Takashi IidaTakashi Iida(Queen’s University, Canada)(Queen’s University, Canada)

Mar. 21Mar. 21stst, 2011, 2011

Seminar @Gran Sasso National LaboratorySeminar @Gran Sasso National Laboratory

(Diffuse Supernova Neutrino Background : DSNB)(Diffuse Supernova Neutrino Background : DSNB)

About me!!About me!!

• Takashi IidaTakashi Iida• Ph.D with SRN search Ph.D with SRN search

in Super-Kin Super-K• Posdoc for SNO+ in Posdoc for SNO+ in

Queen’s university, Queen’s university, CanadaCanada

Ciao !!Ciao !!Thank you Thank you

for the invitefor the invite

OutlineOutline

• Introduction – Supernova and Supernova relic

• Experiments review– LSD, Super-K, SNO, KamLAND

• Future experiments– Gadzooks!, SNO+, LENA

• Summary

Supernovae have a historySupernovae have a history

People have been looking for Supernovae for more than 1000 years.

But,,,

SN 1006 remnantSN 1006 remnant

Astronomy is one of the oldest studyAstronomy is one of the oldest study

Supernovae have been happening since the Big bang!Supernovae have been happening since the Big bang!The history of SN is about 14 billion years!!The history of SN is about 14 billion years!!

What can we learn from SN??What can we learn from SN??• Neutrino oscillation• Neutrino mass hierarchy• MSW effect

• Cosmic rays• Gamma ray burst• Gravitational wave• Neutron stars, blackhole

• Nucleosynthesis • R-process• Neutrino process

Supernova!!Supernova!!

Particle Particle physicsphysics

AstrophysicsAstrophysics

Nuclear Nuclear physicsphysics

Understanding SN is Understanding SN is Very important !!Very important !!

24 years from SN1987A24 years from SN1987A

•Neutrinos are emitted from SN.•Luminosity. Order of 10^53 erg•Average E of neutrinos. ~10MeV•Duration of the burst. ~10sec

Feb. 23Feb. 23rdrd 1987 1987First neutrino First neutrino

detection from detection from Supernova!!Supernova!!

We learned from SN1987A We learned from SN1987A

the dawn of a new era in ”Neutrino astronomy”

It’s been two decades since 1989.

It’s been two decades since 1989.

This decade will be a great time

This decade will be a great time

for for “Neutrino Astronomy”!!

“Neutrino Astronomy”!!

We are all waiting for SNWe are all waiting for SN

• Understanding supernova burst is important for Understanding supernova burst is important for particle physics, nuclear physics and astrophysics.particle physics, nuclear physics and astrophysics.

• Neutrino is the best tool for observing SN Neutrino is the best tool for observing SN • Realtime SN is rare: Realtime SN is rare: < 1SN / 30y / galaxy < 1SN / 30y / galaxy • Supernova Relic Neutrino Supernova Relic Neutrino is stable and promising is stable and promising

sourcesource• Useful for studying Useful for studying SN mechanisms and evolution SN mechanisms and evolution

of the universeof the universe• No experiments has succeeded to detect SRN!!No experiments has succeeded to detect SRN!!

Krauss, Glashow, Schramm,Nature 310, 191 (1984)

Bisnovatyi-Kogan, Seidov,Sov. Astron. 26, 132 (1982)

Classic papers on SRNClassic papers on SRN

Supernova Relic NeutrinosSupernova Relic Neutrinos （（ SRNSRN ））

Supernova Relic NeutrinosSupernova Relic Neutrinos (SRN) are the Diffuse Neutrino (SRN) are the Diffuse Neutrino Background originate all the past supernovae.Background originate all the past supernovae.

There exist 10 ＾ 9 Galaxies and each has 10 ＾ 11 stars!! ~0.3% of them are big enough to make a Supernova explosion.In other words, 1010 ＾^ 17 Supernovae 17 Supernovae happened in our universe since Big ban.Each Supernova release 10^53 [erg]10^53 [erg] and 99% are emitted as neutrinos.

Red shift effect for Neutrino spectrum

S.Ando, Astrophys.J.607:20-31,2004.

Star formation rate measured by optics

Hopkins and Beacom, Astrophys. J. 651, 142(2006)

pastpresent

SRN shows us integrated SN neutrino from past to present.SRN shows us integrated SN neutrino from past to present.

