Neutrino and Dark Matter Physics with Low Threshold Germanium Detectors

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Neutrino and Dark Matter Physics with Low Threshold Germanium Detectors

 Overview : TEXONO Program/Facilities

 Neutrino Physics at KSNL

 New Facility CJPL & CDEX Dark Matter

 Prospects & Perspectives

Henry T. Wong / 王子敬 Academia Sinica / 中央研究院

November 2017

@

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TEXONO-CDEX Collaboration

TEXONO

^[since 1997]

:

 Neutrino Physics at Kuo-Sheng Reactor Neutrino Laboratory (KSNL)

 Taiwan (AS, INER, KSNPS,NTU,NDHU)

 India (BHU)

 Turkey (METU,DEU)

CDEX

[birth 2009]

:

 Dark Matter Searches at China Jin-Ping Underground Laboratory (CJPL)

 China (THU, CIAE, NKU, SCU,YLJHD)

Taiwan EXperiment On NeutrinO

China Dark Matter EXperiment

 Research Program:

Low Energy Neutrino and Dark Matter Physics

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NCTS ECP (2015+)

 ν-NSI ; BSM ν-e & ν-N ;

 Atomic/nuclear effects in ν/χ interactions ;

 ν/χ – em effects ;

 ν-N QM coherency effects ;

 Sterile-ν DM ; dark photons ;

 ……

TEXONO Theory Program

[AS, NTU, NDHU, DEU(Turkey), SCU(China) …… ]

C.P. Liu (NDHU)

J.W. Chen (NTU)

 Connections: Studies of EW/BSM physics involves exquisite understanding of the detection physics mechanisms which require state-of-the-art command of atomic, nuclear & QCD physics.

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4

• 28 m from core#1 @ 2.9 GW

• Shallow site : ~30 mwe overburden

• ~10 m below ground level

Kuo Sheng Reactor Neutrino Laboratory [KSNL]

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無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無無

Configuration:

Modest yet Unique

Flexible Design:

Allows different detectors conf. for different physics

Inner Target Volume

Front View (cosmic vetos,

shieldings, control room …..)

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ULB-HPGe [1 kg] CsI(Tl) [200 kg]

Multi-Disks Array [~300 Tb]

KSNL : Detectors Schematics

Sub-keV Ge Detectors (20-900 g)

Data Acquisition with FADC Readout & FPGA Capabilities

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Neutrino Properties & Interactions at Reactor

quality Detector requirements mass

Threshold ~ 100 eV

Observable Spectra with Reactor Neutrino “Beam”

Magnetic Moments

[PRL03,PRD05,PRD07]

 1 kg HPGe

ν-e Scattering SM ^[PRD10]

& NSI/BSM

[PRD10,PRD12,PRD15,PRD17]

 200 kg CsI(Tl)

νN Coherent Scattering [Current Theme;PRD16]

 sub-keV O(kg) ULEGe / PCGe

 Dark Matter Searches @ KSNL [PRD09,PRL13,AP14]

 CDEX Program@CJPL [PRD13,PRD14,PRD14;PRD16,PRD17]

 Theory Program

Neutrino Milli-charge ^[PRD14]

 sub-keV O(kg) ULEGe / PCGe

Reactor Neutrino Spectrum

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CsI(Tl) 200 kg :

Probe Electroweak Physics

^[PRD10]

RSM

sys stat

R =[1.08±0.21( )±0.16( )]×

) ( 024 . 0 ) (

031 . 0 251 . 0

sin²θ_W = ± stat ± sys

Verify SM Destructive Interference

⊕ Constraints on Various Beyond SM Effects [PRD10;PRD12;PRD15] 0

ON-BKG

200 kg CsI(Tl)

Best Measurement !

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Neutrino Electromagnetic Properties : Magnetic Moments

Search of µ

ν

at low enery with Reactor νe scattering

⇒ high signal rate & robustness:

 µ_ν>>SM [ decouple irreducible bkg ⊕ unknown sources ]

 T << Eν ⇒ dσ/dT depends on total φν flux but NOT spectral shape [ flux well known : ~6 fission-ν ⊕ ~1.2

238U capture-ν per fission ]

2

1 1

)

(

²

µ

_ν

πα ν σ ν

µ

 

 

= m T − E

dT e d

e

µ_ν(ν_e) < 7.2 X 10^-11 µ_B [PRL03,PRL07]

……. Same approach continuing in GEMMA (Kalinin, Russia)

µ_ν(ν_e) < 2.9 X 10^-11 µ_B [2013]

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Neutrino “Milli-charge”

[+ Theorists: Chen, Liu, Chi; PRD14]

 Identify New Twist - Cross-section enhanced at low energy transfer (“minimum ionizing”)

 Smoking-gun signatures for positive signals:

peaks at known K/L binding energy at known ratios [different from cosmic- activation electron-capture background]

