Coherent neutrino scattering
status and perspectives
Yu. Efremenko
UTK/ORNL
Lomonosov-2021, August 251

Coherent Elastic Neutrino Nucleus Scattering (CEvNS)
A neutrino scatters on a nucleus via exchange of a Z,
and the nucleus recoils as a whole

2

CEvNS cross section is predicted by the Standard Model !!!

Coherent Elastic neutrino-Nucleus Scattering (CEvNS)
CEvNS cross-section is larger than any
other neutrino interaction cross-sections
at low energy, but it is hard to detectCsI CEvNS133
Cs CEvNS127
I CEvNSν e 127I CCIBDν e-e

Cross-section (10-38 cm2)

101Pb ν e NIN total
Pb ν e NIN 1nPb ν e NIN 2n10−1

10−210−353101520253035Neutrino Energy (MeV)

40455055

Nuclear Form Factor at CEvNSFor energy above 50 MeV
form factor starts to suppress cross section
DARCEvNS

CEvNS after correction
by nuclear form factor

4CEvNS belong to both Particle and Nuclear Physic

High Q = shortde Broglie
wavelength

Low Q = longde Broglie
wavelength

CEvNS will let to Measure Neutron Skin for Heavy
Elements à input into neutron matter density

Fattoyev, F.J. etal. Phys.Rev.Lett. 120 (2018)

5C.Horowitz

CEvNS is Neutrino Floor for DM Experiments

6CEvNS is a Probe of Non-Standard Neutrino Interactions (NSI)SILN⇤H =GF⇤2

new interaction specific to n’s[¯⇥µ(1q=u,d,⇥=e,µ,⇤J. High
EnergyPhys.Phys.
03(2003)
011 011
J. High
Energy03(2003)

5)⇥⇥ ] ⇥ (⇤qL⇥ [q̄ µ (15)q] + ⇤qR⇥ [q̄ µ (1 +5Non-Standard 𝛎 Interactions(Supersummetry, neutrino mass models)can impact the cross-section differently for
different nuclei

Charm experiment7)q])

CEvNS are Important as a Probe for NSI.
NSI can create degeneracy for DUNE~$1 billion project– measuring the charge-parity (CP) violating phase CP,– determining the neutrino mass ordering (the sign of Δm212)– precision tests of the three-flavor neutrino oscillation
paradigm
arXiv:1604.05772v1

NO w/noNSI...

8

If you allow for NSI to have non-zerocontribution, degeneracy appears.

...looks justlike IO
w/NSI

We can not tell the neutrino mass ordering inDUNE without constrains on NSI

CeVNS is a new way to measure Electro-Week angle at Low Q
2GF2 Eν2 ⎡222⎤
σ tot =Z
1−4sinθ−NF(Q)()W⎣⎦
4π

Measurements with targets having
different Z/N ratio are required.
Sun2θw is a free parameter in the Standard Model
There is no fundamental theory which explain its value
It is “running” constant and its value depends on the momentum transfer.
Proposed correction to g-2
for muon magnetic moment
due to a light mediator

9If this is correct it can manifest
itself in θw value at low Q2

Search For Neutrino Magnetic Moment via CEvNS
Signature is distortion at low recoil✓ energy Ed⇡↵2 µ2⌫ Z 2=dE
m2e

1E/k
E+ 2E4k◆

Ne targetµBµB
Present Limitèrequires detector with very low energy threshold
10See also Kosmas et al., arXiv:1505.03202

CEvNS important for Understanding of Supernova Dynamics
Large effect from CEvNS on Supernovae dynamics.
We should measure it to validate the models J.R. Wilson, PRL 32 (74) 849

1111

Worldwide Efforts to Measure CEvNS

CaptainMills

Except COHERENT and Captain Mills collaboration, all others are attempting to use
nuclear reactors as a neutrino source
12

Nuclear reactors gave a large constant low energy neutrino flux

COHERENT Is Using Spallation Neutron Source (SNS) à (SvS)• It is world most powerful pulsed neutrino
source. Presently it delivers 7・1020 POT daily~10% of protons produce 3 neutrino flavors• Neutrino energies at SNS are ideal to study
CEvNS.
For 99% of neutrinos En < 53 MeV• Decay At Rest from pions and muons (DAR)
gives very well-defined neutrino spectra• Duty factor suppress steady state backgrounds
by a factor of 2000.
It is like being at the 1000 m.w.e underground

LINAC:

××× x ~1000 ×××

Accumulator Ring:
13600 nsec
Repeat 60/sec.