Supernova Relic Neutrinos Supernova Relic Neutrinos （（ SRSRNN ））

What can we learn from SRN??What can we learn from SRN??

• The history of UniverseThe history of Universe• The history of heavy The history of heavy nucleosystheis.nucleosystheis.

• The mechanism of SupernovaThe mechanism of Supernova (Total/Average (Total/Average energy, energy, spectrum)spectrum)

• Invisible SN exist?Invisible SN exist?and so on…and so on…

C: Speed of lightC: Speed of lightZ: Red shift parameterZ: Red shift parameterFF: Flux of SRN: Flux of SRNEE: Energy of SRN: Energy of SRNConstant SN (Totani et al., 1996)

Totani et al., 1997Hartmann, Woosley, 1997Malaney, 1997Kaplinghat et al., 2000 Ando et al., 2005Lunardini, 2006 (dash)Fukugita, Kawasaki, 2003

Now we understand SRN is important!Now we understand SRN is important!But how to detect SRN??But how to detect SRN??

ScintillatoScintillatorr

WaterWater

We have two possible choices!!We have two possible choices!!

Large volumeLarge volume

Cheap and easyDirection informationSpallation (<18MeV)

Invisible -e decay from atmospheric (>18MeV)

Low BackgroundLow BackgroundLarge light yield (×100)

Neutron taggingNo inv-

Lower E thresholdReactor (<10MeV)

Atmospheric

So, what’s presented today?So, what’s presented today?

• This is the most important This is the most important plot in this talk !!plot in this talk !!

• Solid line shows the SRN flux upper limit from each experiment.

• Dashed line shows expected sensitivity for future experiments.

SNO+SNO+

LENA LENA

GADZOOKS!GADZOOKS!

• What they have already done?

• What limited the sensitivity so far?

• Can we improve more for future?

are presented!!

(Ando model)

SRN search so farSRN search so far

• Kamiokande (1988)Kamiokande (1988)• LSD (1992)LSD (1992)

• Super-K (2003)Super-K (2003)• SNO (2007)SNO (2007)

• KamLAND (2008)KamLAND (2008)

Kamiokande detector and analysis are similar to Super-K.Kamiokande detector and analysis are similar to Super-K.So please let me skip Kamiokande and explain detail for Super-K.So please let me skip Kamiokande and explain detail for Super-K.

LSDin Mont-Blanc Laboratory

Detection of SRN in LSDDetection of SRN in LSD

All fravor via NCAll fravor via NC

ee and and ee via CC via CC

ee via Inverse beta decay (IBD) via Inverse beta decay (IBD)

2.2MeV2.2MeV

SRN search in LSDSRN search in LSD

• The energy threshold is set at 5MeV for inner 16 counters and 7MeV for external ones.

• After each trigger the energy threshold is lowered to 0.8MeV for 500 sec to detect gamma ray.

• Detection efficiency of delayed gamma is 50%.

Energy spectrum of IBD like eventEnergy spectrum of IBD like event

• Energy spectrum. • One event between

12-25MeV. Nlimit = 3.8 @90%

C.L.

All events

Followed by 2.2MeV

Result in LSDResult in LSD

• This is the first result for all flavor neutrinos.• Although worse than Kamiokande.

Mont-Blanc LSD result (1992)Mont-Blanc LSD result (1992)

e

(Ando model)

Super-K detectorSuper-K detector

• 50,000 ton total mass• 22,500 ton fiducial volume22,500 ton fiducial volume• 11,146 50 cm PMTs Inner11,146 50 cm PMTs Inner• 1,885 20 cm PMTs Outer• 40% photocathode coverage• 1000 m minimum depth1000 m minimum depth• 4.5 MeV Trigger threshold• E Res. 16%/E1/2 @ 10 MeV• Position ~50 cm @ 10 MeV• Angular ~30° @10 MeV

42 m

39.3 m1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007…

AccidentSK-I SK-II SK-IIIFull reconstruct

Reconstruction

Super-K is a large water Cherenkov detector for detection experiment. It is located at Kamioka mine in Japan.

