P. Sikivie- The ADMX search for axion dark matter

8/3/2019 P. Sikivie- The ADMX search for axion dark matter

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The ADMX search foraxion dark matter

P. Sikivie (CERN & U. of Florida)

Moriond 2006

La Thuile, March 16, 2006


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Outline

Introduction

Axion cosmology

Dark matter axion detection

the Axion Dark Matter eXperiment

Phase-space structure of CDM halos

A high resolution search


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The Strong CP Problem

Because the strong interactionsconserve P and CP, .

2

QCD 2...

32

a 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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If a symmetry is assumed,

relaxes to zero,

PQU (1)

2

2

1

... .32 2

a a

a

a g

L G G a af

= + + + ..

%

a

af

=

and a light neutral pseudoscalarparticle is predicted: the axion.


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f f

a

a

6

10 GeVeVa

af

m 6

a

a

a L g E B

f

=

ur ur

= 0.97 in KSVZ model0.36 in DFSZ modelg

5fa f fa

a L i g f f

f=


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The remaining axion window

laboratorysearches

5

10

15

10

10

10(GeV)

a

f

(eV)am 1510 1010

stellar

evolution

cosmology


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Axions are cold dark matter

Density

Velocity dispersion

Effective temperature

75

610 eVa

am

25 3

0,eff

10 eVa

aT t m

34

) 10 (

55 6

17

0

10 eV10v

a

am

ct

) 3

(


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There are two axion

populations: hot and cold.

When the axion mass turns on, at QCD time,

1T

1t

1 1 GeVT7

1 2 10 sect

91

1

1) 3 10 eV(ap t t

=


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Axion production by vacuum realignment

2 2 2

1 1 1 1

1

1

2

1

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

tn m a f

GeVT 1 GeVT 1

V

a

V

a

1

0

3 7

60 1( ) ( )a aa a

R

Rt tm mn

initialmisalignmentangle


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If inflation after the PQ phase transition

2

2IHa

< >

1

( )a I

a a

H

f t

6 10

.may beaccidentallysuppressed

. producesisocurvaturedensity perturbations

isocurvature CMBR constraint

75 6

2

1

10 eV0.25 ( )

aat

m


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If no inflation after the PQ phase transition

. cold axions are produced by vacuumrealignment, string decay and wall decay

.

75 610 eV0.5

a

am

axion miniclusters appear

5

5

313

mc

10 eV10

a

M Mm

5

1

613

mc

10 eV10 cm

a

lm


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Axion dark matter is detectable

a

a

a L g E B

f

=

ur ur

0Bur

a

X

A/D FFT0Bur001TME

ur


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3v 10c

=

2 21

2 )ah m c = (1 +

1

aQ

1LQ

dP

d

2/am hc

610aQ


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conversion power on resonance

a

2

022

500 liter 7 Tesla 0.42 10 Watt

BV C =

2 2

25 3 50.36 5 10 gr/cm GHz 10

La ag m Q

h

c

search rate for s/n = 4

2

2

0 La a

a

gP V B

f

C m Q

1 =

22

22

3

2 10 Watt

1.2 GHz

year n

P K

T

df

dt

=


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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


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Axion Dark Matter eXperiment


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High resolution analysis ofthe signal may reveal

fine structure


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ADMX hardware

high Q cavity experimental insert


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ADMX hemt amplifiers


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ADMX MedRes limits


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Upgrade with SQUID Amplifiers

IB

Vo (t)

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

SQUID noise arises from Nyquistnoise in shunt resistance

scales linearly with T

However, SQUIDs of conventionaldesign are poor amplifiers above100 MHz (parasitic couplings).

Flux-bias to here


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ADMX Upgrade: replace HEMTs (2 K)

with SQUIDs (50 mK)

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

dilution refrigerator.


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SQUIDs packaged into amplifiers

Darin KinionSQUIDs mounted on fridge


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From outwards-in:

Iron shieldCryoperm (mumetal) shieldsSuperconducting shieldsSQUID amplifier packageSQUIDs

The upgrade will be sensitive tothe more pessimistically-coupledaxions even if they are a minorityfraction of the dark-matter halo.

The magnetic field needs tobe cancelled at the locationof the SQUID.


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4 cavity array engineering run

Piezo motors have low power dissipation, work atlow temperatures and high magnetic fields


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3v 10c

=

2 21

2 )ah m c = (1 +

1

aQ

1

LQ

dP

d

2/am hc

610aQ


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The cold dark matter particles lie on

a 3-dimensional sheet in6-dimensional phase space

the physicaldensity is theprojection ofthe phase

space sheetonto positionspace ( , t) = t) ( , t)r r rv v( +

ur r r ur r

z

z.


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The cold dark matter particles lie on

a 3-dimensional sheet in6-dimensional phase space

the physicaldensity is theprojection ofthe phase

space sheetonto positionspace ( , t) = t) ( , t)r r rv v( +

ur r r ur r

z

z.


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Implications:1. At every point in physical space, the

distribution of velocities is discrete, eachvelocity corresponding to a particular flow

at that location.

2. At some locations in physical space, where

the number of flows changes, there is acaustic, i.e. the density of dark matter is veryhigh there.


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Phase space structure of

spherically symmetric halos


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(from Binney and Tremaines book)


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simulation by Arvind Natarajan


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The caustic ring cross-section

an elliptic umbilic catastrophe

D-4


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The Big Flow

density

velocity

velocity dispersion

24 3

5 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 50

P. Sikivie- The ADMX search for axion dark matter

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