Research Program towards Observation of e N Coherent Scattering - - PowerPoint PPT Presentation

Research Program towards Observation of

¯ νeN Coherent Scattering

¯ νeN

• .vb

Research Program towards Observation of ¯

νeN Coherent Scattering – p. 1/14

TEXONO Collabaration

Collaboration : Taiwan(AS, INER, KSNPS, NTU), China(IHEP, CIAE, THU, NJU), Turkey(METU), USA(UMD), India(BHU) Program : Low Energy Neutrino & Astroparticle Physics

28 m from Reactor core Kuo-Sheng Reactor Neutrino Laboratory

Research Program towards Observation of ¯

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Physics Programs

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1 10 10 2 10 3 10 4 10

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1 10 10

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ν

_ eN

ν

_ ee(SM)

ν

_ ee(MM)

Recoil Energy(keV) Count day-1 keV-1(1kg)

[3] [1] [2] [1] Magnetic Moment search at ∼ 10 keV range → Results published. [2] sin2θW measument at ∼ MeV range → Analysis under way. [3]

¯ νeN Coherent Scattering at sub keV range → Future goal.

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νeN Coherent Scattering – p. 3/14

¯ νe Magnetic Moment Search

1 kg HPGe detector at reactor 571/128 days ON/OFF data. Background level ∼ 1 cpd

µν < 7.2 × 10−11µB 90% C. L.

Low threshold (∼500 eV) detector

⇒ µν→2 × 10−11µB

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ref : [PRL 90 2003], hep-ex/0605006

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¯ νe at Low Energy

(dσ

dt )MM = πα2µ2

ν

m2

e ( 1

T − 1 Eν )

Low Energy → (dσ/dT)MM >> (dσ/dT)SM decouple bkg & unknown sources For T << Eν → dσ/dT depends on total flux φν NOT shape of φν(Eν)

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¯ νeN Coherent Scattering

ν + N → ν + N

(dσ

dt )SM = GF 2mN 4π

[Z(1 − 4sin2θW ) − N]2[1 − MNTN

2E2

ν ]

→ N2 enhancement Low recoil energy : ∼ 1.9 keV for Eν = 8 MeV, Ge

A fundamental neutrino interaction never been expermentally

• bserved.

A sensitive test to Standard Model. An important interaction/energy loss channel in astrophysics media. A promising new detection channel for neutrinos, without strict lower bound on Eν & the channel for WIMP direct detection. Involves new energy range at low energy, many experimental challenges & much room to look for scientific surprises.

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Quenching Factor

Quenching factor = 0.25, ∆E

E ∼ 0.05

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ν

_ eN q.f.=0.25

ν

_ eN q.f.=1.0

ν

_ ee(SM)

ν

_ ee(MM)

backgroud level Recoil Energy(keV) Count day-1 keV-1(5g, True flux)

Take Q. F. = 0.25, extrapolate background to eV level

⇒ signal/noise > 1 at 300 eV

At threshold ∼ 100 eV ⇒ 11 count day−1 kg−1

νN at accelerator ∼ 0.1 count day−1 kg−1 ¯ νeP(water) at KS ∼ 1 count day−1 kg−1

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ULE-HPGe detector

ULE-HPGe → developed for soft X-rays detection

→ easy & inexpensive & robust operation

threshold ∼100 eV achievable.

¯ νeN coherent scattering, CDM search, µν search.

Prototype detectors: 5 g, 4×5 g, 10 g, 20 g segmented. Scale-up ∼ 1 kg (segmented or multi-array).

5 g Detector 4×5 g Detector

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νeN Coherent Scattering – p. 8/14

Calibration & Threshold

Source : 55Fe(5.9 keV, 6.49 keV) and Ti(4.51 keV, 4.93 keV) :

eV

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count / 10 eV

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threshold ~ 100 eV

Using uncorrelated trigger as energy zero Extrapolate energy calibration to low energy

⇒ threshold ∼ 100-200 eV.

Need calibration in low energy to comfirm this!

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Yangyang Underground Lab.(Y2L), Korea

700 m of rock → Cosmic-rays level 5 order less. 5 g ULE-HPGe. Study background and feasibility for CDM searches. may evolve into a full-scale (∼1 kg) CDM experiment.

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Background Measurement at KS Lab. & Y2L

keV

1 10

count /day /keV /kg

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KS - 5 g KS - 4x5 g Y2L - 5 g KS - 1 kg

KS Lab. & Y2L : same background level for 5 g detector. Background level different for 1 kg & 5 g detector

→ self-shielding → reproduced in simulations.

Intensive studies of sub-keV background under way.

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νeN Coherent Scattering – p. 11/14

R&D Program towards Realistic Size

O(1 kg) for ¯

νeN & CDM experiments.

sub-keV background study at power plant & underground lab. design of active & passive shielding based on this. compare performance of various prototypes. devise calibration scheme at sub-keV range. measure quenching factor of Ge with neutron beam. develop advanced PSD techniques to further suppress noise edge reduce threshold studying scale-up options ULEGe-detector Discrete elements Vs segmented Ge dual readout channels to suppress electronic noise

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νeN Coherent Scattering – p. 12/14

A Possible Design

3×3×5 elements, 20 g each (900 g). Dual readout per element. Outer layer as Veto. Gamma background suppress ∼ 1/100.

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Summary

Kuo-Sheng Neutrino Lab. : Established & Operational Unique HPGe Low Energy Data Background level ∼1 cpd

→ comparable to underground Dark Matter experiment.

Results on µν : Other Program under way. Future physics goal : get to ∼100 eV threshold.

¯ νeN coherent scattering experiment.

Dark Matter experiment. Improve µν search at threshold ∼500 eV. R & D Program : Optimise prototype ULE-HPGe. Background study at 100 eV - 1 keV. Study Scale-up options.

Research Program towards Observation of ¯

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