SRN detection in Super-kSRN detection in Super-k

Electron energy [MeV]

10

0.1

10-3

10-5

10-7

Enen

t Rat

e [/

year

/M

eV/2

2.5k

t]0

10 20 30 40 50

νe+ p e+ + n

νe+ 16O 16N + e+

νe+ 16O 16F + e-

νe+ e νe + e-

νe+ p e+ + n

Expected number SRN eventsExpected number SRN events0.3 -1.9 events/year/22.5kton

(Ee=18-30MeV)

Ee = E - 1.3 [MeV]

Inverse beta decay is dominant reaction in Super-K

Background SourcesBackground Sources

5, 「 Imvisible 」 -e decay from atmospheric 6, Atmospheric e

（１）ー（４） is rejected by data analysis （ Next page ）

（５）、（６） is considered by spectrum fitting ( later)

cf. 「 visible 」 means that muon E is over the Cherenkov threshold

1, Cosmic ray muon 2, Spallation induced by cosmic ray muon3, Solar neutrino4, 「 Visible 」 -e decay from atmospheric

Normal Spallation cutNormal Spallation cut

Tight Spallation cutTight Spallation cut

Cherenkov angle cutCherenkov angle cut

Solar direction cutSolar direction cut

The spallation BGThe spallation BG is reduced by a likelihood method that uses timing is reduced by a likelihood method that uses timing and track information of the muons preceding the candidate events.and track information of the muons preceding the candidate events.

Positrons with E>18MeV have a Cherenkov angle of Positrons with E>18MeV have a Cherenkov angle of CC ~ 42 degrees. ~ 42 degrees. To remove To remove muons and multiple gamma-raysmuons and multiple gamma-rays, remove events with , remove events with 38° 38° < < C C or 50°or 50°CC..

To remeve To remeve solar neutrino eventssolar neutrino events, the events in the direction of the , the events in the direction of the sun are removed. (sun are removed. (E<25MeV && CosE<25MeV && Cossun sun >0.75>0.75))

In addition to the normal spallation cut, tighter criteria is applied in In addition to the normal spallation cut, tighter criteria is applied in order to enhance the rejection efficiency of order to enhance the rejection efficiency of spallation BGspallation BG. So, we . So, we remove events which occur within 0.15 secremove events which occur within 0.15 sec..

Gamma ray cutGamma ray cutSome Some ray events ray events originating from outside of fiducial volume have originating from outside of fiducial volume have possibility of being reconstructed within fiducial volume of SK. We remove possibility of being reconstructed within fiducial volume of SK. We remove the events whose expected travel distance of the events whose expected travel distance of ray is < 450cm ray is < 450cm..

Signal extractionSignal extractionM.Malek et.al. Phys. Rev. Lett. 90, 061101, 2003

Chi2 fitting using energy spectrum was done for extracting signal.

i systematicMCdata

relicdata iNiNiNiNe

222

22

)()()(()(

spectrumcatmospheriiN

spectrumcatmospheriiNspectrumMCSRNiNspectrumDatarealiN

e

relic

data

e

:)(

:)(:)(:)(

SK1 SK1 1496days1496days

Flux limit @90%C.L.Flux limit @90%C.L.< 1.2 /cm2/sec (>19.3MeV)< 1.2 /cm2/sec (>19.3MeV)

World best limit so World best limit so far!!far!!

Data

Atmospheric Atmospheric ee

Invisible Invisible -e decay-e decay( )

Latest official resultLatest official result

Visible energy [MeV]

SK-ISK-I

Visible energy [MeV]

SK-IISK-II

DATADATA

Atmospheric Atmospheric ee Atmospheric Atmospheric ee

Imvisible Imvisible -e decay-e decay

Imvisible Imvisible -e decay-e decay

Spallation BGSpallation BG

DATADATA

(1496day) (791day)

preliminarypreliminary preliminarypreliminary

90% C.L. Flux limit (preliminary)90% C.L. Flux limit (preliminary)SK-I : < 1.25 /cmSK-I : < 1.25 /cm22 /sec /sec

SK-I + SK-II : < 1.08 /cmSK-I + SK-II : < 1.08 /cm2 2 /sec/secSK-II : < 3.68 /cmSK-II : < 3.68 /cm22/sec/sec

Minor improvement of BG reduction & SK-II data added in 2007 Minor improvement of BG reduction & SK-II data added in 2007

Super-K resultSuper-K result

e

e

(Ando model)

SNO

306 days’ 1st phase data was used for this search

ee search search

SRN analysis in SNOSRN analysis in SNO• From1999 Nov. 2 until 2001 May 28 (306.4 days)

corresponding to an exposure of 0.65 ktons yr• Only single electron events are selected CC• 94% efficiency for SRN signal

SNO analysisSNO analysis

SRNSRN

Atm Atm

hephep

8B8BBG are estimated by atmospheric MC (Bartol04 flux and NUANCE package).0.18 +/- 0.04 0.18 +/- 0.04 BGs are expected.Mainly atmospheric NC.No BG observed in Evis = 21 – 35MeV!!

