Axion and Dark Matter Studies in IBS
Kiwoon Choi
The 3rd KMI International SymposiumJan. 6, 2017, Nagoya, JapanThe IBS Center for Theoretical Physics of the Universe

There are plenty of evidences for dark matter (DM) in the universe.

We know too little about DM, so theoretically there are so many
possible candidates for DM.

Baer et al ‘14

Which one would be the more likely candidate?
Axion and WIMP (Weakly Interacting Massive Particle) are the leading
candidates as they appear as a natural consequence of an attempt tosolve the naturalness problems in the Standard Model (SM) of particle physics.

Standard Model + General Relativity:* Three so different mass scales
Dark energy (= Cosmological constant):
Higgs boson mass:
Planck scale:* Two so different CP-odd angle
Kobayashi-Maskawa phase for the weak CP violation:

QCD vacuum angle which can cause strong CP violation:Naturalness problems
If something is so small compared to its cousin,
putting big and small together requires a fine tuning.
3 fine-tuning problems associated withthe 3 scales and 2 angles:* Cosmological constant problem:
Why ΛDE/MPlanck ~ 10-30 is so small?
* Gauge hierarchy problem:
Why mhiggs/MPlanck ~ 10-16 is so small?
* Strong CP problem:
Why θQCD /δKM < 10-10 is so small?
A. Weiler

Possible explanations for fine tuning
Anthropic selection
in multiverse?

Physical mechanism tomake the fine tuning natural?
Peccei-Quinn symmetry
with axion DM, …?

Cosmologicalconstantproblem

Strong CP problem

SUSY with WIMP DM, …?
Illustration by Villadoro

Gauge hierarchy problem
As the strong CP problem does not find a solution in multiverse, it ismore likely that there is some physical mechanism to make θQCD small,and the most appealing solution is the axion solution.

Axion solution to the strong CP problem
Introduce a spontaneously broken global U(1) symmetry, which is explicitly
broken mostly by the QCD anomaly (Peccei-Quinn symmetry ‘77)
 θQCD becomes a dynamical field “axion” being the Nambu-Goldstone bosonof the spontaneously broken PQ symmetry:

fa = Axion scale = Mass scale of the spontaneous breaking of U(1)PQ
Low energy QCD dynamics develops an axion potential minimized at <a >= 0:θQCD = a/fa

QCD becomes CP conserving
after the axion is settled down
at its VEV.

Most of axion physics is determined by the axion scale fa* axion mass:* axion-photon couplings:* axion-nucleon couplings:

Star cooling by axion emission: fa > 4 x108 GeVτa ≫ 1017 sec, so once axions were produced in the early universe,they constitute (part of) the DM in the present universe.

Cosmological production of the QCD axion dark matter
Misalignment

Topological defectsInitial axion field misaligned

axionic string attached by domain wallfrom the minimum of the axion potential0θQCD = a/fa
Kawasaki et al ‘14(if exists, the defect contribution dominates over the misalignment contribution!)
Axions from both misalignment and topological defects are produced whenma(t) ~ H(t), and subsequently evolve like non-relativistic matter, so their relicdensities have a common dependence on fa.

QCD axion has a good potential to be experimentally tested!
Axion dark matter
AstrophysicalboundIfaIIIII109

1010

1011

1012

1013

Axion
mediatedforce

Resonant cavity:

IIII

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1015

1016

1017

1018 (GeV)

IAXO:
Oscillating EDM induced
Next generation
by oscillating DM axions
of axion helioscope(Graham & Rajendran ‘13)

(Arvanitaki& Geraci ’14)

Dish antenna(Horns et al ‘12)

(Sikivie ‘83)

ABRACADABRA:
Effective current inducedby oscillating DM axions(Kahn, Safdi & Thaler ‘16)

Axion cosmology
Axion cosmology depends crucially on how the PQ symmetry is realized
during the early universe inflation.

