Takasumi Maruyama (KEK) for JSNS2collaboration

2019/9/17

International School of Nuclear Physics
41st course (Erice-Sicily)1Sterile neutrinos• Sterile neutrinos could give an insight for the questions
beyond the standard model; (E.g.; PLB 631, 151 (2005))– No strong, electro-magnetic, weak interactions.
– Introduced to explain both results of LSND (later we show) and LEP(:there are only 3 weak interactive neutrinos below 45GeV)
experiments– Observed by mainly neutrino oscillations (?)• Beyond PMNS matrix oscillation– Could be nR (Majorana) or new particle– LSND, MiniBooNE, reactors, Ga experiments indicate the existence.

• sterile neutrino could be a dark matter candidate ?

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Indication of the sterile neutrino (Dm2~1eV2) ?
• Anomalies, which cannot be explained by standard neutrino
oscillations for ~20 years are shown;

2019/9/17

Experiments

Neutrino source

signalsignificanceE(MeV),L(m)LSND

m Decay-At-Rest

nm → ne

3.8s

40,30

MiniBooNE

p Decay-In-Flight

nm → ne

4.5s

800,600

nm → ne2.8s

combined

4.7s

Ga (calibration)e capture

ne → nx

2.7s<3,10Reactors

Beta decay

ne → nx

3.0s

3,10-100• Excess or deficit does really exist?
• The new oscillation between active and inactive (sterile)
neutrinos?
• (Note: no indications in nm→nm , recent reactor experiments
using energy spectrum have negative results)

Please also see
M.Dentler et al
JHEP 08, 0103(2018)
for recent reviews

2019/9/17

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Appearance (LSND)

LSND

me Signal

c43

1998 at LANL

600ms 120Hz
target+beam stop
configuration
DIF, n bkg.
p → m + nmm→ e + ne + nm² + # m +! m nee +! e! mOscillations?

!ep-, LSND
m- absorbed
beforedecay
into n’s andin conjunction
withthe atmospheric-4
thereshould
not bene needs
at themore
levelthanof 7x10
solaroscillation
results
3 n’s

Saw an excess of:
87.9 ± 22.4 ± 6.0 events.
With an oscillation probability of(0.264 ± 0.067 ± 0.045)%.
3.8 s evidence for oscillation.

Þ Models developed with 1 or 2 sterile n’s

2019/9/17

Signal : ne p→e+n np→d g(2.2MeV)

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MiniBooNE results (2018)
8GeV

fromFNAL Booster

Mineral oilCherenkov• Significant low energy events excess is observed. (4.5 s)• They claimed that this excess is due to the same
phenomena as LSND experiment.
• Concerns are– Systematic uncertainties (neutrino interactions, backgroundunderstandings)– Especially, unknown single gamma production events may
cause this.

• MicroBooNE (Large Liquid Ar TPC detector) is checking theneutrino interaction mode.
2019/9/17

Neutrino2018
En-Chuan Huang

Current situation / what experimentalists should doet al• 3+1 oscillation model cannot explain all M.Dentler
JHEP 08, 010 (2018)
phenomena from various experiments.
• If nm→ne anomalies are confirmed (highsignificance but maybe not the issue of level ofs) but the nm→nm (and ne→ne) bounds are notrefuted, we absolutely need new physics model.
• Or experimental data is something wrong?? This part is being andwill be examined by experimentalists extensively.

– MicroBooNE (running) / FNAL SBN (SBND+MicroBooNE+ICARUS) for MiniBooNE anomaly– JSNS2 for the LSND experiment
7– Many reactor experiments are on-going, thus they can check further.

J.Spitz’s talkin NuFact2019

Direct test for MiniBooNE
Anomaly.
8Collaboration meeting @ J-PARC(2019/July-Aug)

JSNS2 collaboration (55 collaborators)• 6 Japanese institutions (27 members)• 10 Korean institutions (20 members)• 1 UK institution (1 members)• 5 US institutions (7 members)

Direct tests for LSND.

