First Observation ofCoherent Elastic Neutrino-Nucleus Scattering(CEνNS)

Jonghee Yoo

2018-01-11
University of Tsukuba

Science Cover 2017-09-15

Yoo-2018-01-11 @ Tsukuba2Coherent Elastic Neutrino-Nucleus Scattering (CEvNS)
Straightforward calculation given the existence of weak neutral current
CEvNS has not been observed since its first prediction in 1974

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CEvNSGF µl jµ
Lef f =
2
Cross section for zero-momentum transfer limit⇥ N '42E [Z⇤p + (Ag(Z0 u) =

⇥p =

14

2
sin2 W ,3GF
(4 sin2 W
4Z)⇤n ]

1 1+ sin2 W
4 3g(Z0 d) =1),⇥n =2GF
4Differential cross section for finite momentum transferG2Fd⇤=[(1dE4⇥Yoo-2018-01-11 @ Tsukuba

4 sin2w )Z(A2Z)] M

✓

1ME
2E 2

◆

F (Q2 )24

CEvNS Crossection

Largest cross sectionin the region of interest
For most of the detector target
nucleus, the coherence condition
is fulfilled by neutrino energy ofE <Emax

1' 50 MeVRN
2E 2MO(100) keV

Recoil energy is tiny

K.ScholbergRequires a ton-scale detector with ~10 keV energy threshold◆ ✓◆⇣⌘ ✓⇥MR ⇥ O(103 )events/year
10 39 cm21013 /year/cm2ton
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5Why CEvNS? — Weinberg Angle
θW is a free parameter in Standard Model.
There is no fundamental theory which explains its value.
2GF2 Eν2 ⎡222⎤
σ tot =Z
1−4sinθ−NF(Q)()
W⎣⎦4π

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Why CEvNS? — Non Standard Interactions
SILN⇤H =GF⇤2[¯⇥q=u,d,⇥=e,µ,⇤µ(15)⇥⇥ ] ⇥ (⇤qL⇥ [q̄ µ (15)q] + ⇤qR⇥ [q̄ µ (1 +5)q])

JHEP 03(2003) 011

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Why CEvNS? — Sterile Neutrino Search

PRD 86 013004 (2012)

The development of a coherent
neutrino scattering detection
capability provides the mostnatural way to explore thesterile neutrino sector.
The neutral current interactionis the obvious way to probe
non-active neutrino flavor stats,as the interaction sensitive toall active neutrinos.

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8Why CEvNS? — Neutrino Magnetic Moment! Magnetic moment of neutrino enhances the recoil energy spectrum at low energy➔ requires very low energy threshold detectord⇡↵2 µ2⌫ Z 2=dEm2e

✓

1E/k
E+ 2E
4k

present limit◆Ne targetµBµB

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9Why CEvNS? — Supernova
Large effect on Supernovae dynamics.
The measurement of CEvNS will validate the supernova explosion models

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10Low Background & Low Energy Threshold Detector
Recent innovation of Dark Matter detector technology
makes it possible to access CENNS(<100 keV energy thresholds for nuclear recoil w/ low BG)

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11Neutrino Background

Dark Matter Search
Recoil Energy range

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12Neutrino Background

CoGeNT(2012)
CDMS Si(2013)
DAMA

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CEvNS at Reactors

Reactor neutrino spectrum
H. Murayama and A. Pierce
hep-ph/0012075

2E 2Emax '< keV
M= 1020 ¯e /sec/4⇥R2(= 1012 ¯e /sec/cm2 @ 20 m)● Requires Ultra-clean, kg-size, ~100 eV threshold detector● Need to overcome steady state backgrounds and detector noise● Reactor off-time can be used for background subtraction● Detector development is very challenging for a realistic experiment
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Oak Ridge National Laboratory (Spallation Neutron Source)

Proton LINAC
Accumulator Ring
TargetYoo-2018-01-11 @ Tsukuba

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Oak Ridge National Laboratory

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Neutrino Production at SNS● Spallation Neutron Source (SNS) at Oak Ridge National Lab
F. Avignone and Y. Efremenko, J. Phys. G, 29 (2003) 2615-2628• Flux ~ 107/sec/cm2 at 20m from the target• 60 Hz pulsed source• Steady-state background rejection factor ~10-4• Expected event rate in a single-phase 500kg LAr detector: ~890 events/year ofdetection (Eth>20 keV) at the proposed experiment site (46m from SNS target)

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Neutrino Production at SNSe+𝜋+µ+τµ = 2.2µs⌫µ

Prompt⌫e

Delayed⌫¯µDelayed⌫µpcapture

1GeVe-Hg

µ𝜋-

⌫µ99%

neutrons
Yoo-2018-01-11 @ Tsukuba⌫¯ecapture⌫¯µ18

Neutrino Energy Spectrum from SNS

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Neutrino Timing Profile at SNS

in time with beam

• 60Hz repetition rate pulsed source• ν Flux ~ 107/sec/cm2 at 20m from the target• Steady state background rejection factor ~10-4• 1 µs width POT spills (5× 1020 POT per day)delayed by muon decay (2.2µs)

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SNS Experiment Projects

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Neutrons in SNS (Simulations)!

