Cosmic Axion Detection with an Amplifying B-Field Ring Apparatus

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Cosmic Axion Detection with an Amplifying B-ﬁeld Ring Apparatus

Ben Safdi Massachusetts Institute of Technology

2015 Two important facts to keep in mind in any dark matter talk (at least, today) Fact 1: we know a lot about dark matter Fact 2: we know almost nothing about dark matter Fact 2: we know almost nothing about dark matter

I No evidence for non-gravitational interactions

DM SM DM DM

? ?

DM SM DM DM

I No evidence for particular dark-matter mass Over 20 orders of magnitude in DM mass!

Axions WIMPS

-12 -3 9 12

log10(ma/eV) Dark-matter: BSM physics exists

Axions WIMPS

-12 -3 9 12

log10(ma/eV)

Clear evidence that dark-matter (BSM physics) exists • Well motivated dark-matter models (WIMPs, axions,...) • Dark matter models

Name What is it? Motivation

a µ Axion ✓¯ + G G˜ Strong CP f µ ✓ a ◆

Hierarchy Problem Neutralino (WIMP) B,˜ W˜ 3, H˜u, H˜d (why Higgs mass so light) How can we probe axion dark matter?

Astrophysics Axion helioscope Resonant cavity

BH superradiance CAST

Figure 1: Axionic Black Hole Atom: The spinning black hole “feeds” superradiant states form- ing an axion Bose-Einstein condensate. The resulting bosonic atom will emit gravitons through axion transitions between levels and annihilations and will emit axions as a consequence of self- interactions in the axion ﬁeld. ADMX

Consequently, one may expect hundreds of axion-like particles in a given string compactification. However, a plenitude of cycles does not yet guarantee the presence of a plenitude of axions. There is a number of eects in string theory that could produce a large axion mass, such as branes wrapping the cycles, and fluxes. One can roughly estimate the number of light axions as being Phys. Lett. determined by theAstrophysics/cosmology number of cycles without fluxes—presumably, around one tenth: of stellar the total cooling, CMB, BBN ( number of cycles.• Still this leaves us with the expectation of several tens of axion-like particles. The discoveryB. of 2014: a plenitude K. of particles Blum, in our R. vacuum D’Agnolowith similar properties,M. Lisanti but dierent,B.S.), superradiance masses supports the idea of a plenitude of vacua, as both the axiverse and the multiverse are dynamical consequences of the same fundamental ingredients. The masses of stringLaboratory axions are exponentially sensitive experiments to the sizes of the corresponding: ADMX cycles, (resonant cavity), CAST so one expects• them to be homogeneously distributed on the logarithmic scale. However, given 10 that the QCD ✓-parameter is constrained to be less than 10 , non-perturbative string corrections to the QCD axion(axion potential should helioscope) be at least ten orders of magnitude suppressed as compared to the QCD generated potential. It is then natural to expect many of the axions to be much lighter than the QCDNew axion; these proposal: are the axions whose mass isPRL dominated117, only by these Sept. small 2016 (Y. Kahn, B.S., J. Thaler): A non-perturbative string eects. The implicit,• and very plausible assumption behind this line of reasoning is that there is no anthropic reasonbroadband for the existence and properties approach of the QCD axion. Consequently, to axion these properties dark matter detection ADMX should follow from the dynamics of the compactification manifold, rather than being a result of fine-tuning, and the QCD axion should be a typical representative among other axion-like fields. A priori we expect tens (or even hundreds) of light axions, it would be really surprising if the QCD axion turned out to be the single one.

