First Result of NEOS Neutrino Experiment for Oscillation at Short - - PowerPoint PPT Presentation

▶
first result of neos
SMART_READER_LITE
LIVE PREVIEW

First Result of NEOS Neutrino Experiment for Oscillation at Short - - PowerPoint PPT Presentation

Aug 26, 2023 47 likes •262 views

First Result of NEOS Neutrino Experiment for Oscillation at Short baseline Kim Siyeon Chung-Ang University Seoul, Korea On behalf of NEOS Collaboration July 15, 2017 ICRC 2017, Busan 1 First Result of NEOS NEOS Publication Y. J. Ko

slide-1
SLIDE 1

First Result of NEOS

Neutrino Experiment for Oscillation at Short baseline

Kim Siyeon Chung-Ang University Seoul, Korea On behalf of NEOS Collaboration

July 15, 2017 ICRC 2017, Busan 1

slide-2
SLIDE 2

First Result of NEOS

  • NEOS Publication
  • Y. J. Ko et al., Sterile neutrino search at the NEOS experiment, Phys. Rev. Lett. 118(12),

121802 (2017)

  • Y. J. Ko et al., Comparison of fast neutrino rates for the NEOS experiment, J. Korean
  • Phys. Soc. 69(11), 1651 (2016)
  • B. R. Kim et al., Pulse shape discrimination capability of metal-loaded organic liquid

scintillators for a short-baseline reactor neutrino experiment, Phys. Scripta 90(5), 055302 (2015)

  • B. R. Kim et al., Development and mass production of a mixture of LAB- and DIN-

based gadolinium loaded liquid scintillator for the NEOS experiment, J. Radioanal.

  • Nucl. Chem. 310(1), 311 (2016)
  • More papers on analysis and instruments are in progress.
  • Collaborators: 20 in 7 institutes
  • (1) Joo, K., Kim, B.R., (2) Ko, Y.J., Jang, C.H., Jeon, (3) E. J., Kim, Y., Lee, J.,

Lee, J.Y., Oh, Y., Park, H.K., Park, K.S., (4) Han B., Sun, K.M., (5) Park, H., (6) Kim, H., Lee, J., (7) Kim, H.S., Kim, J., and Seo, K.M.

July 15, 2017 ICRC 2017, Busan 2

slide-3
SLIDE 3

NEOS: Motivation and Purpose

  • Reactor Anomalies
  • Flux deficit
  • 5-MeV excess

July 15, 2017 ICRC 2017, Busan 3 RENO Mention et al, 2011

slide-4
SLIDE 4

NEOS: Motivation and Purpose

  • Reactor Anomalies
  • Flux deficit
  • 5-MeV excess

July 15, 2017 ICRC 2017, Busan 4

  • T
  • scan the possibility of the existen

ce of a sterile neutrino of the mass ~1 eV

  • To analyze the spectral shape

(not the absolute rate) of react

  • r antineutrino

NEOS baseline 24 m

  • Single detector needs
  • an accurate reference reactor a

ntineutrino flux/spectrum

  • understanding the detector resp
  • nse is crucial, especially energ

y-charge relation

slide-5
SLIDE 5

Experiment Site:

July 15, 2017 ICRC 2017, Busan 5

Habit Nuclear Power Plant in Younggwang, Korea

  • 2.8-GWth commercial reactor
  • Core size: 3.1-m diameter and 3.8-m height
  • Low enriched Uranium fuel (4.6% 235U)

Detector in Tendon Gallery

  • ~24-m baseline and ~20-m.w

.e overburden

ICRC 2017

1

2

3

4 5 6

✦

slide-6
SLIDE 6

Sep '15 Nov '15 Jan '16 Mar '16 May '16

DAQ Livetime (%)

100 80 60 40 20

Neutrino runs Test/Calibration

  • 46 days’ reactor off data + 180 day’s reactor on data + calibration
  • stable reactor operation, ~90% DAQ efficiency

Livetime + IBD event rate

July 15, 2017 ICRC 2017, Busan 6

slide-7
SLIDE 7

Sep '15 Nov '15 Jan '16 Mar '16 May '16

DAQ Livetime (%)

