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Searching for Axions in CUORE

Sachinthya Wagaarachchi290E Seminar

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Introduction

● Dark Matter landscape● Axions

What are they, why and how to detect them.● CUORE

– DetectorHistory, Technique and How it achieves low background.

– Results and ProspectsCUORECINO DM results, CUORE prospects

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Ancient History...

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Ancient History...

From Surjeet's talk last month...

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Dark Matter - WIMPS

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Dark Matter - WIMPS

10-9 [eV/c2]

Axionsm

a~10-6 eV – 10-2 eV

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Continue...

● Dark Matter landscape● Axions

What are they, why and how to detect them.● CUORE

– DetectorHistory, Technique and How it achieves low background.

– Results and ProspectsCUORECINO DM results, CUORE prospects

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Axions

● What is an Axion?● A pseudo scalar particle● Appeared with the Pecci-Quinn solution to strong CP problem

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Axions

● What is an Axion?● A pseudo scalar particle● Appeared with the Pecci-Quinn solution to strong CP problem

● What is Strong CP problem?

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Axions

● What is an Axion?● A pseudo scalar particle● Appeared with the Pecci-Quinn solution to strong CP problem

● What is Strong CP problem– CP is violated in weak interactions.

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Axions

● What is an Axion?● A pseudo scalar particle● Appeared with the Pecci-Quinn solution to strong CP problem

● What is Strong CP problem– CP is violated in weak interation– Then why doesn't the strong interaction violate CP?

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Axions

● What is an Axion?● A pseudo scalar particle● Appeared with the Pecci-Quinn solution to strong CP problem

● What is Strong CP problem– CP is violated in weak interation– Then why doesn't the strong interaction violate CP?– It should!

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Strong CP Problem

● CP Violating term in QCD

● But no CP violation detected● Neutron electric dipole moment measurements → θ < 10-9

● Why so small?

● Strong CP Problem● Why CP conserved (θ ~ 0)?

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Strong CP Problem

● Peccei-Quinn Solution

● Apparently,● a(x) – the Axion fied

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Strong CP Problem

● Peccei-Quinn Solution

● Apparently,● a(x) – the Axion fied● The above Peccei-Quinn-Weinberg-Wilzcek axion was ruled out,● But Invisible Axion models are possible.● Bonus: It was not “invented” to solve the problem of dark

matter

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Axions – Where to find

● Solar Axions– Conversion of photons to axions in solar core– Average Eee = 4.2 keV– 57Fe M1 line at 14.4 keV

● Direct detection– Axion creation and detection in the lab

● Axion Wind– Detection by coherant interactions with matter (rotation of

spin, dipole moment) ← Surjeet's talk

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Axions – How to Detect

● Main interaction:– Axion - 2γ vertex

● Axion detecion using strong static magnetic fields– CAST, Tokyo, ADMX

● Primacoff coherant conversion in strong E fields in crystals– Axio-electric effect– Detect the X-ray

● Enhanced by bragg scattering

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Solar Axions – Detection by Bragg scattering

● The wavelength of axions matches the distance between crystal layers

● Can give up to 104 enhancement due to interference

dsinθθd

Crystal planes

γ's from axion conversion

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Introduction

● Dark Matter landscape● Axions

What are they, why and how to detect them.● CUORE

– DetectorHistory, Technique and How it achieves low background.

– Results and ProspectsCUORECINO DM results, CUORE prospects

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CUORECryogenic Underground Observatory for Rare Events

● Main Goal: 0νββ– Low Backgound → Possibility to pursue DM searches

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CUORE – Bolometric technique

Crystal Absorber (TeO2): E → ΔT Biased T sensor (NTD-Ge): ΔT → ΔV Thermal link (PTFE+gold wires): T0~10 mK

Particle energy is converted into phononsby dielectric and diamagnetic absorbers

whose heat capacity (C∝T3) is very low at low T. (At T~10 mK DT ~300 mK @ 1 MeV)

ΔT=E

C (T )

Δt=CG

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CUORE Underground

● Average Depth: ~1400m of rock● Water Equivalent: 3650 m● Reduces mu flux by a factor of

106

Located in the Gran Sasso National Lab, Italy.