5 Outline

I Axion particle physics (review)

I Axion cosmology (review and work in progress)

I ABRACADABRA: Cosmic axion detection (theory)

I ABRACADABRA-10 cm at MIT (experiment) Why axions and what are they? Solutions: • I mu =0: but strongly disfavored by lattice data

I Spontaneous CP violation (Nelson-Barr) I ✓¯ =0in UV because theory CP conserving ¯ I After spontaneous CP breaking, CKM generated but ✓ protected (extra structure) I May introduce additional ﬁne tuning, coincidence of scales, signiﬁcant model-building gymnastics

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | I Spontaneous CP violation (Nelson-Barr) I ✓¯ =0in UV because theory CP conserving ¯ I After spontaneous CP breaking, CKM generated but ✓ protected (extra structure) I May introduce additional ﬁne tuning, coincidence of scales, signiﬁcant model-building gymnastics

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data ¯ I After spontaneous CP breaking, CKM generated but ✓ protected (extra structure) I May introduce additional ﬁne tuning, coincidence of scales, signiﬁcant model-building gymnastics

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data

I Spontaneous CP violation (Nelson-Barr) I ✓¯ =0in UV because theory CP conserving I May introduce additional ﬁne tuning, coincidence of scales, signiﬁcant model-building gymnastics

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data

I Spontaneous CP violation (Nelson-Barr) I ✓¯ =0in UV because theory CP conserving ¯ I After spontaneous CP breaking, CKM generated but ✓ protected (extra structure) I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data

10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | 10 Strong CP: the other naturalness problem ( ✓¯ < 10 ) | |

10 Problem: CP-violating O(1), but ✓¯ < 10 • CKM ⇠ | | Solutions: • I mu =0: but strongly disfavored by lattice data

I Axion: Spontaneously broken global PQ symmetry in UV I Light pseudo-goldstone boson “the axion” removes ✓¯ | | I Axion can be dark matter 16 I Calculation: d 2.4 10 ✓¯ e cm n ⇡ ⇥ ·

10 I Measurement: ✓¯ < 10 | |

I No anthropic argument for why ✓¯ is so small!

The axion solves the strong CP problem

2 ✓ g µ⌫ iq5 CP = G G˜ qm¯ e q LQCD 32⇡2 µ⌫ q q X

i↵q5 I U(1) anomaly: q e q A ! ✓ ✓ +2 ↵ ! q q X

I U(1) invariant: ✓¯ ✓ A ⌘ q q X

Peccei, Quinn 1977; Weinberg 1978; Wilczek 1978 10 I Measurement: ✓¯ < 10 | |

I No anthropic argument for why ✓¯ is so small!

The axion solves the strong CP problem

2 ✓ g µ⌫ iq5 CP = G G˜ qm¯ e q LQCD 32⇡2 µ⌫ q q X

i↵q5 I U(1) anomaly: q e q A ! ✓ ✓ +2 ↵ ! q q X

I U(1) invariant: ✓¯ ✓ A ⌘ q q X16 I Calculation: d 2.4 10 ✓¯ e cm n ⇡ ⇥ ·

Peccei, Quinn 1977; Weinberg 1978; Wilczek 1978 The axion solves the strong CP problem

2 ✓ g µ⌫ iq5 CP = G G˜ qm¯ e q LQCD 32⇡2 µ⌫ q q X

i↵q5 I U(1) anomaly: q e q A ! ✓ ✓ +2 ↵ ! q q X

I U(1) invariant: ✓¯ ✓ A ⌘ q q X16 I Calculation: d 2.4 10 ✓¯ e cm n ⇡ ⇥ ·

10 I Measurement: ✓¯ < 10 | |

I No anthropic argument for why ✓¯ is so small! Peccei, Quinn 1977; Weinberg 1978; Wilczek 1978 I Axions also couple to QED:

1 µ⌫ ↵EM = gaaFµ⌫F˜ ga L 4 / fa

The axion solves the strong CP problem

a g2 = ✓¯ + G G˜µ⌫ Laxion f 32⇡2 µ⌫ ✓ a ◆

I QCD generates axion mass:

1 a 2 V (a) f 2m 2 ✓¯ + ⇡ 2 a a f ✓ a ◆ 16 f⇡ 9 10 GeV m m 10 eV a ⇡ f ⇡ ⇡ f a ✓ a ◆

Peccei, Quinn 1977; Weinberg 1978; Wilczek 1978 The axion solves the strong CP problem

a g2 = ✓¯ + G G˜µ⌫ Laxion f 32⇡2 µ⌫ ✓ a ◆

I QCD generates axion mass:

1 a 2 V (a) f 2m 2 ✓¯ + ⇡ 2 a a f ✓ a ◆ 16 f⇡ 9 10 GeV m m 10 eV a ⇡ f ⇡ ⇡ f a ✓ a ◆

I Axions also couple to QED:

1 µ⌫ ↵EM = gaaFµ⌫F˜ ga L 4 / fa

Peccei, Quinn 1977; Weinberg 1978; Wilczek 1978 Outline

I Axion particle physics (review)

I Axion cosmology (review and work in progress)

I ABRACADABRA: Cosmic axion detection (theory)

I ABRACADABRA-10 cm at MIT (experiment) 3 I Local DM energy density: ⇢DM 0.4 GeV/cm ⇡ 3 I Local occupancy number: (⇢DM /m) db 44 N⇡ ⇥ I axion 10 N ⇡ 36 I 10 NWIMP ⇡

Axion dark matterDark is a Matter classical Models ﬁeld

DM ﬁeld DM particles

Axions WIMPS

-12 -3 9 12

log10(ma/eV) 2⇡ 2⇡ I de Broglie wavelength: = dB p ⇡ mv 9 3 I Axion (m = 10 eV): dB 8 10 km ⇡ ⇥ 17 I WIMP (m = 100 GeV): 8 10 km dB ⇡ ⇥ Axion dark matterDark is a Matter classical Models ﬁeld

DM ﬁeld DM particles

Axions WIMPS

-12 -3 9 12

log10(ma/eV) 2⇡ 2⇡ I de Broglie wavelength: = dB p ⇡ mv 9 3 I Axion (m = 10 eV): dB 8 10 km ⇡ ⇥ 17 I WIMP (m = 100 GeV): dB 8 10 km ⇡ ⇥ 3 I Local DM energy density: ⇢DM 0.4 GeV/cm ⇡ 3 I Local occupancy number: (⇢DM /m) db 44 N⇡ ⇥ I axion 10 N ⇡ 36 I 10 NWIMP ⇡ After 3H = m , coherent oscillations NR matter • a ⇠ 7/6 2 fa 2 Today: ⌦ah 0.1 ✓ • ⇠ 1012 GeV i ✓ ◆ 16 3 2 f = 10 GeV ✓ 10 10 (e.g., Tegmark, Aguirre, Rees, Wilczek ’05) • a !| i| .

The axion as dark matter (fa >HI/2⇡) 2 2 a¨ +3Ha˙ + maa =0 (H = T /mpl) After 3H = m , coherent oscillations NR matter • a ⇠ 7/6 2 fa 2 Today: ⌦ah 0.1 ✓ • ⇠ 1012 GeV i ✓ ◆ 16 3 2 f = 10 GeV ✓ 10 10 (e.g., Tegmark, Aguirre, Rees, Wilczek ’05) • a !| i| .

The axion as dark matter (fa >HI/2⇡) 2 2 a¨ +3Ha˙ + maa =0 (H = T /mpl) ✓i = ai/fa

initial 3/2 misalignment a T cos(mat)

L / t H a 3H = ma

Wednesday, December 11, 13 7/6 2 fa 2 Today: ⌦ah 0.1 ✓ • ⇠ 1012 GeV i ✓ ◆ 16 3 2 f = 10 GeV ✓ 10 10 (e.g., Tegmark, Aguirre, Rees, Wilczek ’05) • a !| i| .

The axion as dark matter (fa >HI/2⇡) 2 2 a¨ +3Ha˙ + maa =0 (H = T /mpl) ✓i = ai/fa

initial 3/2 misalignment a T cos(mat)

L / t H a 3H = ma

t After 3H = m , coherent oscillations NR matter • a ⇠

Wednesday, December 11, 13 16 3 2 f = 10 GeV ✓ 10 10 (e.g., Tegmark, Aguirre, Rees, Wilczek ’05) • a !| i| .

