Takasumi Maruyama (KEK)2018/June/21

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 and LEP experiments– Observed by mainly neutrino oscillations– Could be nR (Majorana) or new particle– Beyond PMNS matrix oscillation– LSND, MiniBooNE, reactors, Ga experiments indicate the existence.

• Sterile neutrino could be also one of the Dark Matter candidate?

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

4.8s

Ga (calibration)e capturene → 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?

Neutrino oscillations with Dm2~1eV2 regioné n ù é U
ê e ú ê e1
ê n ú ê Uê m ú ê m1
ê n ú=ê U
ê t ú ê t1
ê ns ú ê Us1
ú êê
êë · úû êë ·Ue2 Ue3 Ue4 · ùúé n ù
ê 1 ú Matrix elements,
Um2 Um3 Um4 · úê n ú which are consideredúê 2 ú in 3x3 mixing
Ut2 Ut3 Ut4 · úê n3 ú framework.
úêú
Us2 Us3 Us4 · úê n4 úúê
ú· · úê · ú··ûûë(3+1) modelAppearanceLSNDme Signalc43

1998 at LANL

600ms 120Hz
target+beam stop
configuration
DIF, n bkg.
p → m + nm
m→ e + ne + nm

² + # m +! m nee +! e! mOscillations?

!ep-, LSND
m- absorbed
beforedecay
into n’s andin conjunction
withthe atmospheric-4
thereshouldnot bene needs
at themore
levelthanof 7x10
solar
oscillation
results
3 n’s
Þ Models developed with 1 or 2 sterile n’s

Signal : ne p→e+n np→d g(2.2MeV)

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.

MiniBooNE latest results
8GeVfromFNAL Booster

Mineral oilCherenkov• Significant low energy events excess (4.5 s)• They claim that the excess is due to the same oscillation
observed at the LSND.
• Concerns are

Neutrino2018
En-Chuan Huang– Systematic uncertainties (neutrino interactions, backgroundunderstandings)– Especially, unknown single gamma production events may
cause this.

• MicroBooNE can check the excess due to the gamma rayevents or electron antineutrinos.
6ne disappearance in reactor and b-source
Chris Polly, Thierry Lasserre
The Reactor Antineutrino Anomaly NEUTRINO2012
Ratio of Observed To Predicted Reactor-ν’sObserved/predicted averaged event ratio: R=0.927±0.023 (3.0 σ)

no oscillation
3 ν4 ν

Terra I ncognita
to be exploredReactor
Antineutrino
Anomaly (2011-)
ν-oscillation ?

Solar Neutrino
Anomaly(1968-2001)
ν-oscillation

Allowed(90%CL)

Atmospheric
Neutrino Anomaly(1986-1998)
ν-oscillation

Mention et al, 2011
Reactor – Detector Distance (m)High Dm2 ?
The Gallium Neutrino Anomaly The Anomalies
Th. Lasserre – Neutrino 2012

Test of solar neutrino detectors
GALLEX and SAGE (ve’s)

8Raghavan's idea

E ≈ MeV, Baseline range ≈ few m~3σ4 calibration runs
≈1 MCi EC νe emitters
Gallex51

P(ne→ne)ne disappearance
w/ reactors

Dm2>0.1, sin22q>0.05 → Losc = [1-10] m
10Recently,
they haveresults.

110102103104L (m)ne disappearance• Summary of the recent
results so far. (exciting!)

STEREO(BL 9-11m)
Jacob Lamblin’s talkin neutrino2018

NEOS (BL 24m)
PRL 118 (2017) 121802

Neutrino-4 (BL 7.3-11.1m)
arXiv:1809.10561

DANSS(BL 10.7→12.7m)
arXiv:1804.04046• Except for the neutrino-4
experiment, reactor experiments
show the null results.