Neutrino Production at the SNS~99%

p-SNS
14t » 26 nsecµ+p+t » 2200 nsec

Fragments

nµ

3000

Neutrino Timing

2000
0246!s8e+nµ1000

Neutrino Energy

ne0p~

Hg

neutrinos cm-2 s-1 ns-1 @ 20m

21cmeVG1CAPTURE

10

COHERENT is using “Neutrino Alley” at the SNSAfter extensive background studies we find awell protected location at the SNS basement

Physicists who are trying to put neutrino
detector next to a powerful neutron
source should always remember:
The Legend of Icarus

don’t try to fly too close to the sun
Neutrino Alley is 20-30 meters from the target. Space between thetarget and the alley is completely filled with steel, gravel andconcrete. This gives good protection from SNS neutrons.

Utility tunn
15el àNeutrino Alley

There are 10 M.W.E. of shielding from above, enough to kill hadronic
component of cosmic rays and attenuate muon flux by a factor of 3

COHERENT at the SNS
Location in basement of SNS target building(“Neutrino Alley”)
19-28 meters from the target

Nuclear
TargetTechnology

Mass (kg)Distancefrom source(m)RecoilThreshold(keVnr)CsI[Na]Scintillating
crystal

14.6

19.3

6.5

Ge

HPGe PPC

16

20

2-2.5

LAr

Single-phase

24

27.5

20

NaI[Tl]Scintillating
crystal

185*/3338

28

13

Enough place for a several detectors

Detectors

16

View looking down
Neutrino Alley12

First Experiment: 14 kg CsI Detector
Years of preparations, simulations, andshielding optimizations.
One day to install and to commission !!!
Muon
PanelBaseSingle 14 kg CsI crystal.
Crystal has been custom grown frompreselected low background materials
Layers of dedicated shielding:3” HDPEaroundLB leadPoly to protect from NINs
Lead Stacking

Low background lead
Regular good quality leadMuon
panels17

Veto system
Water
BricksOn Top

Water
BricksOn SidesFinalTouches

Water shieldingFirst Detection of CEvNS with CsI detector
CevNS cross section

16 month of dataCEvNS after correction
by nuclear form factor

1.4*1023 (~ 0.22g) P.O.T.

CEvNSFirst working, handheld
neutrino detector -14kg!!!

Presently we have x2.5 times
more statistics, and better
understanding of quenching
Will publish updated result verysoon
18

First detection.
27% accuracy
6.7 sigma

Argon Target•

Originally built in 2012-2014 by J. Yoo et al. atFermilab for CEvNS effort at Fermilab•

Moved to the SNS for use in COHERENT late
2016 after upgrades at IU. Rebuild in 2017 atORNL with new PMTs and TPB coating
sputtered in vacuum. L.Y. increased by afactor of 10.

•

10 cm Pb/ 1.25 cm Cu/ 20 cm H2O shielding•

24 kg fiducial volume•

2x 8” Hamamatsu PMTs, 18% QE at 400 nm•

Tetraphenyl butadiene (TPB) coated sidereflectors/PMTs•

Production Run starting July 2017.
19

Beam delivered to COHERENT detectors

CENNS-10 FirstProduction Run

CENNS-10 Calibration•

Calibrate detector with variety of gamma sources•

Measured light yield: 4.6 ± 0.4
photoelectrons/keVee•

83mKr injection system

At 83mKr energy (41.5 keVee), mean
reconstructed energy measured to 2%• 9.5% energy resolution at 41.5 keVee