Pre-inflation scenario:
PQ symmetry is spontaneously broken during the inflation epoch, andthe spontaneously broken phase is kept until today.

Post-inflation scenario:
There has been a phase of restored PQ symmetry after inflation, sothe last PQ phase transition from the restored phase to the spontaneously
broken phase took place after the inflation is over.

Pre-inflation scenario:
No axionic strings or domain walls, but the axion field could have a nonzero
misalignment together with a fluctuation generated during the inflation period:a/faRelic axion dark matter:

Preskill, Wise, Wilczek ‘83; Abbott , Sikivie ‘83; Dine, Fischler ’83; …

Axion isocurvature perturbation:

Axenides, Brandenberger, Turner ‘83; Fox, Pierce, Thomas ’04; …

Post-inflation scenario:
There are axionic strings attached by NDW domain walls, which would cause
cosmological domain wall problem unless NDW = 1:
Axionic string produced
during the PQ phase transition

Domain walls attached to strings, which are formed
during the QCD phase transition

To avoid the overclosure due to stable string-wall networks (=domain wallproblem), we need

Then the axion DM is mostly from the collapsing string-wall system, yielding
Davis ‘86; Davis, Harari, Sikivie ‘87;
Davis, Shellard ‘89; …

Axion dark matter

Pre-inflation:

Post-inflation

anthropicaxion DMKC, Jeong, Seo ‘14Any hint on axion scale from theory?
Axions in string theory
Extended objects in string theory predict antisymmetric tensor gauge fields
which couple to their world-volume:twith higher-dimensional gauge symmetry:
xUpon compactification, antisymmetric tensor field in extra-dimensional
directions can be identified as 4-dimensional pseudo-scalar axions:

6D internal space

* Axion scales determined by compactification
Compactification

gravity–axion unification
KC, Kim ’85; Svrcek, Witten ’06

Compactification should occur before the end of inflation, then the axion
cosmology follows the pre-inflation scenario with

Stringy axion DM withthe axion isocurvature perturbation:is severely constrained bywith
Stringy inflation scenario

Burgess, Cicoli, Quevedo ‘13r = tensor to scalar ratio in CMB= 0.16 (H/1014 GeV)2

 r < few x 10-11 which is difficult to be compatible with most ofthe known stringy inflation scenario

* Axion scale determined by SUSY breaking
KC, Jeong, Okumura, Yamaguchi ’11

Compactification

Stuckelberg mixing with an anomalousU(1)A gauge boson:

The stringy axion “a“ from antisymmetric tensor field is eaten by the U(1)Agauge boson, while leaving instead another axion which originates fromthe phase of U(1)A-charge complex scalar fieldTypically:in this scenario, so one should

follow again the pre-inflation scenario to avoid the domain wall problem.

Axion scale determined by SUSY breaking

KC, Jeong, Seo ‘14with,* LHC SUSY search: mSUSY > 1 TeV* mhiggs = 125 GeV: mSUSY < 104 - 107 TeV* Gauge coupling unification: mSUSY < 103 TeV

Arvanitaki et al’ 12* Isocurvature constraint on axion scale determined by SUSY breaking,

stringy inflation scenario

This scenario can be consistent with most of the known string inflation model.

Where is axion?
Axion dark matter
AstrophysicalboundAxion scale determinedby compactification

Axion scale determined
by SUSY breaking

IfaI

I

I

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1091010

1011

1012

1013

I

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II101510161017

1018 (GeV)DM studies in IBS

IBS includes 28 research centers for basic science(math, physics, chemistry, life science), and there arethree research centers related to DM physics:* Center for Theoretical Physics of the Universe (CTPU)* Center for Axions and Precision Physics (CAPP)* Center for Underground Physics (CUP)23

Center for Axion and Precision Physics (CAPP)
Projects : Search for axion dark matter, Detection of axion-mediated long range
forces, R&D for storage ring proton EDM experiment
Refurbishing a stateof the art lab inan existing bldg.

