A few tens MeV ofneutrino physics
2in JSNS experimentWorkshop on Neutrino Interaction Measurements for Supernova Neutrino Detection
Oak Ridge National Laboratory
Mar 6th-8th 2023

Dongha Lee, KEK, on behalf of JSNS2 / JSNS2-II collaboration
122
JSNS / JSNS -II Experiments

Direct test of LSND.

Collaboration meeting @ J-PARC (2020/Feb)

JSNS2 collaboration (61 collaborators)- 6 Japanese institutions (29 members)- 10 Korean institutions (24 members)- 1 UK institution (1 member)- 4 US institutions (7 members)

JAEA
KEKKitasato
Kyoto
OsakaTohokuChonnam National
Jeonbuk National
Dongshin
GIST
Kyungbook
Kyung Hee
Seoyeong
SoongsilSungkyunkwan
Seoul National ofsci and tech

BNL
FloridaMichigan
Utah

SussexSpokesperson: T.Maruyama (KEK)
Co-spokesperson: S.B.Kim

2

2
Original motivation of JSNS
•Anomalies, which cannot be explained by standard neutrino
oscillations for a few tens years are shown;
Experiments

Neutrino source

signalsignificance E(MeV),L(m)LSNDµ Decay-At-Restνµ ! νe

3.8σ

40,30

MiniBooNE

π Decay-In-Flight

νµ !

νe

4.5σ

800,600

νµ ! νe2.8σcombined

4.7σ

We aim tohave a direct
test for thisGa (calibration)e capture

νe !

νx

2.7σ

<3,10Reactors

Beta decay

νe !

νx

3.0σ

3,10-100••

Excess or deficit do really exist?
Note: JSNS2 uses the same neutrino source (µ), target (H)and detection principle (IBD) as the LSND! even if this is not due to the oscillation, we cancatch this directly

3

JSNS2: J-PARC E56
2
JSNS -II: E82
400MeVSterile ν search@MLF
I'J9K''%&CC<>-;'-<'D<5-;!"#$%&'()*+,+-.
/0102!$1$3
Low duty factor beam(short pulse + small
repetition rate)
gives excellent S/N ratio.

http://research.kek.jp/group/mlfnu/eng

D9>-5+=<'49)E8F/-<'0)E+<G)H

25Hz, 1MW (design)

IAJ
9K'
L%

2021 physics run
0.6MW (Jan/12 – Apr/5 2021)
0.7MW (Apr/5 – June/22)L)-95+),8')=6'N+?9'
C*+9=*9'1O:95+E9=-),'()*+,+-.'/LN(H2022 physics run
0.7MW (Jan/28 – Apr/6 2022)
0.8MW (Apr/6 – June/3)M)65<=';),,

4+5678'9.9':;<-<'+='!)=>)5.'<?'@AAB

4

JSNS2 / JSNS2-II : Sterile Neutrino Search
MLF building (bird’s view)

Near detector@ 3F(24m from Hg target)

Hg target = neutronand neutrino source

Nucl. Inst. Meth. A
1014 (2021) 165742(JSNS2-I,ㅤJSNS2-II near detector
17t GdLS fiducial (target)(4.6m diameter x
4.0m height, 120 10” PMTs)

Far detector @Outside of MLF(48m from Hg target)

3GeV shortpulsed beam

Searching for neutrino oscillation : νµ ! νe withbaseline of 24m (near), and 48m (far detector)(JSNS2-II:Far detector)
32t GdLS(6.2m dia x
6.2m (h)~228 10”
PMTs)

Current JSNS2

Globalfit indicated region
M. Dentler,etal., JHEP08010 (2018)

JSNS2-IICovers theglobal fit indicatedregion nicely.

JSNS2-I : 1MW x 3years(near only)- commissioning (2020) :Eur. Phys. J. C (2022) 82:331- 1st/2nd long physics run (2021,2022)-> Smooth data taking (~0.5 year x 2)
- 3rd long physics run
will be started since 2023 Apr
JSNS2-II : 1MW x 5years(near + far)
- Proposal (2020) : arXiv:2012.10807- New far detector :32tons, 48m baseline- Good sensitivity on low Δm2 region- Two detectors withtwo di erent baselines ->a solid conclusion onLSND anomaly- J-PARC/KEK granted
the stage-2 status- PMT installation is on-going5

Sterile neutrino - production/detection
TimingSterile neutrino oscillation during 24m baseline.
PromptDetection by coincidence of IBD (Inverse Beta Decay)
Delayed-> Prompt : e+ annihilation-> Delayed : gammas from neutron capture on gadolinium (Gd)Liquidscintillator
is lled in thedetector

1.5 ~10μs frombeam
ΔTp-d <100μs

Energy20~60 MeV
7~12 MeV

Liquidscintillator
absorbsthesegammas,and emits
manyphotons.

fi6

2Operation in JSNS experiment==Commissioning run (2020 Jun 5-15) (0.6MW)==1st long physics run (2021 Jan 12 - Jun 22)-> 0.6~0.7MW-> ~13% of approved POT(3y) for JSNS2-I==2nd long physics run (2022 Jan 28 - Jun 3)-> 0.7~0.8MW-> ~10% of approved POT(3y) for JSNS2-I
There is an accelerator maintenance period every year.

