimental insert

ADMX hemt amplifiers

ADMX MedRes limits

Upgrade with SQUID AmplifiersIB

Vo (t)

The basic SQUID amplifier is a flux-to-voltage transducer

SQUID noise arises from Nyquist noise in shunt resistancescales linearly with T

However, SQUIDs of conventional design are poor amplifiers above 100 MHz (parasitic couplings).

Flux-bias to here

ADMX Upgrade: replace HEMTs (2 K) with SQUIDs (50 mK)

In phase II of the upgrade, the experiment is cooled with a

dilution refrigerator.

SQUIDs packaged into amplifiers

Darin KinionSQUIDs mounted on fridge

4 cavity array – engineering run

Piezo motors have low power dissipation, work at

low temperatures and high magnetic fields

3v10

c

2 21

2)ah m c

1aQ

1LQ

dP

d

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The cold dark matter particles lie on a 3-dimensional sheet in

6-dimensional phase space

the physical density is the projection of the phase space sheet onto position space

z

z.

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The cold dark matter particles lie on a 3-dimensional sheet in

6-dimensional phase space

the physical density is the projection of the phase space sheet onto position space ( , t) = t) ( , t)r r rv v

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z

z.

The cold dark matter particles lie on a 3-dimensional sheet in

6-dimensional phase space

the physical density is the projection of the phase space sheet onto position space ( , t) = t) ( , t)r r rv v

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z

z.

Phase space structure of spherically symmetric halos

Implications:

1. At every point in physical space, the distribution of velocities is discrete, each velocity corresponding to a particular flow at that location.

2. At some locations in physical space, where the number of flows changes, there is a caustic, i.e. the density of dark matter is very high there.

(from Binney and Tremaine’s book)

Galactic halos have inner caustics as well as outer caustics.

If the initial velocity field is dominated by net overall rotation, the inner caustic is a “tricusp ring”.

simulations by Arvind Natarajan

The caustic ring cross-section

an elliptic umbilic catastrophe

D-4

On the basis of the self-similar infall model(Filmore and Goldreich, Bertschinger) with angular momentum (Tkachev, Wang + PS), the caustic rings were predicted to be

in the galactic plane

with radii

was expected for the Milky Way halo from the effect of angular momentum on the inner rotation curve.

1,2,3...n

rot max40kpc v j

220km/s 0.26n

na

max 0.26j

Composite rotation curve(W. Kinney and PS, astro-ph/9906049)

• combining data on

32 well measured

extended external

rotation curves

• scaled to our own galaxy

The Big Flow

• density

• velocity

• velocity dispersion

24 35 1.7 10 gr/cmd

previous estimates of the total local halo density range from 0.5 to 0.75 10 gr/cm-24 3

in the direction of galactic rotation

in the direction away from the galactic center

5 (470 100 ) km/sv r

ur $ $

5v m/s

$

r$

an environmental peak, as seen

in the medium

and

high

resolution

channels

L. Duffy et al.

Axion to photon conversion in a magnetic field

Theory

• P. S. ’83• L. Maiani, R. Petronzio and E. Zavattini ’86• K. van Bibber et al. ’87• G. Raffelt and L. Stodolsky, ‘88 • K. van Bibber et al. ’89

Experiment

• D. Lazarus et al. ’92• R. Cameron et al. ‘93• S. Moriyama et al. ’98, Y. Inoue et al. ’02• K. Zioutas et al. 04• E. Zavattini et al. 05

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in vacuum probability

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mq

Cern Axion Solar Telescope

Decommissioned LCH test magnet

Rotating platform

3 X-ray detectors

X-ray Focusing Device

Sunset

Photon detectors

Sunset axions

Sunrise axions

Sunrise

Photon detectors

1a

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L a E BM

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Primakoff conversion of solar axions in crystals on Earth

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Bragg scattering on crystal lattice

Solax, Cosme ’98

Ge

DAMA ‘01

NaI (100 kg)

Detecting solar axions using Earth’s magnetic field

by H. Davoudiasl and P. Huber

hep-ph/0509293

Sun Eartha

0B

For axion masses , a low-Earth-orbit x-ray detector with an effective area of , pointed at the solar core, can probe down to , in one year.

1( )a

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Rotation

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Rotation and Ellipticity

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Experimental observation of optical rotation generated in vacuum by a magnetic field

the average measured optical rotation is

(3.9 0.5) 10 rad/pass

through a 5 T, 1 m long magnet

by E. Zavattini et al. (the PVLAS collaboration)Phys. Rev. Lett. 96 (2006) 110406

-12

PVLAS

The PVLAS result can be interpreted in terms of an axion-like particle b

inconsistent with solar axion searches, stellar evolution

descrepancy may be avoided in some models

E. Masso and J. Redondo, hep-ph/0504202

I. Antoniadis, A. Boyarski and O. Ruchayskiy, hep-ph/0606306

R.N. Mohapatra and S. Nasri, hep-ph/0610068

1

b

bM

L b E B

5 61 10 GeV 6 10 GeVbM

0.7 meV 2 meVbm

Vacuum

Phase IPhase II

4He 3He

Shining light through walls

K. van Bibber

et al. ‘87

A. Ringwald ‘03

R. Rabadan,

A. Ringwald and

C. Sigurdson ‘05

P. Pugnat et al. 05

R. Battesti et al.

A. Afanasev et al.

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Macroscopic forces mediated by axions

Theory:

J. Moody and

F. Wilczek ’84

Experiment:

A. Youdin et al. ’96

W.-T. Ni et al. ‘96

5f

f ffa fa

mf

fL a i fg

forces coupled to the f number density

forces coupled to the f spin density

1710f background of

magnetic forces

Conclusions

Axions solve the strong CP problem and are

a cold dark matter candidate.

Axions haven’t been found yet.

If axions exist, they are present on Earth as

dark matter and emitted by the Sun.

If an axion signal is found, it will provide a rich source of information on the structure of the Milky Way halo, and/or the Solar interior.

Telescope search for cosmic axions

M.S. Bershady, M.T.Ressell

and M.S. Turner ’90

galaxy clusters

3 – 8 eV

B.D. Blout et al. ‘02

nearby dwarf galaxies

298 – 363 eV

a

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