In Hall A, (Same hall as CRESST and GERDA)

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CUORE Program

MiDBD1.8 kg 130Te

1997-2001

Cuoricino11.3 kg 130Te

2003-2009

T1/20ν > 2.8 x 1024 y T1/2

0ν > 2.1 x 1023 y

2013-2015 Begin 2016

CUORE-010.9 kg 130Te

CUORE209 kg 130Te

T1/20ν > 4.0x 1024 y

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CUORE● 19 Towers, 988 TeO2 Crystals. 5x5x5cm each● Total Active Mass: 741kg (~200kg 130Te)● Energy resolution: 5keV @2615 keV (FWHM)● Background Aim: 10-2 counts/keV/kg/year

Detectors

CUORE - 0● One Tower of 52 130Te Crystals. 5x5x5cm3 each● Total Active Mass: 39kg TeO2 (~11kg 130Te)● Energy resolution: 5keV @2615 keV (FWHM)● Background: ~0.06 counts/keV/kg/year

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PET+Boric acid shield

Internal lead shields

External lead shield

CUORE – Low background

● Rock Overburden● Lead Shields● Cleaned supports, plates etc● Radon pure working environment

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CUORE - Physics

208Tl

Cuorecino CUORE-0

0vbb Half life 2.8x1024 yr 2.7x1024 yr

Combined with Cuorecino 4.0x1024 yr

Resolution 5.8keV 4.9keV

Selection Efficiency ~83% ~81.3%

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CUORE – Low Energy Prospects

● WIMP Searches– Annual modulation (Bonus: Same place as DAMA)

● Axions – 57Fe M1 transition using Axio-electric effect– Using enhancement due to brag scattering

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CUORE – Low energy

● CCVR Runs (CUORE Crystal Validation Runs)– To test the performance of TeO2 production

– 4 TeO2 bolometers, 2 with heaters

● Lowering the threshold– Harder to distinguish between signal and noise– Pulse shape cuts

Vibration Event Signal Event

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CCVR – Noise reduction

Noise Events

Signal Events

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+ Heater events+ Particle MC events+ Heater MC events

Low Energy Threshold

● Cuorecino energy threshold ~tens of keV● CUORE-0 → Higher noise, mainly due to the old Cuorecino cryostat (Work in Progress)● CCVR2 – 3 channels with ← 3 keV threshold● CUORE – 3 keV achievable

Crystal Threshold (keV)

1 10.0

2 3.0

3 2.5

4 2.5

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14.4 keV Line?

● Calibrated using two peaks– 4.7 keV – Origin uncertain– 30.5 keV 121Te K shell de-excitation

● Good resolution– ~0.29 keV @4.7keV– ~0.33 keV @30.5 keV

● Background– ~25 counts/day/kg/keV

fa > 3.2x105 GeV (DFSZ Model)

fa > 2.41x104 GeV (KSVZ Model)

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CUORE – Low Energy Prospects

● WIMP Searches– Annual modulation (Bonus: Same place as DAMA)

● Axions – 57Fe M1 transition using Axio-electric effect– Using enhancement due to brag scattering

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CUORE – Bragg enhanced Axion search

● Known crystal orientation● Low background and threshold● Time variation of signal due to rotation of

earth● Comparable background rates to what's

required.

a b

Theoretical calculationFor gaγγ = 108 GeV-1 in TeO2

a. 5 keV < Eee < 7keVb. 7 keV < Eee < 7 keV

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Conclusion

● Axion is a very attractive candidate– As dark matter and other problems

● Few ways to detect, – All have to be ultra low background

● CUORE– 0νββ → ultra low background– Possibility detect DM – low threshold– Sensitivity enhanced by bragg scattering