Calibrate detector nuclear recoil response using
AmBe source
PSD vs reconstructed energy
10.9n recoil

F90

0.60.5e/g recoil

0.4

1Counts

0.7

10Counts

0.8Resolution 3 keVat 43 keV

0.3

600

Measured Photoelectrons

•57Co

241Am

40083mKrAmBe source data

200020

4060

80

100

10120140160

Reconstructed Energy (Photoelectrons)

180

200

nimil
re

300

200

P

100

0.2
0.1

yr
a500

−1

Reconstructed Energy (keVee)0020406080100

Reconstructed Energy (keVee)

120Fit Late Beam Related Neutrons
23 ± 8Predicted
SMCEvNS128
2 (-lnL)13.7± 17
Predicted
Beam Related Neutrons497
p-value
29%± 160
Predicted
Beam
Unrelated Background3154+±syst.)
25
Null
Rejection
Significance3.4 (stat.
Predicted Late Beam Related Neutrons
33 ± 33
Table 14:
Table 6:
Data Events
3752
Fit CEvNS
159 ± 43 (stat.) ± 14 (syst.)
Predicted
CEvNS
Fit Beam Related Neutrons
553 ±12834
Predicted
Beam
RelatedNeutrons
497
Fit Beam Unrelated Background3131 ± 23
Predicted
Beam
Unrelated
Background
Fit Late Beam Related Neutrons
10 ±3154
11Predicted
Late
BeamRelatedNeutrons
332 (-lnL)
15.0
Null Rejection Significance3.5 (stat. + syst.)
Table 7:

Likelihood Fit Results

21

Best fit CEvNS counts of 159 ± 43 (stat.) ±14 (syst.)• Result (stat. only) rejects null
hypothesis at 3.9𝜎
• Result (stat. + syst.) rejects null
hypothesis at 3.5𝜎
• Best fit result within 1𝜎 of SM prediction• Wilks’ Theorem checked with fake data
Presently we accumulated 3 times more statistics.
New results are coming soon

Table 15:310 SetDataNo-water
Water (5 days)
No-water
Water(5 days)
102cm2)•-40

3D binned likelihood analysis in energy,
F90, time space• Include both prompt and delayed time
regions

Cross section (10•Prompt Data
580 ± 25
23 ± 7580 ± 25
23 ± 7

Poly tank ⇢
1.9
3 1.9
0.95
0.95

MC Prediction
298
9.3
387
9.4 I Cs

Scale Facto
1.9
1.9
1.5
1.5

Table
Ge 16:

Data Set
Ar
No-water10
No-water
Full shieldNa
MC (in unblinded data)
101020

Energy Range
0-200 keVee
40-120 keVee
40-120 keVee
all ranges
30

Table 17:

Prompt Fit Mean (ns)
COHERENT
808measurements
754
SM prediction
630
FF = unity
710
Klein-Nystrand FF

4050
Neutron number

560

70

80

Prompt90

What Did We Learn After the First Results from COHERENT?
CEvNS does exists
However, nobody doubt that !!!

SNS is beautiful low energy
pulsed neutrino source“optimized” to study CEvNS

Now know how to detect
CEvNS“It’s a real thrill that something that I
predicted 43 years ago has beenrealized experimentally”
Daniel Freedman

So far, we have only three binary answers “Yes, Yes, and Yes”
Next step is precision study of CEvNS to search for unknowns !!!

For two first our results major systematical uncertainty is the knowledge of Neutrino Flux at the SNS ~10%22

100 cm Diameter

Concept of Heavy Water Detector

Prompt NC νμ +d à 1.8*10-41 cm2
Delayed NC νeμ-bar+ d à6.0*10-41 cm2
Delayed CC νe + d à 5.5*10-41 cm2Specifications• 0.8 tons D2O within acrylic
inner vessel• Water Cherenkov
Calorimetry

For 1 t fiducial mass detector ~ thousand
interactions per year• H2O “tail catcher” for highenergy e-Detector calibration withMichel Electrons from cosmic muons(same energy range)• Outer light water vessel
contains PMTs, PMT
support structure, andoptical reflector.