JSNS2: J-PARC E56
Sterile n search@MLF

400MeV

J-PARC Facility(KEK/JAEA）
South to North

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

3 GeV RCS
Neutrino Beams(to Kamioka)

25Hz, 1MW (design)

Successful 10.5 hours
1MW trial performedon 2019-July-3

Materials and Life
Science Experimental
Facility (MLF)

Hadron hall
Bird’s eye photo in January of 2008

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JSNS2 setup at J-PARC MLF
MLF building (bird’s view)

Detector @ 3rd floor(24m from target)

Hg target = Neutron
and Neutrino source

50t liquid scintillator detector(17t Gd-loaded LS in target)(4.6mf x 3.5m h)~120 10” PMTs
image

3GeV pulsed
proton beam

Searching for neutrino oscillation : nm → ne with baseline of 24m.
no new beamline, no new buildings are needed → quick start-up

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Neutrinos Production and Detection• Large amount of parent m+ in Hg target → nm are produced.
• If sterile n exist, nm → ne oscillation is happened with 24m.
• Oscillated ne is detected by Inverse Beta Decay (IBD): ne + p → e+ + n w/ wellestablished detector technique(E resolution = 15%/sqrt(E))

3GeV
pulsedprotonbeam

2019/9/17(Decay-at-Rest)
Scintillation lightp+

IBD criteria

TimingEnergyPrompt1<Tp<10μs

20<E<60MeV

DelayedTp<Td<100μs

7<E<12MeV<T>~30msScintillation light(~ 8MeV In total)

Most of them
are same as
The LSND.
→ Direct ultimate
tests for LSND.
But use muchbetter beam andGd loaded LS.
→ Much better
S/N→ Much bettersystematics

Timing and Energy

M. Harada et al, arXiv:1310.1437
Next beam is 40ms laterp timing

Selecting muon decay(e~74%)

Timing and Energy are friends of JSNS2➢ Timing: Ultra-pure n from m+ Decay-at-Rest➢ n from p and K -> removed with timing➢ Beam Fast neutrons -> removed w/ time
➢ Cosmic ray BKG -> reduced by 9ms time window.

➢ Energy: signals / BKG separation by energy.

➢ n from m has well-known spectrum.
➢ Energy reconstruction is very easy at the IBD. (En~ Evis + 0.8MeV)➢ n from m- is high suppressed.

2019/9/17

IBD event selection
casen capture
2; Prompt signal E cut

3. Delayed gamma E cut

4. Distance cut between
prompt vertex anddelayed vertex
4. Dt cut between promptand delayed(~30ms lifetime for n )2019/9/17

Selection e~ 38%

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#events (1MW x 3 years x 1 detector (17tons))
Sourcecontents#ev.(17tons x 3years)

Reference : SR2014(50tons x 5 years)

commentsbackgroundne from m-

43237

Dominant BKG

12C(n ,e-)12N
eg.s.

316

Beam fast neutrons

Consistent with 0< 2 (90%CL UL)<13

Fast neutrons (cosmic)~037

Accidental

20

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Based on real data

87480

Dm2=2.5, sin22q=0.003

62342

Dm2=1.2, sin22q=0.003

signalBased on real data

Accidental BKG is calculated by;R acc = SRprompt x SRdelay x DVTX x N spill
MLF best Dm2(2.5eV2)– SRprompt, SRdelay are probability of accidental BKG for prompt and delayed.
– DVTX ; BKG rejection factor of 50.
15– Nspill(#spills / 5 years) = 1.9x109

Sensitivity / Upgrade• To have a good international competition capability, we start the experiment withone detector (17tons fiducial volume).
• Even with one detector, we have a good 90% C.L constraints for LSND results for 3years. Left plot
• Meanwhile, we are making effort to obtain the budget to build the 2nd detector.
JSNS2ExploringRegion(90%)

LSND best (sin22q,Dm2)(0.003, 1.2eV2)

3 years x MW x 17 tons
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Achievements so far• 2013 Sep; A proposal was submitted to the PAC• 2014 Apr-Jul; We measured the BKG rate on 3rdfloor. -> manageable beam /cosmic BKGs toperform JSNS2 (PTEP 2015 6, 063C01)• 2014-Dec; The result was reported to J-PARC
PAC. → the stage-1 status was obtained.
• 2016-June: The grant was approved for one
detector construction• 2017-May: Technical Design Report wassubmitted to J-PARC PAC and arXiv(arXiv:1705.08629 [physics.ins-det])• 2018-Nov: The stage-2 (“go-sign” of starting theexperiment) from KEK/J-PARC was granted.
• We aim to start JSNS2 in JFY2019, the detector
construction will be completed soon.

2014BU1301
experiment (@MLF 3rd floor)
Proton beam
Signal region forprompt signal
BKG ~ 0

Energy (MeV, vertical) vs timing (ns, horizontal)

Stainless tank construction• Construction at J-PARC (2017/Dec – 2018/Feb)• Water leak test was done on 2018/Feb.
• L-type angles, stainless plates were welded tothe tank to install PMTs and acrylic tank.
(bottom-right picture)• This tank was moved from the construction
place to assembly building.

2017/Dec/25

2018/Feb/28

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Acrylic vessel installation rehearsal (2019/Feb)• Feb-18: the acrylic vessel arrived from Taiwan.
• Immediately after the arrivals, we had rehearsal
to install the acrylic tank. → succeeded.
• Currently, the acrylic tank was out of detector toinstall PMTs.