- 24hours shift (on-site @ MLF
control room / remote shift)- smooth shifts withalmost no beam issue

Delivered POT : 2.77x1022(23% of approved POT(3y)for JSNS2-I)

7

MLF target & 3GeV proton beam...애널인데요

- Mercury target (annually exchanged vessel)- Highest pulse intensity in the world- Currently ~830kW beam.
-> ~900kW beam will start since 2023 Apr.
- Measurement of production rates(p + Hg -> π,Κ) is crucial.

8RoadMap for better sensitivity
Neutrino ux- Due to no π production measurementswith 3GeV p + Hg so far,+−-> Flux of ν¯μ from μ , ν̄e from μ have
~20 , ~50% error respectively(due to a few di erent results from MC models)
How to Improve (1) : ν¯μ from μ+- 12C(νe,e-)12Ngs measurements-> ν¯μ ux uncertainty could be reduced to~10% by ourselves- ν¯μ → ν̄e oscillation will be searched- This is currently assumed in TDR

How to Improve (2) : ν̄e from μ- No measurements like 12C(νe,e-)12Ngs- NA61 experiment (low energy beam-line)−-> measurements of π production-> aims to ~10% systematic error

ff

flBetter Sensitivity
fl−9

2Neutrinos in JSNS experiment
Sterile neutrino search (IBD)νeνe,e-)12Ngs

12C(ν̄e from μ−+−3GeV proton beam hits mercury target ; makes π DAR , π DAR+ +-> (1) π , μ channel ;-> ν¯μ → ν̄e : sterile neutrino search … detect by IBD signal-> 12C(νe,e-)12Ngs: even we cannot measure the IBD signal,measurement of CNgs can determine the number of ν¯μ(~10% uncertainty)
12C(νe,e-)12Ngs cross-section

from other experiments++μ → ν¯μ + νe + e ;assume the same numbersfor ν¯μ and νe(NA61 can also measureπ production directly)10νe

12C(122,e-) Ngs measurement in JSNSJSNS2 event selection in TDR

Prompt : Q-value is 17.3MeV

T1/2 = 15.83ms

Delayed :β-spectrum from Ngs

PromptDelayedarXiv:1601.01046v1-> Expected CNgs events in JSNS2 in TDR :~100 events / year / 1MW

ffi

ffi

ffi

R. MASCHUW (for the KARMEN collaboration),
Progress in Particle and Nuclear Physics 40 (1998) 183-192-> Analysis of the physics data is on-going-> Except Delayed timing,E ciencies look achievable ~ TDR level-> Delayed timing is driven by trigger ;2021 physics run data has ~12ms ; 50% e ciency
2022 physics run data has ~25ms ; 80% e ciency
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2Neutrinos in JSNS experiment
Sterile neutrino search (IBD)νeνe,e-)12Ngs12C(ν̄e from μ+−
Uncertainty ofν̄e from μ −−

3GeV proton beam hits mercury target ; makes π DAR , π DAR− −-> (2) π , μ channel ;− + − +-> Double Suppression of π /π , μ /μ ; ~10^-3 level.
−-> Due to Insu cient information of the p + Hg -> π ,large uncertainty (~50%) makes the sensitivity worse.
-> (it directly a ects to p-value-like estimation)

fl

ff

ffi

fi

-> NA61 experiment ; measure the rates of p + Hg -> π, K-> aims to reduce neutrino ux uncertainty to ~10%.
-> signi cantly better sensitivity (right plot)

Uncertainty of ν¯μ from μ + : 10%12

NA61 experiment
NA61 / SHINE @CERN SPS have a plan to built
1 ~ 10GeV/c π/K/p beam-line-> using NA61 detector + thin Hg target,measure p + Hg -> π, K cross section-> as mentioned, We aim to reduce the+ −uncertainty of p + Hg -> π , π rates to ~10%-> Also helpful for KDAR neutrinos cross-section measurement.

Angle [cosθ]

Hg target

Momentum [MeV/c]

13NA61 experiment
Our NA61 representative (Hasegawa) has
contacted to relevant CERN people closely.