The axion as dark matter (fa >HI/2⇡) 2 2 a¨ +3Ha˙ + maa =0 (H = T /mpl) ✓i = ai/fa

initial 3/2 misalignment a T cos(mat)

L / t H a 3H = ma

t After 3H = m , coherent oscillations NR matter • a ⇠ 7/6 2 fa 2 Today: ⌦ah 0.1 ✓ • ⇠ 1012 GeV i ✓ ◆

Wednesday, December 11, 13 The axion as dark matter (fa >HI/2⇡) 2 2 a¨ +3Ha˙ + maa =0 (H = T /mpl) ✓i = ai/fa

initial 3/2 misalignment a T cos(mat)

L / t H a 3H = ma

t After 3H = m , coherent oscillations NR matter • a ⇠ 7/6 2 fa 2 Today: ⌦ah 0.1 ✓ • ⇠ 1012 GeV i ✓ ◆ 16 3 2 f = 10 GeV ✓ 10 10 (e.g., Tegmark, Aguirre, Rees, Wilczek ’05) • a !| i| . Wednesday, December 11, 13 I QCD Damping rate (McLerran et. al. 1990) : 1 ↵ ↵ = d4x s tr[G G˜µ⌫(x)] s tr[G G˜µ⌫(0)] QCD f 2 T h 4⇡ µ⌫ 4⇡ µ⌫ iT a Z sphaleron = 2 fa T T 3 (large coefﬁcient) 2 / ⇥ fa

I Important if H at T 1 GeV: QCD ⇠ ⇠ (1 GeV)3 (1 GeV)2 2 18 fa ⇠ 10 GeV 10 I Important for f 10 GeV (with the (1) numbers) a . O

Is QCD damping relevant at small fa? Preliminary! In progress with Andrey Katz

2 a¨ +(3H + QCD)˙a + maa =0 I Important if H at T 1 GeV: QCD ⇠ ⇠ (1 GeV)3 (1 GeV)2 2 18 fa ⇠ 10 GeV 10 I Important for f 10 GeV (with the (1) numbers) a . O

Is QCD damping relevant at small fa? Preliminary! In progress with Andrey Katz

2 a¨ +(3H + QCD)˙a + maa =0

I QCD Damping rate (McLerran et. al. 1990) : 1 ↵ ↵ = d4x s tr[G G˜µ⌫(x)] s tr[G G˜µ⌫(0)] QCD f 2 T h 4⇡ µ⌫ 4⇡ µ⌫ iT a Z sphaleron = 2 fa T T 3 (large coefﬁcient) 2 / ⇥ fa Is QCD damping relevant at small fa? Preliminary! In progress with Andrey Katz

2 a¨ +(3H + QCD)˙a + maa =0

I QCD Damping rate (McLerran et. al. 1990) : 1 ↵ ↵ = d4x s tr[G G˜µ⌫(x)] s tr[G G˜µ⌫(0)] QCD f 2 T h 4⇡ µ⌫ 4⇡ µ⌫ iT a Z sphaleron = 2 fa T T 3 (large coefﬁcient) 2 / ⇥ fa

I Important if H at T 1 GeV: QCD ⇠ ⇠ (1 GeV)3 (1 GeV)2 2 18 fa ⇠ 10 GeV 10 I Important for f 10 GeV (with the (1) numbers) a . O Is QCD damping relevant at small fa?

11 Probably not if fa & 10 GeV

11 fa = 10 GeV with QCD damping

no QCD

) damping t ( a

t Is QCD damping relevant at small fa?

10 Likely yes if fa . 10 GeV

10 fa = 10 GeV

with QCD damping no QCD )

t damping ( a

t Outline

I Axion particle physics (review)

I Axion cosmology (review and work in progress)

I ABRACADABRA: Cosmic axion detection (theory)

I ABRACADABRA-10 cm at MIT (experiment) How can we probe axion dark matter?

ADMX Limit (axion-DM resonant cavity) IAXO Projected (Axions from the Sun) ADMX Projected

QCD axion (theory) How can we probe axion dark matter?