2.3 ev upper limit is set at the 90% CL.

Flimit < 70 /cm2/secFlimit < 70 /cm2/sec(E(E = 22.9 – 36.9MeV) = 22.9 – 36.9MeV)

SNO result (2005)SNO result (2005)

e

e

(Ando model)

The KamLAND Detector

PMT (225 20” in OD +

1879 17” and 20” in ID)

(34% coverage of ID)

Target LS Volume

(1 kton, 13m diameter)

80% Dodecane(C12H26)

20% Pseudocumene(C3H9) PPO

1.36g/l Buffer Oil Zone

Outer Detector (3.2 kton Water Cherenkov)

calibration device & operator

Stainless Steel Inner Vessel (18m

diameter)

Glovebox

Balloon & support ropes

Chimney (access point)

e search as like LSD and Super-K. νe+ p e+ + n

O.Perevozchikov

High Energy Candidates 6.0m fiducial volumeHigh Energy Candidates 6.0m fiducial volume7.5->15MeV:

10 candidates has been selected

+2 triple coincidence:

multiple neutrons capture

Run# 1824, Prompt# 13658585

Delayed# 13658586, 13658587

Run# 5941, Prompt# 4644789

Delayed# 4644790, 4644791

+1 muon decay

(triple coincidence)Run# 5380 Prompt_1#

41470(muon, E=15.5MeV)Prompt_2#

41471(positron, E=13.6MeV)

Delayed# 41472dT1-2=1.23μsecdR1-2=6.4 cm

Eprompt Edelayed

ΔTΔR

solar antineutrino energy range

▬ solar candidates▬ multiple n-capture

▬ μ - decay

▬ solar candidates▬ multiple n-capture

▬ μ - decay

▬ solar candidates▬ multiple n-capture

▬ μ - decay

▬ solar candidates▬ multiple n-capture

▬ μ - decay

10 events

6 events

10 events in 6.0m volume, 6 events in 5.5m 10 events in 6.0m volume, 6 events in 5.5m volume.volume.

Background sources in KamLANDBackground sources in KamLAND

• Accidental Background

• 9Li produced by cosmic muons

• Reactor antineutrinos

• Background from atmospheric neutrinos

Background estimationBackground estimationKamLAND 5.5m analysisKamLAND 5.5m analysis

•NC cross-section uncertainty 18%•Atmospheric neutrino flux uncertainty 22% •Combined uncertainty 28.4%

Total BG within 7.5-15MeV: 8.78 ± 2.16 events

Total BG within 15-30MeV:3.96 ± 1.04 events

protons

limit

NTN

e

Nlimit : number of limit @95% CL by F-C. : Averaged cross section : Detection efficiencyT : Livetime (1430d)Nprotons : Number of protons

120 /cm2 /sec (7.5-15MeV) 16/cm2 /sec /MeV

Oleg PerevozchikovHEP Seminar at BNL, Sep. 2009

KamLAND result (2008)KamLAND result (2008)

(Ando model)

Atmospheric neutrino BGs in KamLANDAtmospheric neutrino BGs in KamLANDKamLAND analysis also showed the event rates in future LENA,50 kt

liquid scintillator detector from the various neutrino sources (LENA proposal Phys.Rev.D75:023007)

Our B.G. calculations

They said:B.G. rate from NC interactions of the atmospheric neutrinos is

significantly higher than expected SRN…

Is that true!?Is that true!?

Can’t we detect SRN in future detector?

Can’t we detect SRN in future detector?

Let me discuss about this!

Let me discuss about this!

DiscussionDiscussion

• For a scintillator detector, atmospheric is the largest BGs ( + 12C + n + 11C).

• According to KamLAND analysis, this BGs are more significant than SRN flux.

• The key of BG reduction is 11C (~20min half life) tagging!!