 Present Bound : δ_Q < 10^-12

 Future Sensitivity Goal (100 eVee threshold): δ_Q ~ 10^-14

Neutrino

Electromagnetic Form Factors

Atomic Ionization Differential Cross-Section

with full atomic physics many-body “MCRRPA” calculation [PL13]

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Non-Relativistic Massive Sterile Neutrino to Light SM Neutrinos Via Transition Magnetic Moment Atomic Ionization

^[PRD16]

 Pole structure at differential cross-section at m

ν

/2 (q

²

~0)

Direct Search of Sterile Neutrinos as Dark Matter

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Current Research Theme:

“sub-keV” Ge Detectors

 Physics Goals for O[100 eV threhold ⊕ 1 kg mass ⊕ 1 cpkkd] detector :

 νN coherent scattering , potential applications to reactor monitoring

 Low-mass WIMP searches [CDEX Program @CJPL]

 Explore ν/WIMP electromagnetic properties &

interactions

 Open & Explore new detector window & detection

channel & physics parameter space

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p- PCGe

[500g – 1 kg]

p⁺

n⁺(~1mm Li diffused)

n- PCGe

[500 g]

n

⁺

p

⁺^(~0.5μm Boron implanted) ^{500 g}

4x5g ULEGe

Baseline Hardware Design

[Both TEXONO@KSNL & CDEX-1@CJPL]

Electro-Cooled p-PCGe^{[1430 g]}

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Neutrino-Nucleus Coherent Scattering :

 Standard Model allowed and predicted processes :

ν (χ)

 Neutral current process (same for all ν-flavor)

 σ ∝ N² @ E_ν < 50 MeV

⇒ “Coherent” [probe “sees” the whole nucleus]

 sensitive probe for BSM ; interest in reactor monitoring

 important process in stellar collapse & supernova explosion

 analogous interaction used in dark matter detection

 Ge at KSNL @ QF~0.2 : cut-off ~ 300 eV ;

Rate _{~10 kg}^-1 _day^-1_@ threshold~100 eVee

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 Partial Coherent νN Elastic Scattering Observed by COHERENT@ORNL, ν @ π-DAR

(Science-2017)

!

Complementarity (Extensions) of Reactor Neutrinos:

 Different kinematics regimes : q²0 ; FF(q²)=1

 Full QM Coherency [DAR-νN @ ~0.6 - 0.7 for CsI , threshold 4 keVnr]

 Sensitive to different BSM/NSI (e.g. photon-like massless mediator)

 Interest in Potential Applications to reactor monitoring

<φ> : averaged decoherence angle.

Coherency in Neutrino-Nucleus Elastic Scattering

[PRD16]

 Quantify transitions between Coherency & Decoherency

 Complementarity between different Sources & Target

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Standard Model Cross-Sections at KSNL

[ with Quenching Function for Ge for nuclear recoils ]

 Needs Background < 10 cpkkd, Target 1 cpkkd

 Needs Threshold < 200 eV_ee, Target  100 eV_ee

Current Focus !!

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 Merits: 2400+ m rock overburden ; drive-in road tunnel access ; superb supporting infrastructures

 Operated & Managed by THU & YLRHDC

 CJPL-I (2010): 6X6X40 m cavern

 CJPL-II (2017-18) : [ 4X(14X14X130 m) Halls ] + Pits

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~2400 m

~9000 m

Physics Today September 2010

6 m (H) X 6 m (W) X 40 m (L)

CDEX-

TEXONO PandaX

Starting with plans &

sketches ….

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CDEX-1 @ CJPL-I

Threshold (published results): 450 eVee

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CDEX-1 Results on χN SI/SD ; solar & DM Axions

leading sensitivities

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CJPL-Phase II

 ~500m west to CJPL-1

 Construction started 2014

 Rock Excavation completed May 2016

 To be Commissioned Soon…

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CJPL-II Layout

 Four **14m14m130m Main Halls**

 Two Pits: (1) 18( φ )X18(H)m ; (2) 27(L)X16(w)X14(D)m

 Total space: ~300K m³

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CJPL-II Civil Engineering

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Plan of Ground Laboratory (~2020)

 offices, workshops, meeting venues, accommodation,

logistics (~150 people)

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CDEX-1T (HPGe DM & 0νββ) Projects

CJPL-II Hall-C Pit

(Foreseen)

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

Towards Ton-scale enriched-Ge76 experiment for neutrinoless double beta decay experiment to cover the “Inverted Hierarchy”



Cast : mainly GERDA, Majorana, CDEX groups



CDEX group – build a case of hosting this experiment at CJPL-II



Great Opportunities (Expensive Problems) in Nuclear Physics –

nuclear matrix elements, g_A in nuclear process…….

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