ADMX Limit (axion-DM resonant cavity) IAXO Projected (Axions from the Sun) ADMX Projected BH Superradiance?

e.g., Arvanitaki, Baryakhtar, Huang 2014 How can we probe axion dark matter?

ADMX Limit (axion-DM resonant cavity) IAXO Projected (Axions from the Sun) ADMX Projected

String/GUT inspired axion DM models Naturally Live Here!

e.g., Svrcek, Witten 2006 I Magnetoquasistatic approximation: new electric current that follows B-ﬁeld lines @a B = g B r⇥ a @t

1 2 2 I Locally: a(t) a sin(m t) and m a = ⇢ ⇡ 0 a 2 a 0 DM I Jeff = ga 2 ⇢DMB sin(mat) p

Axion dark matter modiﬁes Maxwell’s equations

I Recall axions also couple to QED:

1 µ⌫ ↵EM = gaaFµ⌫F˜ ga L 4 / fa

Scott Thomas and Blas Cabrera (2010), Sikivie et. al. (2013) 1 2 2 I Locally: a(t) a sin(m t) and m a = ⇢ ⇡ 0 a 2 a 0 DM I Jeff = ga 2 ⇢DMB sin(mat) p

Axion dark matter modiﬁes Maxwell’s equations

I Recall axions also couple to QED:

1 µ⌫ ↵EM = gaaFµ⌫F˜ ga L 4 / fa

I Magnetoquasistatic approximation: new electric current that follows B-ﬁeld lines @a B = g B r⇥ a @t

Scott Thomas and Blas Cabrera (2010), Sikivie et. al. (2013) Axion dark matter modiﬁes Maxwell’s equations

I Recall axions also couple to QED:

1 µ⌫ ↵EM = gaaFµ⌫F˜ ga L 4 / fa

I Magnetoquasistatic approximation: new electric current that follows B-ﬁeld lines @a B = g B r⇥ a @t

1 2 2 I Locally: a(t) a sin(m t) and m a = ⇢ ⇡ 0 a 2 a 0 DM I Jeff = ga 2 ⇢DMB sin(mat) p

Scott Thomas and Blas Cabrera (2010), Sikivie et. al. (2013) Axion dark matter generates magnetic ﬂux

Superconducting pickup loop

R r a h B0 2 I Axion effective current: I R J eff ⇠ eff Ieff I B Rg 2 ⇢ B sin(m t) ⇠ R ⇠ a DM 0 a 16 22 I f = 10 GeV, Bp 5 T, R 4 m: B 10 T (KSVZ) a 0 ⇠ ⇠ ⇠

Axion dark matter generates magnetic ﬂux

Superconducting pickup loop

R r a h B0

I Estimate B-ﬁeld induced through pickup loop (r = a = h = R) Axion dark matter generates magnetic ﬂux

Superconducting pickup loop

R r a h B0

I Estimate B-ﬁeld induced through pickup loop (r = a = h = R) 2 I Axion effective current: I R J eff ⇠ eff Ieff I B Rg 2 ⇢ B sin(m t) ⇠ R ⇠ a DM 0 a 16 22 I f = 10 GeV, Bp 5 T, R 4 m: B 10 T (KSVZ) a 0 ⇠ ⇠ ⇠ Two readout strategies

Broadband Resonant M Δω M

L L i Lp L p C L R Li

Better at low frequency Better at high frequency Two readout strategies

Broadband Resonant pickup loop M Δω M

L SQUID L i Lp L p C L L R i Capacitors bring p resistance -> !res =1/ LC Thermal noise dominates Better at low frequency Better at high frequency Two readout strategies

Broadband Resonant pickup loop M Δω M

L L i Lp L p C L R Li SQUID noise dominates

Better at low frequency Better at high frequency I Scale to R 4 m 1/2 ⇡ 20 I S 5 10 T/pHz B ⇡ ⇥ I t =1year interrogation time for GUT scale axion 2 3 I Coherence time: ⌧ 2⇡/(mav ) 10 s(v 10 ) 1⇠/2 1/4 ⇠ 22 ⇠ I S/N =1for B = S (t⌧) 10 T B ⇠