Proton Transport BeamYoo-2018-01-11 @ Tsukuba

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Neutron Background Measurement at SNS

Neutron flux in the target building
104 times more than allowed level
for the CEvNS measurement.
During the survey COHERENT
collaboration found a very
interesting location.
➔ a very narrow hall way
in the basement area of thetarget building
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Neutron Background at SNS Target Building

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Neutrino Alley(29m from the target)(20m from the target)! The basement location (now called Neutrino Alley) is isolated from neutron beam lines! SNS target to the Neutrino Alley is filled with concrete and gravel (12m of void free region)! 8 m of water equivalent overburden (it’s in the basement — additional shielding)# Discovery of the location! (Flux = 1.7× 1011 νµ /cm2/s @ CsI)
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COHERENT Phase-1 Experiments
14kg CsI detector

10kg HPGe detector

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30kg LAr detector

185kg NaI detector

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CsI Crystal Detector# CsI detector characteristics- High density 4.51g/cc- Can be built for low radioactivity- Very high light yield ~18pe/keVeebut ~1.17pe/keVnr for nuclear recoil- Inexpensive ~1$/g

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CsI Detector Quenching Factor

The quenching factor used forthe publication: 8.8%±2.2% flatYoo-2018-01-11 @ Tsukuba

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CsI Detector Installation

3” HDPEaroundWater
BricksTop

Hand held
neutrino
detector

Muon
Panel

Base

Muon panels allover around
LB lead

Water
BricksSides

You can stacklead in N.L. !!!

FinalTouches
State of the Art HV system

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COHERENT Phase-1 Experiments

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CsI Detection Efficiency

Detection efficiency
calibration using Ba-133
source (@UChicago)

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CsI Detector Stability Monitoring

Beam power

Expected muon rate at SNS

Reduced big signals over time

Low rate of very large events

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COHERENT Phase-1 Experiments
Detector Calibration at SNS (during the data taking)Yoo-2018-01-11 @ Tsukuba

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Signal Efficiency Based on Ba Calibration

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CsI Detector Data Accumulation# Total 1.76×1023 Protons on Target were recorded (7.48GWh, 308 days)# 0.22 grams of protons are delivered to the SNS target
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CEvNS Observation! The first observation of CEvNS at a 6.7-sigma confidence level! Smallest neutrino detector ever (14.6kg)!

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Constrain on Non-Standard Neutrino Interactions
SILN⇤H =GF⇤2[¯⇥q=u,d,⇥=e,µ,⇤µ(15)⇥⇥ ] ⇥ (⇤qL⇥ [q̄ µ (15)q] + ⇤qR⇥ [q̄ µ (1 +5)q])

90% C.L.

SM!

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Citationad5tefaysYoo-2018-01-11 @ Tsukuba

ERHr COr
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Liquid Argon CEvNS Detector: CENNS

1-kg detector 2012
• Operationalexperience• Measure scintillation
light efficiency ofnuclear recoils in LAr

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10-kg detector 2013~2014• Study beam induced
neutron shielding near thebeam target• Characterize the BNB
neutron backgrounds inLAr target• Understand design issuesof the ton-scale detector(LAr detector test stand)Ton-scale detector
for the CENNS
experiment39

CENNS Detector R&Dpn1-kg LAr prototype detector! SCENE Collaboration: (CENNS+DarkSide)
SCintillation Efficiency of NobleElements! Goals:Measure scintillation light yieldin low-energy (<50 keV) nuclearrecoils! Can run in single-phase modeor dual phase TPC mode
! Use pulsed neutron beamat University of Notre Dame
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CENNS Detector R&D
Pulse Shape Discrimination

83Kr source

F90

Gamma Light Yield (single phase)

npeElectron Drift time (145us)! Detector performance is good enoughto carry out in-beam measurement! Date taking at the end of 2012 and early 2013

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CENNS Detector R&D
Van de Graaff (Notre Dame)

Neutron Beam Data (before cut)

LAr detector center

neutrons

Neutron Beam Data (after cut)Yoo-2018-01-11 @ Tsukuba

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CENNS-10@Fermilab

10-kg prototype detector! Goals:- Neutron background study at BNB area
- Demonstrate detector capability! Existing cryostat and gas handling systemfrom 1-kg prototype! Parts are ordered and/or purchased! Initial phase will use two R5912-02MOD
8” PMTs (Hamamatsu)# Construction completed in October 2013

Water

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CENNS-10@Fermilab

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CENNS-10@Fermilab

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CENNS-10@ORNL

Data taking started in August 2017
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CCD Camera for Dark Energy Survey

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CCD Detector for CEvNS

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CEvNS with CCD detector

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CEvNS with CCD detector

muons: long trackYoo-2018-01-11 @ Tsukuba

spot-like: potentially nuclear recoil interaction
electrons:
scattered track (surface)50

CEvNS with CCD detector

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New CCD Development
CCD detector now

Skipper CCD (new development)

New CCD technology demonstrated (arXiv:1706.00028) allows reduction of
the energy threshold by another factor of 2.
The goal of CCD based detector R&D is to lower the energy threshold down toorder of 10s of eV
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Remote Monitoring of Nuclear Reactions?

2E 2Emax '< keV
M= 1020 ¯e /sec/4⇥R2Yoo-2018-01-11 @ Tsukuba(= 1012 ¯e /sec/cm2 @ 20 m)

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A Test CCD at KAIST

from Juan Estrada (Fermilab)
for DAQ development andperformance test

1cm

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CubeSat

Image from NASA Cubesat
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Summary! COHERENT collaboration observed CEvNS process
for the first time at Oak Ridge National Laboratory! COHERENT collaboration will further establish
the CEvNS process using different target material detectors! There are vigorous R&D efforts to utilize the CEvNS process
for various applications

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