: A QCD AXION DIRECT- DETECTION EXPERIMENT XIAOYUE LI FOR THE MADMAX COLLABORATION MAX PLANCK INSTITUTE FOR PHYSICS, MUNICH, GERMANY TAUP Toyama, September 9, 2019
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 2 INTRODUCTION 09.09.2019 THE STRONG CP PROBLEM ▸ The QCD Lagrangian contains a CP-violating term: ℒ QCD = . . . + α s ¯ ¯ θ G μν a ˜ G μν a , θ = θ QCD + θ Yukawa ∈ [ − π , π ] ∼ 𝒫 (1) 8 π ▸ Neutron electric dipole moment d N ∼ 10 − 16 ¯ θ e -cm < 3 × 10 − 26 e -cm ⇒ ¯ θ < 3 × 10 − 10 ▸ The Standard Model does not provide a reason for why is so ¯ θ tiny, i.e. the strong CP problem. ▸ The Peccei-Quinn mechanism provides a reason for the value of ¯ θ and predicts a light neutral pseudoscalar boson — the axion.
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 3 INTRODUCTION 09.09.2019 THE PECCEI-QUINN MECHANISM ▸ Peccei-Quinn introduces a global U(1) PQ symmetry which spontaneously breaks at T = f a ≫ Λ QCD 1 GeV < T < f a (PQ symmetry breaking) T < 1 GeV (QCD phase transition) θ α s α s a + 1 2 ∂ μ a ∂ μ a + a QCD ▸ ℒ = . . . + ¯ 8 π G μν a ˜ G μν 8 π G μν a ˜ G μν V ( θ ) a f a θ + a Axion potential is minimized at ▸ ¯ V a ( a / f a ) = 0 θ ( = a ) f a f a The axions produced by the “misalignment” ▸ Measured today mechanism are a good CDM candidate
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 4 INTRODUCTION 09.09.2019 CONSTRAINTS ON QCD AXION MASS Λ 2 ∼ 5.70 μ eV 10 12 GeV QCD ∼ f a f a
Xiaoyue Li (MPP Munich) Scenario A: PQ symmetry breaking TAUP 2019 Toyama � 5 INTRODUCTION 09.09.2019 happens before inflation CONSTRAINTS ON QCD AXION MASS Scenario B: PQ symmetry breaking happens after inflation
� Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 6 AXION DETECTION 09.09.2019 CDM AXION DIRECT-DETECTION ▸ Axion-photon interaction: α aF μν ˜ ℒ a γγ = C a γγ F μν Model-dependent and of order 1 2 π f a g a γ = 2.04(3) × 10 − 16 GeV − 1 m a μ eV C a γγ ▸ CDM axions behave like a classical wave : � a / f a = θ = θ 0 cos( m a t ) ▸ E.g. � m a ∼ 100 μ eV , local galactic axion density ρ a = 0.3 GeV/cm 3 λ a = 2 π ▸ Axion de Broglie wavelength: � ≳ 10 m ( v a ≈ 10 − 3 c ) m a v a ▸ Axion phase-space occupancy: � 𝒪 a ∼ n a λ 3 a = ( ρ a / m a ) λ 3 a ∼ 10 22 g a γ a ▸ Axion-Maxwell equation under external B-field : � ∇ ⋅ D = ρ f − g a γ B e ⋅ ∇ a { ∇ × H − · D = J f + g a γ B e · a ~ B
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 7 AXION DETECTION 09.09.2019 AXION HALOSCOPE scaled fi eld strength a E x a = a 0 cos( m a t ) Local axion DM density ▸ Axion induced electric field: 1/2 C a γγ 300 MeV/cm 3 ) = 1.3 × 10 − 12 Vm − 1 × ( 10 T ) ( g a γ B e B e ρ a | E a | = − a ϵ ϵ Dielectric constant
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 8 AXION DETECTION 09.09.2019 CAVITY AXION SEARCH Resonant Cavity scaled Axion linewidth fi eld Δ ν a ∼ 10 − 6 ν strength a E x a = θ 0 cos( m a t ) Cavity linewidth P sig ∼ 1.9 × 10 − 22 W ( 2 0.4 ) ( 0.97 ) 2 0.45 GeV cm − 3 ) ( C a γγ 136 l ) ( 6.8 T ) ( ( 650 MHz ) ( 50,000 ) B e ρ a V C f Q Cavity volume, Cavity mode Cavity Quality factor factor scaled by � f − 3 ▸ At higher frequencies, cavities are increasingly difficult to build
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 9 AXION DETECTION 09.09.2019 HIGHER FREQUENCY: DIELECTRIC HALOSCOPE electromag. wave emission scaled fi eld strength a E x ▸ Power emitted at a metal ( � ) surface: ϵ = inf = 2 . 2 × 10 − 27 W 2 P sig m 2 ( 10 T ) B e C 2 a γγ A
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama 11 AXION DETECTION 09.09.2019 DIELECTRIC HALOSCOPE L ≪ λ deBroglie L ▸ Power enhancement from coherent emission from and resonance at interfaces Boost factor needs to be = 2.2 × 10 − 27 W 2 - Of order 10 4 ~10 5 P sig m 2 ( 10 T ) B e C 2 a γγ ⋅ β 2 - Frequency and bandwidth-tunable A
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama 12 AXION DETECTION 09.09.2019 β 2 BOOST FACTOR Power boost factor simulation (1D) ▸ � is roughly proportional to the number of β 2 Disc positions randomly varied by σ = 15 μ m discs 10 4 ∼ 10 5 ▸ � achievable with 80 discs with dielectric constant � ϵ ≈ 24 Power boost factor β 2 ∫ β 2 d ν = const ▸ Area law: � Frequency is tuned by changing disc positions
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 12 AXION DETECTION 09.09.2019 β 2 BOOST FACTOR : 3D EFFECTS Simulated power boost factor Simulated axion beam shape 1D model 3D total 3D coupled to antenna ▸ 3D simulation shows the axion beam shape is well matched to a Gaussian beam. ▸ Reduction and frequency shift of power boost factor relative to 1D prediction are expected; axion signal coupling to antenna also results in loss of received power.