Broadband estimate M

R Lp L

I Example from MRI application: (Myers et. al. 2007) 1/2 17 I B-ﬁeld sensitivity: S 6.4 10 T/pHz B ⇡ ⇥ I R 3.3 cm ⇡ I t =1year interrogation time for GUT scale axion 2 3 I Coherence time: ⌧ 2⇡/(mav ) 10 s(v 10 ) 1⇠/2 1/4 ⇠ 22 ⇠ I S/N =1for B = S (t⌧) 10 T B ⇠

Broadband estimate M

R Lp L

I Example from MRI application: (Myers et. al. 2007) 1/2 17 I B-ﬁeld sensitivity: S 6.4 10 T/pHz B ⇡ ⇥ I R 3.3 cm ⇡ I Scale to R 4 m 1/2 ⇡ 20 I S 5 10 T/pHz B ⇡ ⇥ 1/2 1/4 22 I S/N =1for B = S (t⌧) 10 T B ⇠

Broadband estimate M

R Lp L

I Example from MRI application: (Myers et. al. 2007) 1/2 17 I B-ﬁeld sensitivity: S 6.4 10 T/pHz B ⇡ ⇥ I R 3.3 cm ⇡ I Scale to R 4 m 1/2 ⇡ 20 I S 5 10 T/pHz B ⇡ ⇥ I t =1year interrogation time for GUT scale axion 2 3 I Coherence time: ⌧ 2⇡/(m v ) 10 s(v 10 ) ⇠ a ⇠ ⇠ Broadband estimate M

R Lp L

I Example from MRI application: (Myers et. al. 2007) 1/2 17 I B-ﬁeld sensitivity: S 6.4 10 T/pHz B ⇡ ⇥ I R 3.3 cm ⇡ I Scale to R 4 m 1/2 ⇡ 20 I S 5 10 T/pHz B ⇡ ⇥ I t =1year interrogation time for GUT scale axion 2 3 I Coherence time: ⌧ 2⇡/(mav ) 10 s(v 10 ) 1⇠/2 1/4 ⇠ 22 ⇠ I S/N =1for B = S (t⌧) 10 T B ⇠ Axion dark matter projected reach

t = 1 year Bmax =5T

Broadband R ~ 1 m T < 60 mK

R ~ 4 m Axion dark matter projected reach

t = 1 year Bmax =5T Resonant T = 10 mK, Broadband Q 106 R ~ 1 m ⇠ T < 60 mK

R ~ 4 m Axion dark matter projected reach

t = 1 year MQS approximation Bmax =5T breaks down Resonant T = 10 mK, Broadband Q 106 R ~ 1 m ⇠ T < 60 mK

R ~ 4 m Outline

I Axion particle physics (review)

I Axion cosmology (review)

I ABRACADABRA: Cosmic axion detection (theory)

I ABRACADABRA-10 cm at MIT (experiment) I Funded by the NSF (as of this week)

The MIT prototype: ABRACADABRA-10 cm

I ABRACADABRA: A Broadband/Resonant Approach to Cosmic Axion Detection with an Amplifying B-ﬁeld Ring Apparatus 2 I Dimensions: 12 12 cm (R =3cm, h = 12 cm), B =1T ⇥ I People (LNS+CTP, PSFC, +1 Princeton): Janet Conrad, Joe Formaggio, Sarah Heine, Yoni Kahn, Joe Minervini, Jonathan Ouellet, Kerstin Perez, Alexey Radovinsky, B.S., Jesse Thaler, Daniel Winklehner, Lindley Winslow I Lindley’s dilution refrigerator (< 100 mK) I Workable space: R 25 cm, h 25 cm ⇠ ⇠ The MIT prototype: ABRACADABRA-10 cm