PROSPECT (BL 6.7-9.2m)
arXiv:1806.02784

Current situation / what experimentalists should do• 3+1 oscillation model cannot explain all phenomena fromvarious experiments. (especially, disappearance measurements(nm→nm and ne→ne :except for Neutrino-4) and appearance
ones have a tension.)• If all are true, we absolutely need new physics model.
• Or experimental data is something wrong?? This part is being
and will be examined by experimentalists.
– MicroBooNE (running) / SBN (SBND+MicroBooNE+ICARUS) for MiniBooNE anomaly– JSNS2 for the LSND experiment– Many reactor experiments are on-going, thus they can check further.

Peter Wilson’s talk @ WINP workshop

3 LArTPC detectors(100-600tons)

Liquid Argon TPC

Ionization electrons• Principle

ElectricField– Quasi-free electrons from ionized tracks aredrifted.

Cherenkov light• Charge (MIP)〜1fC/mm (~5500e/mm)• drift velocity = 2m/ms @ 1kV/cm– Position information from2D (x,y) anode andtiming → 3D tracking w/ 1mm resol.
– No amplification from LAr (different from Gas Ar)

Chargedparticle• Features– LAr is cheap and high density material– LAr TPC has high tracking efficiency– Low energy threshold– PID by local dE/dx (each wire or strip)– Full sampling and homogeneous calorimeter• Advantages for physics

Scintillation lightpion

40 cm
positron– Multi-track meas. -> exclusive meas,proton
Test-Beam data
– Calorimetric energy measurement. (elastic events
0.8 GeV/cselection is unneeded.)
76 cm– Good e/p0 separation KEK LAr Group has own R&D activity independent from US/EU

Compared to MiniBooNE,
there is no p0 background
eventsMicroBooNE is running,and ICARUS is now at FNAL.
(SBN will start from 2020)

Neutrino2018
Roxanne Guenette

Status of ICARUS

Pictures from Yun-Tse Tsai’s slide in NuFACT2018 conference (Aug-18)(commissioning will be started soon, and data taking will be started by 2019-Sep)

Collaboration meeting @ J-PARC(2018/Jul)

JSNS2 collaboration (58 collaborators)• 6 Japanese institutions (28 members)• 10 Korean institutions (20 members)• 1 UK institution (3 members)• 5 US institutions (7 members)

Direct tests for LSND.

16

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)
1st 1MW trial
was succeededon July-3.

Materials and Life
Science Experimental
Facility (MLF)

CY2007 Beams
JFY2008 Beams
JFY2009 Beams

Hadron hall
Bird’s eye photo in January of 2008

J-PARC MLF：World best environment
MLF building (bird’s view)

Detector @ 3rd floor(24m from target)

Hg target = Neutronand Neutrino source

50t liquid scintillator detector(4.6m diameter x 4.0m height)
192PMTs
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

18

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+ Decayat-Rest➢ n from p and K -> removed with timing➢ Beam Fast neutrons -> removed w/ time
➢ Cosmic ray BKG -> reduced by 9ms timewindow.

➢ Energy: signals / BKG separation byenergy.

➢ n from m has well-known spectrum.
➢ Energy reconstruction is very easy at theIBD. (En ~ Evis + 0.8MeV)➢ n from m- is high suppressed.
19

Sensitivity of JSNS2

IceCube+SBL allowed (90%)
99% from arXiv 1607.00011v2

One detector x 3 years

Now requesting budget

5 years x MW x 2 detectors
20

Achievements so far• 2013 Sep; A proposal was submitted to the J-PARC PAC• 2014 Apr-Jul; We measured the BKG rate on 3rd floor.
-> manageable beam /cosmic BKGs to perform JSNS2PTEP 2015 6, 063C01 / arXiv:1502.02255• 2014-Dec; The result was reported to J-PARC PAC.
→ the stage-1 status was obtained from J-PARC/KEK• The performance check of detector and safety
discussions are being performed.
• 2016-June: The grant-in-aid is approved for one
detector construction• 2017-May: Technical Design Report was submitted
to J-PARC PAC and arXiv (arXiv:1705.08629[physics.ins-det] )• 2018-Sep: The stage-2 (real go-sign forexperiment) was recommended by PAC.
We aim to start JSNS2 in JFY2018, the detector
construction is on-going.