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10” PMTs• 67 RENO experiment spare
PMTs were rental to JSNS2.
• 13 Double-Chooz spare PMTs
were also borrowed.
• 80 PMTs are now at J-PARC.
Most of them were precalibrated and installed to thedetector.
• ~50 more PMTs will come to JPARC from 2019 Sep to Dec.
• Soon after the installation ofthese ~50 PMTs, we will startdata taking.
2019/9/17

PMT pre-calibration• Gain, P/V ratios, Dark rate (@ 107 gain) measurements
for 8 PMTs at once
• 8 PMTs/day can be pre-calibrated.
• charge info. is much more important than timing for
JSNS2’s reconstruction because of several 10 MeV.
14bits CS-ADC
MultiHit-TDC

Pico-second
Laser Pulser

Gate,StartLaser
headOpt.
fiber

1-to-8 laser splitterHVADC, Sig.
Splitter
8 ch.
TDC

The system has been launched at J-PARC• Typical 1 p.e. dist. with various HVs.
• Currently most of arrived PMTs were pre-calibrated.
• A few PMTs have troubles. → rejected to use.

PMT Installation status• Immediately after the precalibration (and the results areOK), we can install the PMTs inparallel to the pre-calibration
works.
• We already installed 67 PMTs tobarrel and veto parts. (remainingPMTs will be installed soon)• After the installation works, one
by one checks of PMTs signal
were and will be done. → so far,installed PMTs have no problems
to see the signal.
2019/9/17

International School of Nuclear Physics 41st course (Erice-Sicily)22Liquid Scintillator (LS) Production in Korea (2018)

LS storage in Japan

35 tons of LS was produced at RENO site and delivered to Japan with two iso-tanks.

Date

Job description

Sep. 12 - 18

Refurbishment and cleaning

Sep. 28

ISO tank arrived at RENO site

Oct. 1 - 22

LS production (6 shift periods)

21 batches in total (37000 L)- 4 peoples per day- 2 of ISO tanks

First sampling test in Japan

Gd-loaded Liquid Scintillator is donated from Daya-Bay• Daya-Bay experiment kindly donated the 20
tons of Gd-loaded Liquid Scintillator (GdLS).
→ JSNS2 would express deep appreciatiation
for this.
• On 2019 August-1, the GdLS passed Japanesecustom.
• We visited the GdLS/LS storage area andobtained samples on Aug-6.
• We did measure the optical properties at
Tohoku Univ.. They look nice.
Values

MethodAbsorbanceSee right plot

UV-Vis spectrometer

Light yield

11.7 photon/keV

Back scattered g of 137Cs

Gd concentration0.096+-0.002 w%

EDTA Titration

GdLS
pureLS

Absorbance SpectraNeutrino-nucleus interaction in Type-II SN
n-A interactions are important in⚫ core-cooling by n-emission⚫ n-heating on shock wave
⚫ n-process of nucleosynthesis⚫ efficiency of neutrino detectors
Reaction rates are to be knownwith accuracy better than ~10%!

Experiment
KARMEN (PLB332, 251s(12C(ne,e-)12Ng.s.) (10-42 cm2)
9.1±0.5±0.8 (10.4%)(1994))

LSND (PRC64, 065501 (2001))
2019/9/17

JSNS2 (arXiv:1601.01046)

8.9±0.3±0.9 (10.7%)(~3%(stat.) expected in 5yrs)

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50-100 events / day with 1MW beam
2019/9/17

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Summary• If sterile neutrinos exist, it opens the era of new physics.
• There are a lot of experiments on going to search eV scale sterile
neutrinos. Recently, direct confirmation or refuting of LSND andMiniBooNE experiments are getting crucial.
• For the direct test for LSND experiment, the JSNS2 experiment will startdata taking very soon.
• Same neutrino sources (energy, flavor), neutrino target and interaction are used.
• But using much better quality of beam (on duty factor) and Gd-loaded liquid
scintillator. → can improve signal-to-noise ratio (~100 for accidental BKG)
• We will complete the detector construction soon.
• First physics run for 3 years, but meanwhile requesting budget for the 2nddetector.

• Other physics topics are also interesting! You can see the results soon !!
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backup2019/9/17

International School of Nuclear Physics 41st course (EriceSicily)28

Detector moving to assembly building（2018/Mar)
Crane work

Tank was put on the low bed Trailer

Around accelerator controlbuilding

Shutter ofassemblybuilding

assembly building“M1” (construction)
To “HENDEL”(assembly)

Around assembly buildingThis work was successful w/o problems!

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