Toroidal magnet coil

Thanks Daniel Winklehner for CAD model and slides. ABRA-10 cm: vertical cut

test wire ABRA-10 cm: pickup cylinder

Superconducting pickup cylinder

Pickup loop leads

Cut cylinder so current returns through leads ABRA-10 cm: reach after 1 month ABRACAD˚ ABRA˚

ÅBRACADÅBRA 4

MIT 5

081502 1X 081504

081503 1X 4X 081501 1X 1X 1 1X

2 2X 6 2X 4X 3 ! 1X 2X

ÅBRACADÅBRA Complementary proposals for axion dark matter experiments CASPEr:CASPEr: oscillating NMR neutron EDM detection [Budker et al., 1306.6089] a g2 i ¯ ˜µp⌫ 2⇢DM axion = ✓µ+ 2 Gµ⌫G gdaNLµ 5NF fa 32d⇡n = gd cos(mat) L 2 ✓ ◆ ma 16 2.4 10 e cm dn(t)=frequencygHzd a(t) ,gd ⇥ · 102 104 106 108 1010 1012 1014 ⇡ 4 fa resonance !4 New Force ! " 10 frequency Hz

2 4 6 8 10 12 14 10!6 10 10 10 10 10 10 10 Static EDM ! " sin [(2µBext ma)t] 10!8 SN 1987A M(t) npµE d sin(2µB t) 10!5 S n ext ⇡ 2µBext ma !10 " 10 1 SN 1987A !

!12 ADMX

GeV 10 ALP DM ! 10!10

aNN !14 " g 10 2 B ! SQUID ext !16

10 GeV ADMX ! QCD Axion pickup d M g !15 QCD Axion 10!18 10 loop 10!20 E ,v !14 !12 !10 !8 !6 !4 !2 0 10 10!20 10 10 10 10 10 10 10 mass eV Figure 6

CASPEr setup. The applied magnetic field B ext is colinear with the sample magnetization, M .In Figure 7 10!14 10!12 10!10 10!8 10!6 10!4 10CASPEr-Wind!2µ 100 the nuclear spins precess around the local velocity of the dark matter, v,whilein Sensitivity• of the CASPEr-Wind proposal. ALP parameter! " space in pseudoscalar coupling ofCASPEr-Electric axion the nuclear EDM causes the spins to precess around an eective electric field in Measures couplingmass eV to G µ G through nucleon spin to nucleons Eqn. 20 vs mass of ALP. The purple line is the region in which the QCD axionthe may crystal E ,perpendiculartoB ext.TheSQUIDpickuploopisarrangedtomeasurethe lie. The width of the purple band gives an approximation to the axion model-dependence in this FIG. 2: Estimated constraints in the ALP parameter space in the EDM coupling g (where the nucleontransverse EDM is magnetizationd = g a and of the sample. coupling.• The darker purple portion of the line shows the region in which thed QCD axion could be n d a is theMeasurement local value of the ALP field) vs. the ALP mass [17].taken The green region isin excluded external by the constraints on excess E cooling and B fields allof of supernova the dark 1987A matter [17]. and The have bluefa region

70), and is also well-motivated theoretically (24). 3Note that the Wind coupling leads to a spin-dependent force which could be probed using NMR techniques as well e.g. (80, 81, 82, 83, 84, 85, 86).

www.annualreviews.org Experimental Axion Searches 15 • Light bosonic dark matter future

I MIT: ABRA-10 cm followed by ABRA-1 m (B 10 T) ⇠

I ABRA-1 m: multiple experiments at different locations I Preliminary discussions with Korean Center for Axion and Precision Physics (Yannis Semertzidis)

I Axions and light bosonic dark matter well motivated by high-scale physics (e.g., compactiﬁed string theory)

I Detection may provide window to high-scale physics (GUT scale, inﬂation,...)

I New ideas to search for ultra-light scalars, dark-photons, etc. (laboratory experiments + astrophysics) I e.g., CASPEr experiment I Black Hole superradiance Questions? Axion Backup Slides 1 T P (!) dtB(t)sin(!t)=P0(!)+Pn(!) ⌘ pT Z0