Aerosol Cherenkov counter-> To separate Proton/Kaonfor 3.5 GeV/c beam (βP = 0.965, βK = 0.990)-> refractive index n = 1.03-> Cherenkov light
was confirmed

Normal Target
in front of VTPC

VTPC, GTPCMTPCs14

NA61 experiment2024 : one-week pilot run
2025 : several weeks physics data-> How to propagate NA61 results to JSNS2 is being discussed

15

- JSNS2 observed the clear signals of theKaon Decay-At-Rest (KDAR) Neutrino(Background: 5.2 +5.3 -5.2%)= 236= −- KDAR neutrinos is very good way forunderstanding the low energy neutrino interaction.
-> due to the well-known energy(Mono-Energetic neutrino at 236MeV)(106)

KDAR signal-> doublecoincidence- With NA61, an absolute KDAR neutrino
cross-section with a good precision
can be measured.

𝜇𝜈

𝑠𝑖

𝑉𝑒

𝑀𝑉𝑒

𝑀𝑚

𝜈

𝑣

Correlated/
BKG ID
Accidental
Correlated
1
Accidental
2
KDAR Candidates
730 events
𝐸𝐸𝐸

Observation of the clear KDAR signals

BKG(# of events)
36.6 +34.8 -34.6 5.0 +5.1 -5.0%
0.2 +- 0.01%1.5 +- 0.1
38.1 +38.4 -38.1

5.2 +5.3 -5.2%
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Toward Supernova physics

17

Core collapse of Supernova

18ν-heating ; energy transfer by ν-A interaction“3~12% increasein neutrino luminosity”
leads “matter” tohave sufficient energy ofSupernova explosion-> it largely depends
on the ν-A cross-section-> ν-A cross-section
should be knownwith ~10% accuracy.
19

SNν and DARνNeutrinos from mu-DAR
have a few tens of MeV ;-> similar level with SNν
-> Measurements of those DARν
can also be helpful for study of SNν

Solid line : SNνdotted line : DARν

20Measurement of ν-A cross section
Reaction

Neutrino Source

Accuracy

12C(νe,e-)12Ngs

Accelerator ν~10%

12C(νe,e-)12N*

Accelerator ν~15%

12C(ν,ν’)12C(1+1)

Accelerator ν~20%

12C(νe,e-)13N

Accelerator ν

76%

56Fe(νe,e-)56Co

Accelerator ν

37%

71Ga(νe,e-)71Ge

RI (51Cr)

11%

127I(νe,e-)127Xe

Accelerator ν33%<- JSNS2 can contribute<- JSNS2 can contribute

For the SN physics, precise measurements of “various ν-A interactions” are crucial.
-> There have been many measurements for various ν-A cross-section-> still error is large-> Also in JSNS2, those ν-Α cross-section could be measured.
-> C is in GdLS+DIN-> Fe in JSNS2 detector ; under private consideration (next page)-> Also, Any materials can be immersed in LS if needed.

21

56
56
2Example : Fe(νe,e-) Co in JSNS
Just p56Fe(νe,e-)56Co Interaction also can be measured

by inputting
stainless steel block at the center of the detector

rivateconsideration

now

Stainless steel block

For ~30kg of stainless block,~a few tens events of56Fe(νe,e-)56Co events / year
are expected (100% sig e assumed)with similar level of accidental background.
(~30% level uncertainty could be achieved)-> JSNS2 can easily take pilot run for this.
-> understand the energy/timing/background …
-> can lead to the next step (large statistics)

ff

2
JSNS can be ν-A measurement factory !!!

22

New Far detector

New Far detector-> PMT installation ison-going.
-> Beam-Neutron is~1/4 times of Near detector.
=> Better ν-Ameasurement capability.
Me23

Summary- Neutrino physics in JSNS2 experiment ;-> measurement of ν flux is crucial for better sensitivityof sterile neutrino search.
(CNgs, p + Hg -> π, K ; NA61 experiment…)- DARν have a similar energy range (a few tens of MeV) with SNν
-> Measurements of those DARν can also be crucial for study of SNν

- Precise measurements of “various ν-A interactions” are crucial for SN physics.
-> JSNS2 can be ν-A measurement factory !!!
24Backup25

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3GeV proton beam-> 3.8 x 10^22 POT /year(=5000h)27

Analysis in JSNS2 experiment- Beam trigger with 25μs width ; 2020 June ;Eur. Phys. J. C (2022) 82:331- From 2021/2022 physics run,-> Energy/vertex calibration-> Pulse shape discrimination (PSD) for neutron-like / electron-like-> Prompt/Delayed candidates for sterile neutrino IBD

28

29

Trigger implementation (coincidence trigger)
spill

on-bunch trigger

17 msbeam existing
signal

11 ussterile prompt trigger

Sterile prompt trigger efficiency
98.2 +- 0.4% @ 20MeV

threshold : 250 mV

12 mssterile delayed trigger (*)
threshold : 100 mV

Sterile delayed trigger efficiency
99.4 +- 0.1% @ 7MeV

- We made the coincidence trigger :Sterile delayed trigger only if there is a sterile prompt trigger -> Sterile neutrino search30