100 80 60 40 20

Neutrino runs Test/Calibration

  • 46 days’ reactor off data + 180 day’s reactor on data + calibration
  • stable reactor operation, ~90% DAQ efficiency

July 15, 2017 ICRC 2017, Busan 7

Livetime + IBD event rate

slide-8
SLIDE 8

Active Reactor Core

  • 177 fuel rods, low enriched (4.65%) uranium-235 (LEU) fuel
  • Refueling by changing 1/3 of fuel rods for each burn-up cycle (~1.5 year)
  • Active core size: 3.1 m (φ), 3.8 m (h)

10000 15000

Burn-up [MTU/MWD]

5000

Fission Fraction

0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1

U-238

July 15, 2017 ICRC 2017, Busan 8

slide-9
SLIDE 9

Mean 23.64 Std Dev 0.8146 26

L [m]

22 23 24 25

p.d.f.

(20 m.w.e) 0

  • verburden

0.1 0.2 0.3 0.4 Mean S td Dev 23.64 0.8146

Detector Location / Baseline

~8 m NEOS Detector Active Core T endon Gallery Entrance / Exit

Neutrino travel distance distribution:

  • Beta decays uniformly generated in cyli

ndrical core

  • IBD interaction points uniformly distribut

ed in target

  • Distance-weighted effect: 1/L2

July 15, 2017 ICRC 2017, Busan 9

slide-10
SLIDE 10

July 15, 2017 ICRC 2017, Busan 10

Construction

slide-11
SLIDE 11
  • Homogeneous LS target

— 1008 L volume (R 51.5, H 121) cm — LAB+UG-F (9:1) — 0.5% Gd loaded for high neutr

  • n capture efficiency

— 38 8″ PMT in mineral oil buffer

  • Shieldings

— 10 cm B-PE (n), 10 cm Pb (γ) — active muon counter

  • Data AcQuisition

— 500 MS/s FADC (waveform) — 62.5 MS/s SADC (μ veto)

  • Source calibration through chi

mney

Linear Alkyl Benzene

5T PTFE reflectors

Detector Specification

July 15, 2017 ICRC 2017, Busan 11

slide-12
SLIDE 12

IBD Reconstruction

Selection rules developed for best S/N ratio:

  • Prompt energy: 1-10 MeV
  • Delayed energy: 4-10 MeV
  • Time coincidence: 1-30 μs
  • Multiplicity: no event before (after) 30 (150)

μs from the prompt/delayed pair

  • Muon veto: 150 μs
  • Pulse shape discrimination

30 40 50 60

Neutron Capture Time [µs]

10 20

Counts /day/0.8µs

50 100

Reactor ON Reactor OFF

7 8 9

Delayed Energy [MeV]

4 5 6

Counts /day/0.1MeV

20 60

Reactor ON Reactor OFF

40

4 5 6 7 8 9

Recontructed Energy [MeV]

1 2 3

Counts /sec/10keV

10−2 10−3 10−4 10−1 1

Target Single Events All: Reactor OFF All: Reactor ON Muon veto cut:Reactor OFF Muon veto cut:Reactor ON

July 15, 2017 ICRC 2017, Busan 12 S1+S2+background S2

slide-13
SLIDE 13

Pulse Shape Discrimination

  • IBD events vs. fast neutron’s scattering events
  • Qtail/Qtot or meantime of waveform.
  • LAB + DIN (UG-F) mixed LS.
  • More than 70 % of IBD background could be reduced after PSD.