Members : 1 Director
 1 Group Leader
 ~25 Research Fellows
 2 Engineers
 6 Administrators
 ~15 Graduate Students

State of the art infra-structure:* 7 low vibration pits forparallel experiments* 6 high power dilution
refrigerators* high B-field magnets:
25T, 18T, 12T

Magnet schedule
2016

2017

2018

2019

2020

deliveryoperation
2021

2022

2023

BNL solenoid
25 T, 100 mm
Oxford solenoid
12 T, 320 mm
SuNAM solenoid
18 T, 70 mm
SuNAM solenoid
26 T, 25 mm
Small toroidal
magnet 12 T,R=500 mm, r=110mm• 26 T/25 mm solenoid : operation schedule?
• small toroidal magnet : depends on the starting point

2024

Expected axion mass range per magnet
locationmagnetFridge

C105

dry 8T/110mm

dry DFC105

dry 8T/155mm

dry DF

Pit3

wet 12T/180mm toroid

wet DF (need ~50 liters 3He)

Pit4

wet 9T/5inches

wet 3He

Pit5

wet 12T/320mm

wet DF (need ~50 liters 3He)

0.5~1.3 GHz

Pit6

wet 20T/65mm

dry DF

3~4 GHz

Pit7

wet 25T/100mm

dry DF

2~10 GHz

In few years, CAPP will override
the ADMX sensitivity, and explore
new territory with heavier axion mass:Search range

1~2 GHzAxions with ARIADNE:
Axion Resonant InterAction
DetectioN Experiment

Detection ofaxion-mediatedlong range force

27

Center for Underground Physics (CUP)

Projects : Search for WIMP-like dark matter (KIMS+),
Double Beta Decay (AMoRE), Low temperature Detectors.

Members : 1 Director
 2 Group Leaders ~25 Research Fellows
 6 Technicians 3 Administrators
 ~25 Adjunct Students.
Headquarter (2018-)

Yangyang underground laboratoryLabs.

Y2L-A5Y2L-A6

Current Daejeon Lab.

New underground lab. (2019-)

28

Projects at CUP1. COSINE-100 (Collaboration Of Sodium lodiNe Experiments)
 DM-ICE group + KIMS-NaI group  COSINE at Y2L.
 200 kg NaI(Tl) crystals inside liquid scintillator active veto.
 Phase I (100 kg) commissioned in Oct, 2016.  running stable.
 Develop purer crystals  Phase II exp. (2018-2019)
Expected Sensitivity for COSINE-100*Assumed 2 dru or 4 dru flat backgrounds depending on crystals.

2. AMoRE bb experiment

29

100Mo double beta decay experiment.

 Scintillating crystals at 10mK temperature.
 R&D for CaMoO4, Li2MoO4, Na2Mo2O7
 AMoRE-I :5kg crystals (2017-2018)
 AMoRE-II : 200 kg of (X)100MoO4 crystals. (2020-2022)
 Ultra-low background crystals are grown at CUP.

CaMoO4Na2Mo2O7

KamLAND-Zen 201630

3. NEOS (Neutrino Experiment for Oscillation at Short baseline ) Short baseline reactor neutrino experiment for sterile neutrino.
 Data taken for 6 months, with best signal to background ratio.
 Disfavored the best parameters from reactor anomaly with best limits fortheta 14 around ~ eV mass region.
 NEOS-II can be set at closer position at Russian reactor.

Conclusion The QCD axion, which was introduced originally to solve the strong
CP problem, is one of the most compelling candidate for dark matter,and may have a good chance to be discovered in near future.
 String theory provides the best theoretical framework to realize the axion
solution to the strong CP problem, and then there are two particularlyinteresting range of the axion scale suggested by string theory: The IBS Center for Axion and Precision Physics (CAPP) has an ambitious
plan to search for axion dark matter, which will have an enough sensitivity
to detect the axion dark matter witheven when the axions constitute only 10% of the observed DM.