Current results of Neutrino-4 experiment with full-scale detector - - PowerPoint PPT Presentation

Current results of Neutrino-4 experiment with full-scale detector

Serebrov A.P., Samoilov R.M.

Collaboration Neutrino-4:

• 1. NRC “KI” Petersburg Nuclear Physics Institute, Gatchina,
• 2. NRC “Kurchatov institute”, Moscow,
• 3. JSC “SSC RIAR”, Dimitrovgrad, Russia
• 4. DETI MEPhI, Dimitrovgrad, 433511 Russia

International Workshop on Particle Physics at Neutron Sources 2018, Institut Laue-Langevin, Grenoble, France

Reactor antineutrino anomaly

• The reason of deficit

could be oscillation

• C. Giunti INFN

2 2 m [eV ]L[m] 2 2 14 P( ) 1 sin 2 sin (1.27 ) e e 14 E [MeV]           

SM-3 research reactor

• 100 MW thermal power
• Compact core 42x42x35cm
• Highly enriched 235U fuel
• Separated rooms for

experimental setup

• Rooms poorly protected from

space radiation

Vertical and horizontal sections of SM-3 reactor

Reactor SM-3

Week protection from cosmic rays (3-5 m w. e.)

Neutrino laboratory at SM-3 reactor

Gamma background (NaI detector)

0.001 0.01 0.1 1 10 1000 2000 3000 4000 5000 6000 I, s-1 (200 keV)-1 E, keV L=6,28м L=8,38м L=10,48м

Reactor power 90 MW

γ-background inside passive shielding depends neither reactor power nor distance to reactor

0MW reactor power 90MW reactor power

Fast neutron flux outside and inside passive shielding

20 40 60 80 100 120 20 40 60 80

Flux, (10-5 s-1 cm-2) Reactor power, MW

Fast neutron flux 10-3s-1cm-2, cosmic background level Fast neutron flux 9×10-5s-1cm-2

Neutron background inside passive shielding less by an order of magnitude than outside

• utside (near reactor wall)

inside

Background suppression

First AS version suppress background by an order of magnitude

Making full-scale detector

• Cell structure (50 cells)
• LAB-based Gd loaded

(1g/l) LS

• Hamamatsu R5912 (35)

and PMT 9354 (15) only from above

• Downside volume for

active shielding

Full-scale detector installation

• 1. detector (5x10 cells)
• 2. internal active shielding (AS)
• 3. external AS (umbrella)
• 4. steel and lead
• 5. borated polyethylene
• 6. moveable platform
• 7. feed screw
• 8. step motor
• 9. shielding against fast neutrons

from iron shot

Multi-section structure

Multi-cells prompt signal condition completely suppresses fast neutron correlated events

24 central and 16 side cells for full-scale detector central cell side cell angular cell in all cells 0.42 0.29 0.19 0.37

Average ratio multi/every for full-scale detector (0.37 ± 0.04)

Measurements with full-scale detector cell prototype

Measurements with detector

Reactor ON and OFF spectra after 1 month exposition at 7.11m 181 /10 (ON – OFF). S/B = 0.57 Unavoidable background of Li9 and He8 is 86 events/105s

Distance dependence with Neutrino-4 detector and DANSS

DANSS distance dependence provided by prof. M. V. Danilov

Well agreement with 1/L2 for now

Model independent analysis on DANSS and Neutrino-4 distance dependence

• Method of oscillation

parameters estimation by flux distance dependence measurement is sensitive in range (without comparison expected and

• bserved absolute values)
• If distance

dependence deviation from 1/L2 show itself evidently only at L < 5m and hard to be observed

e



2 2 14

1 m eV  

2 2 14

1 m eV  

Spectra at different distances with full-scale detector

Results of measurement with full-scale detector (spectral)

In ratio observed/expected we use average (over all distances) spectrum and MC modeling result to improve statistical accuracy

Results of measurement with full-scale detector (spectral)

• This analysis is model

dependent and these results are very preliminary. Areas of possible parameters are caused mostly by deviation in 3 – 4 MeV range.

• For model independent

analysis we need better statistical accuracy which we can’t be achieved only by continuation of data collecting

Future plans

• 1. External AS
• 2. Internal AS
• 3. CH2B
• 4. Transverse sections
• 5. Longitudinal sections
• 6. PMT
• 7. Gamma-catcher
• 8. Scintillator
• 9. Moveable platform
• Collaboration with

NEOS and DANSS

• Baseline 6-14m
• Two identical detectors
• Cell structure
• Expect better energy

resolution

• PSD capability due to

NEOS scintillator and double ended readout

Measurements with future detector cell prototype

Future plans

• Collaboration with

NEOS and DANSS

• Baseline 6-14m
• Two identical detectors
• Cell structure
• Expect better energy

resolution

• PSD capability due to

NEOS scintillator and double ended readout

Method Factor Relative error after 1 year of measurements with 2 detectors for each of 6 points Initial value

• 15%

Gadolinium concentration 0.5%

4x acc. bg. suppression

11% 3d sectioning

3x acc. bg. suppression

8% Pulse form

5x corr. bg. suppression

6% Efficiency

2x count rate

3%

Summary

• Neutrino-4 experiment for the first time measure reactor antineutrino

flux distance dependence in range 6-12m

• Full-scale detector measurements last results (spectra and flux distance

dependence) are presented

• There is a good agreement with 1/L2
• It is possible to measure reactor antineutrino flux and spectrum at

Earth surface in difficult background conditions, but improvements needed

Thank you.

Collaboration Neutrino-4:

• 1. NRC “KI” Petersburg Nuclear Physics Institute, Gatchina,
• 2. NRC “Kurchatov institute”, Moscow,
• 3. JSC “SSC RIAR”, Dimitrovgrad, Russia
• 4. DETI MEPhI, Dimitrovgrad, 433511 Russia

A Serebrov1, V Ivochkin1, R Samoilov1, A Fomin1, A Polyushkin1, V Zinoviev1, P Neustroev1,V Golovtsov1, A Chernyj1, O Zherebtsov1, V Martemyanov2, V Tarasenkov2, V Aleshin2, A Petelin3, A Izhutov3, A Тuzov3, S Sazontov3, D Ryazanov4, M Gromov3, V Afanasiev3, M Zaytsev1, 4, M Chaikovskii1