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 13 AXION DETECTION 09.09.2019 β 2 BOOST FACTOR : 3D EFFECTS Simulated � w/ disc tilting Simulated � w/ disc surface roughness β 2 β 2 1 milirad 0.3 milirad 0.1 milirad ▸ Other 3D effects such as disc tilting, surface roughness and axion velocity have been studied. Requirements (tiling < 0.1 mili radian, surface roughness < 10 µm) can be satisfied experimentally.
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 14 MADMAX 09.09.2019 MAgnetized Disc and Mirror Axion eXperiment (MADMAX) MADMAX baseline design Booster with a mirror and 80 LaAlO 3 discs 1mm-thick, 1m 2 in area Receiver Mirror Cryostats chain B-field 9 T superconducting magnet with >1 2m m 2 aperture, <5% inhomogeneity Horn antenna Focusing mirror
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 15 MADMAX 09.09.2019 MADMAX SENSITIVITY Post-inflationary scenario Prototype detector sensitivity 5 years uninterrupted running QCD axion model benchmark β 2 = 5 × 10 4 * System temperature ~8K, �
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 16 MADMAX 09.09.2019 TIMELINE 2017-2019 2019-2022 2022-2025 2025-2035 DESIGN PROTOTYPING DETECTOR CONSTRUCTION DATA TAKING @ DESY HERA hall north MORPURGO magnet up to 1.9 T DESY MADMAX white paper First physics run at CERN with prototype detector Eur. Phys. J. C (2019) 79: 186 *Full-size detector
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 17 MADMAX R&D 09.09.2019 RECEIVER CHAIN Low-noise cryogenic amplifier T rec ≈ 5 − 6 K <2% deadtime Front-end mixers & amps Fake axion Samplers signal injection � 1.2 × 10 − 22 W signal detectable with ~days of measurement time LHe bath
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 18 MADMAX R&D 09.09.2019 PROOF-OF-PRINCIPLE BOOSTER ▸ Boost factor cannot be measured directly; it has to be calculated based on disc positions ▸ Disc positions can be obtained through the group delay of the reflectivity measurement ▸ precision achieved with up to 5 discs ∼ μ m ▸ Booster temporal stability, disc tilting effects etc. have also been studied 20cm sapphire discs
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 19 MADMAX R&D 09.09.2019 DIELECTRIC DISC ▸ Discs are � m in diameter and 1mm in 1.25 thickness ▸ Candidate material: LaAlO 3 ▸ ϵ ≈ 24 ▸ tan δ ≲ 10 − 4 ▸ Only grown on 3” wafer; tiling needed for 1 m 2 discs ▸ Material electromagnetic properties ( � , � ) at ϵ tan δ � GHz are under investigation f > 10 ▸ Other possible candidate materials are being explored First tiled LaAlO 3 disc ( 30 cm) ϕ =
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 20 MADMAX PROTOTYPE 09.09.2019 Preliminary prototype PROTOTYPE DETECTOR booster mechanics design 1 ▸ Aim to construct and commission prototype booster by 2022 ▸ 20 LaAlO 3 tiled discs with 30cm diameter; laser interferometer incorporated Preliminary prototype booster mechanics design 2 ▸ Hammer out the details of the mechanical design for the full- size detector ▸ First physics results in 2022 with Morpurgo magnet at CERN ▸ Development and testing of piezo motors are ongoing ▸ 4K, ~9T, long travel range, 6 kg load bearing, � m precision < 10 μ
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 21 MADMAX MAGNET 09.09.2019 MAGNET DESIGN STUDIES B 2 ⋅ T = 100 T 2 m 2 ▸ magnet has never been built before ▸ Working with innovation partners and an expert committee ▸ NbTi coil, 9 T field, 1.25 m 2 aperture, ~5% inhomogeneity ▸ Design to be finalized in 2019; demonstrator coil to be delivered by 2021; full magnet to be commissioned by 2025
Xiaoyue Li (MPP Munich) TAUP 2019 Toyama � 22 SUMMARY 09.09.2019 SUMMARY AND FUTURE PROSPECT ▸ There is a strong theoretical motivation for axion as it can solve the Strong CP problem and at the same time be a good CDM candidate ▸ The MADMAX experiment aims to search for QCD axion in the well-motivated mass range of � 40 ∼ 400 μ eV ▸ Novel dielectric haloscope to boost axion signal to a detectable level ▸ Design R&D and simulation studies are on going ▸ Prototype booster to be delivered by 2022 ▸ Aim for data-taking with full-size detector in 2025 Thank you for your attention
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