2014BU1301
experiment (@MLF 3rd floor)
Proton beam
Signal region forprompt signal
BKG ~ 021

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

Overall schedule
JFY2018
4-6
Acrylic Tank
production
PMT/acrylicinstallation

JFY2019
7-9

10-12

2019
1-3

4-6

7-9

Already under production

LSproductionDry run
FillingFirst
physics run
First beamoff
2nd runWe eager to start the experiment within this JFY to have good competitions, especially to SBN

10-Stainless tank construction• Construction at J-PARC (2017/Dec – 2018/Jan)• Welding, water leak test was done on 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 installation building.

2017/Dec/25

2018/Feb/28

23

Current status (1)PMT support structure

Reflection sheet• Cleaning inside of detector was done withpure water and ethanol.
• All pieces of materials were cleaned withultra-sonic machine with ethanol.
• Installation of PMT
support structure andreflector sheet wasdone.
• Installation of opticalseparator was done.
• PMTs will be ready inthe same timescalewith the acrylic tank.
PMT installation

PMT

24

Current status

Current status (2)Top lid part

• Currently, an acrylic tank and the pure-LSare being produced.
• Gd loaded LS (GdLS) will be donated byDaya-Bay experiment. (now at custom work)• A lot of other hardware / software are inprogress.
LS production @ Korea (RENO site)
21 batches in total (37000 L:)- 4 persons / day (shift)- 2 of ISO tanks

Acrylic tank production @ Taiwan (Nakano)support part

Summary• Confirming or refuting the existence of “Sterile Neutrino” is one ofhottest topics in the neutrino community in this 20 years.
• Many experiments are on-going or planned.
• There are a lot of interesting results from reactor experiments.
• Also nm disappearance experiments.
• Currently, results from disappearance experiments (except for Neutrino-4)
and results from LSND / MiniBooNE have a tension.

• SBN will start taking data soon. (including the running mBooNEexperiment)• JSNS2 experiment aims to start the experiment from JFY2018. This
experiment is a direct ultimate test for the LSND anomaly without any
excuses. (same neutrino source and neutrino target but improve S/Nby more than 100 and systematics)• New appearance experiments will have results soon. Enjoy!!

backup

Production / 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

Most of them
are same as
The LSND.
→ Direct ultimate
tests for LSND.

(Decay-at-Rest)
Scintillation lightp+

IBD criteria

TimingEnergyPrompt1<Tp<10μs

20<E<60MeV

DelayedTp<Td<100μs

7<E<12MeV<T>~30ms

Scintillation light(~ 8MeV In total)

But use muchbetter beam andGd loaded LS.
→ Much better
S/N→ Much bettersystematics
28

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 )Selection e~ 38%#events (1MW x 3 years x 1 detector (17tons))
Sourcecontents#ev.(17tons x 3years)

Reference : SR2014(50tons x 5 years)

comments

backgroundne 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

2032

Based on real data

87

480

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– SRprompt, SRdelay are probability of accidental BKG for prompt and delayed.
– DVTX ; BKG rejection factor of 50.
– Nspill(#spills / 5 years) = 1.9x109

30

Energy Spectrum and Sensitivity•••

Left: Energy spectrum; （Top: Dm2=2.5eV2, Bottom; 1.2eV2 sin22q =0.003)
Right: Sensitivity of 3 years physics running of JSNS2 with one detector.
We aim to start the one detector running from the end of JFY2018, andmeanwhile we also try to obtain budget for the second detector.
JSNS2ExploringRegion(90%)

31Movement to assembly building（2018/Mar/14)
Crane work

Around accelerator controlbuilding

Tank was put on the low bed Trailer

Shutter ofAssemblybuilding

Assembly building

Around Assembly building

The tank was moved for almost 2.2km.
322Other physics in JSNS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))
JSNS2 (arXiv:1601.01046)

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