• Neutrino Alley space constraints for the
D2O detector:– 1 m depth x 2.3 m height x 3 m width• Outer steel vessel to• Lead Shielding• Hermetic veto system

220 cmS.Nakamura et. al. Nucl.Phys. A721(2003) 549

d2O

TeflonReflector• Locations 20-29 meters from target

23

Will do CC measurement on Oxygen for
SN support

H2O

Predictions for d2O detector response
See JINST 16 (2021) 08, P08048

24

SNS FutureToday••

2024 after PPU

900 users
Materials at atomic resolution
and fast dynamics

1000+ users
Enhanced capabilities

2.0 MW
1.3 GeV
27 mA
60 Hz

1.4 MW
1 GeV
25 mA
60 Hz

FTS
1.4 MW
60 Hz

25

•
•

2028 after STS••

2000+ users
Hierarchical materials, timeresolution and small samples

2.8 MW
1.3 GeV
38 mA
60 Hz

FTS
2 MW
60 Hz

FTS
2 MW
45 pulses/sec

The choice of 15 Hz and 0.7 MW resulted from a detailed analysis of STS design(reviewed by a panel of experts in 2017) and optimizes performance of STS
without impacting performance of FTS

STS0.7 MW
15 HzLong Term Program with Various Targets.
103

Cross section (10-40cm 2)

CEvNSfrom CM

102

yr
anim

Ge

10CEvNS after correction
by nuclear form factor

PNa

10il
reAr

I Cs

102030

40

50

60

70

8090

Neutron Number

To untangle effects of nuclear form factors weneed measurements at a wide range of target
masses: Light, Middle, and Heavy
To have handle on axial current it is interesting tohave close targets with different spins.
Example 40Ar s=0 and 23Na s=3/2

26

Future Activities - 1 ton LAr detector
Need high statistics low background measurements of CEvNS

Transition from 22 kg to 1 ton LAr detector.
Can fit at the same place where presently is CENSS-10
Will see 3kt of CEvNS events per year + CC

27

Interesting opportunity à Search foraccelerator produced
dark matter with LAr detector
arXiv:1911.06422 [hep-ex]

1 t Argon Detector

28

Same One Ton LAr Detector Can Measure Neutrino CC on Argon
This is the channel to detect Supernovae
Neutrino signal at DUNEThis is reaction which is never been measured !!!
29

Large NaI Detectors Array
Deployment later this year
Transition from now deployed 185 kg to 2 ton arrayof NaI detectors
Detectors are available
Need dual gain bases to look for
CEvNs and CC
Program to measure Quenching Factors at TUNL

Potential to detect both CEvNS and CC reactions
on Iodine30Germanium PPC array
Deployment later this year31

Summary
Detection of CEvNS on CsI and Ar targets opened new portal to look for physics beyond the SM
Neutrino Alley at the SNS is unique laboratory to study properties of CEvNSCOHERENT Collaboration is planning to build and deploy in a near future new sets of experiments:: 1t LAr(Xe), 1t D2O, 3t NaI, and 16 kg Ge, Xe target?

Why Measure Coherent !-Nucleus Scatterin

Particle Physics
NINs,Test of the SM, DM

Nuclear• Physics
Largest " in Supernovae dynamics. Astrophysics
We should measure it to validate theForm Factors, Axial Currents,
J.R. Wilson, PRL 32 (74Supernovae Cross Sections
Incoherent processes

See motivational opening talkby Karlheinz LangankeCO32

Supernova 1987aHE Charm
198
RE4NT
20
17

J.R. Wilson, PRL 32, 849 (1974)
C. Horowitz et al., PRD 68, 02005 (2003)

BarbeauCOHERENT CollaborationFebruary 2017 @SNS

21 Institutions (USA, Russia, Canada, Korea)
33