Sterile Neutrino Searchin the JSNS2 Experiment

Soo-Bong Kim(Seoul National University andTomonaga Center for the History of the Universe)

TCHOU seminarJan. 19, 2018

Dark World

Strong gravitational lensing by HST
in Abel 1689

WMAP 2008

Neutrino Oscillations and Mass
“Established three-flavor mixing framework”
Atmospheric
Neutrino Oscillation(1998)

q23

Solar Neutrino
Oscillation(2001)

q12

Reactor Neutrino
Oscillation(2012)

q13“Neutrino has mass”
 Right-handed sterile neutrino?

Coupling between SM and Dark Worlds
Hidden Sector : sterile particles as SM singlets

Mixing with Sterile Neutrinos?
 If mixing between
and chance for neutrino oscillation with Dm2 ~1 eV2 Sterile neutrinos , which interact withthe gravity only, may be indirectly
observed by neutrino oscillation
because of a possible mixing due to.

F. Suekane

Hints for Sterile Neutrino Search Anomalies that cannot be explained by standard neutrino
oscillations, but tension with null results in disappearance
Experiments

Neutrino source

signalsignificanceE(MeV),L(m)LSND

m Decay-At-Rest

nm  ne3.8s

40,30MiniBooNE

p Decay-In-Flightnm  ne

3.4s

800,600

nm  ne2.8s

combined

3.8s

Ga (calibration)e capturene  nx

2.7s<3,10Reactors

Beta decayne  nx

3.0s

3,10-100

 Needs repeat of the LSND measurement using an identicalneutrino beam (DAR) and the same detection method (IBD)with better sensitivity.

LSND ExperimentLSND Results
1998(1990-1995, 1997-1999)

MiniBooNE ResultsReactor Anomaly

Sterile Neutrino Oscillation

Yufeng Li

Sterile Neutrino Oscillation
Null results ondisappearance

Yufeng Li

JSNS2(2019)(2015)(2018)

Future Sterile Neutrino Search(Reactor/b/Source Exp.)

Yufeng Li

Future Sterile Neutrino Search

Yufeng Li

JSNS2 Experiment(J-PARC Sterile Neutrino Searchat J-PARC Spallation Neutron Source)JSNS2 Collaboration
JAEA
KEK
Kitasato
Kyoto
Osaka
TohokuSoongsilDongshin
GIST
Seoyeong
Chonnam
Seoul

Chonbuk
Kyungpook
Sungkyunkwan
SeoulTECH
sci and tech

Alabama
BNL
FloridaMichigan

SussexWhy JSNS2 ?
 Direct test of the LSND with better sensitivity- Muon antineutrino beam from muon Decay At Rest (DAR) Narrow (~9 ms) pulsed (every 40 ms) neutrino beam at JPARC MLF :(vs. continuous beam used by LSND)- Pure muon decay at rest
- Narrow timing window for cosmic ray rejection- No decay-in-flight source- No beam induced fast neutrons

 Improved detector :- Gd doped LS significant reduction of backgrounds by a tighter (~1/6)
time coincidence and a higher (2.2  8 MeV) delayedenergy

JSNS2: J-PARC E56
Sterile n search@MLF
http://research.kek.jp/group/mlfnu/eng

400MeV

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

3 GeV RCS

Neutrino Beams(to Kamioka)

25Hz, 1MW (design)

Materials and Life
Science Experimental
Facility (MLF)

CY2007 Beams
JFY2008 Beams
JFY2009 Beams

Hadron hall
Bird’s eye photo in January of 2008

JSNS2 Experiment at J-PARC MLF

MLF building (bird’s view)

Detector @ 3rd floor(24m from target)

Hg target = Neutron
and Neutrino source

17t Gd-loaded liquid scintillator /detector (total 50tons/detector)(4.5m diameter x 4.0m height)
193PMTs

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

Neutrino Source: Mercury Target at MLF
 World-class high intensity neutron source driven byhigh power proton beam
- beam energy: 3 GeV- design beam power: 1 MWNeutrinos from Muon Decay At Rest (DAR)

(1)
(3)

(2)

μs

Advantages of JSNS2 DAR Neutrino Beam

Timing and Energy of Neutrino Beam
Timing and Energy are good 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.

Pulsed Neutrino Beam

Selecting muon decay(e~74%)

Neutrino Spectra from DAR+Decay in FlightPure Muon Antineutrino Beam
 t > 1 ms after arrival of a beam
 choose neutrinos from m decay suppress beam backgrounds

Oscillation Signature of Muon Antineutrino

Neutrino 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(Decay-at-Rest)
Scintillation lightp+

IBD criteria

TimingEnergy

Prompt1<Tp<10μs

20<E<60MeV

DelayedTp<Td<100μs

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

Scintillation light(~ 8MeV In total)

30

Event Selection for Electron Antineutrinos

Signal Extraction & Sensitivity

3 years x MW x 17 tons
x 50 tons

History and Plan of JSNS2
 Sep 2013: Submitted a proposal to J-PARC PAC
 Apr-Jul 2014: BG rate measurement at MLF 3rd floor Dec 2014: Submitted a status report on BG results
 Jan 2015: Stage-1 approval from J-PARC PAC
 Jun 2016: Funding approval for the first detection
construction
 Jan 2017: Participation of Korean group
 May 2017: Submitted a TDR to J-PARC PAC to request
stage-2 approval Nov 2017: Submitted a revised TDR to the PAC forstage-2 approval Jan 2018: SUS tank under construction
 Early 2019: Will start data-taking

On-site Background Measurement (2014)

Technical Design Report to PAC

JSNS2 Detector

Schedule for 1st Detector Construction

Korean group

SUS Vessel at J-PARC

LS Production at RENO

Low Energy Neutrino Beam
Energy Spectra of Decay-At-Rest nSN-nDAR-nLuminosity (×1051 erg/s)

3.5νμνe3νeνe

2.5

νμ21.510.50νμ, νμ, ντ, ντ0102030
40
50Energy (MeV)

607080Neutrino-nucleus Interaction in Type-II SN

Thanks for your attention!