5

p ( t )

psd

−10 −5 10 15 20

Events /day

10−1 1 10 102 Reactor OFF Reactor ON

Fast n e, γ

July 15, 2017 ICRC 2017, Busan 13

slide-14
SLIDE 14

Prompt Energy Spectrum

1 2 3 4 5 6

Prompt Energy [MeV]

  • Signal / Noise ~ 22
  • vs H-M: 5 MeV bump, not so practical to do the oscillation analysis
  • vs Daya Bay: bump not totally disappeared, fission fraction difference
  • Systematic uncertainties for the shape analysis:

reference spectrum > energy recon. >> background fluc., S2 cut efficiency …

7 ⋅ ⋅ 10

Events /day/100 keV

1.0

10

0.9

Systematic total

20 30 40 50 60

Data signal (Sneos=ON-OFF) Data background (OFF) MC no oscillation (Φhm⋅σ )

Vogel

MC no oscillation (Sdyb)

1 2 3 4 5 6 7 10

Prompt Energy [MeV] Data/Prediction

0.9 1.0 1.1 Sneos / MC(Φhm⋅

σ

) Systematic total

Vogel

4 5

Prompt Energy [MeV]

1 2 3 6 7 10

Data/Prediction

1.1

S / MC(S )

dyb neos

July 15, 2017 ICRC 2017, Busan 14

slide-15
SLIDE 15
  • c2 minima are found at

(sin22θ, Δm2)=(0.04, 1.3 eV2), (0.05, 1.73 eV2) with Δ c2 = c2 3n− c2 4n = 6.5.

  • p-value ~ 22%.
  • No strong sign of active-to-sterile

n oscillation.

Prompt Energy [MeV]

1 2 (2.32 eV2, 0.142) 3 4 5 6 7 ⋅ ⋅ 10

Data/Prediction

0.9

6000

1.0

4000

(1.73 eV2, 0.050) 1.1 NEOS/Daya Bay Systematic total

(c) July 15, 2017 ICRC 2017, Busan 15

3ν 4ν

χ2 -χ2

00 2 4 6 8 10 12 14

Entries (a.u.)

2000 8000 10000 MC pseudo-experiment no sterile neutrino. χ2 dist. (NDF=2)

Active-to-Sterile Oscillation

slide-16
SLIDE 16
  • Exclusion limits
  • Raster scan with c2 distribution
  • Exclude Δm2 < 3 eV2,
  • Rule out models, including RAA (reactor antine

utrino anomaly) and recent global analyses.

July 15, 2017 ICRC 2017, Busan 16

Active-to-Sterile Oscillation

slide-17
SLIDE 17

Thank you.

NEOS Collaboration

July 15, 2017 ICRC 2017, Busan 17

slide-18
SLIDE 18

Backup

July 15, 2017 ICRC 2017, Busan 18

slide-19
SLIDE 19

Non-Linear Charge Response to Energy

  • Signal quenched at low energy
  • Cerenkov light important at higher energy

Source position (Φ) target center (P) PMT (O) outside (Ch) calibraion chimney

4 5 6 7 8

True Gamma Energy [MeV]

1 2 3

Charge/Energy [pC/MeV]

450 500 550

PoBe(Ch)

137Cs(Φ) 40K(P) 60Co(Φ)

n-H(Φ) Tl(O)

208

PoBe(Ch)

NEOS Preliminary

@ Neutrino 2016

July 15, 2017 ICRC 2017, Busan 19

slide-20
SLIDE 20

NEOS status

  • NEOS is over due to regular maintenance of the tendon gallery (once every 5

years)

  • No strong evidence of oscillation from active-to-(~1 eV) sterile mixing.
  • T

endon gallery is a nice place for reactor neutrino experiment, but

  • Severe escaping γ effect with a small volume detecter without γ catcher.
  • Measurement of 1 whole burn-up cycle should help to understand the spectrum

in detail.

  • Rate analysis, Absolute spectrum,

235U

P1

239Pu 238U 241Pu

NEOS P2

21 July 15, 2017 ICRC 2017, Busan 20

slide-21
SLIDE 21

Dedicated room for neutrino experiments

ground level

active core experimental room (proposed)

NEOS @ tendon gallery Proposed new room core diameter 312.4 cm 365 cm core height 381 cm thermal power 2815 MW 3983 MW distance to core 24 m ~18 m *

  • verburden

>20 muon rate ~0.2 cm-2 min-1 * rectangular space (WxDxH m3) 4 x 2.5 x 3.3 8 x 5 x 4 * # of IBD events to be detected ( NEOS detector) ~2000 per day ~5000 per day *

July 15, 2017 ICRC 2017, Busan 21