Can we really defeat BG !?

Can we really defeat BG !?

11C tagging11C tagging

11C rate in KamLAND11C rate in KamLAND~1000 /day/kton ~1 [/day/m3]

11C search inside 1m sphere 1m sphere for 2hours2hours after SRN candidate

0.35 11C is expected in KamLAND0.35 11C is expected in KamLAND 35% inefficiency for SRN35% inefficiency for SRN

If we want to tag 11C, one order lower muon rate is required!!If we want to tag 11C, one order lower muon rate is required!!

15cm vertex resolution in LS detector @1MeV15cm vertex resolution in LS detector @1MeV20min half life of 11C20min half life of 11C

Enemy : + 12C + n + 11C

Deeper than Deeper than ~4000mwe ~4000mwe is preferableis preferable

Future experimentsFuture experiments

Gadzooks! / SNO+ / LENAGadzooks! / SNO+ / LENA

Gadzooks!Gadzooks!

• e signal can be separated from BG by neutron tagging.• Load Gd into SK water to detect gamma by neutron capture.

e

e+

pn

Gd

8MeV

Gd in water

0123456789

10

10 15 20 25 30 35 40 45 50

relic+B.G.(inv.mu 1/5)

B.G. inv.mu(1/5)atmsph.–e

Visible energy (MeV)

even

ts/10

years

/2Me

VPossibility of SRN detection

Relic model: S.Ando, K.Sato, and T.Totani, Astropart.Phys.18, 307(2003) with NNN05 flux revision

If invisible muon background can be reduced by neutron tagging

Assuming invisible muon B.G. can be reduced by a factor of 5 by neutron tagging.

With 10 yrs SK data,Signal: 33, B.G. 27(Evis =10-30 MeV)

SK10 years (=67%)

Assuming 67% detection efficiency.

Test tank for feasibility study is

Test tank for feasibility study is

now being constructed!!

now being constructed!!

Slide by M.Nakahata

Evaluating Gadolinium’s Action on Detector Systems

L.Marti in NOW2010

Tank was constructed.Mounting PMTs

Tank was constructed.Mounting PMTs

and installing electronics and DAQ.

and installing electronics and DAQ.

Aim to start within 2011.

Aim to start within 2011.

L.Marti in NOW2010

SNO+SNO+

SNO+ advantageSNO+ advantage

• Size Size - - SNO+ has 780 tons of scintillatorSNO+ has 780 tons of scintillator,,

comparing to 300tons of Borexinocomparing to 300tons of Borexino..• DepthDepth - - SNO+ is at 6080 mweSNO+ is at 6080 mwe, while, while KamLAND is at KamLAND is at

2700 mwe.2700 mwe.• Light yieldLight yield - - ~9500 PMTs. ~500 pe / MeV~9500 PMTs. ~500 pe / MeV - - Without Nd loading Without Nd loading 5% resolution @1MeV 5% resolution @1MeV

BG estimationBG estimationKamLAND analysis

Reactor flux 1/49Li negligibleAtm same rate

(tag 11C)

Assuming…

Total expected BGTotal expected BG1.07 BGs

(1430d, 7.5-15MeV)

Main BG source : + 12C + n + 11C 20min life time20min life time

Tagging 11C can reduce the atmospheric Tagging 11C can reduce the atmospheric BGs dramatically. BGs dramatically.SNO+ BG rate is less than 1/8 of KamLAND!!SNO+ BG rate is less than 1/8 of KamLAND!!

BG estimationBG estimationKamLAND analysis

Reactor flux 1/49Li negligibleAtm same rate

(tag 11C)

Assuming…

Total expected BGTotal expected BG0.3 BGs

(1430d, 7.5-15MeV)

Main BG source : + 12C + n + 11C 20min life time20min life time

2nd BG source : Reactor 3rd BG source : + p + n

E threshold E threshold detection effdetection eff

Flux limit on SRNFlux limit on SRN

protons

limit

NTN

e

Nlimit : number of limit @90% CL by F-C. : Averaged cross section : Detection efficiency (assume 90%)T : Livetime (5y)Nprotons : Number of protons in SNO+

(=7*10^31 protons)

26 /cm2 /sec (7.5-20MeV) 2.1 /cm2 /sec /MeV

18 /cm2 /sec (7.5-20MeV) 1.4 /cm2 /sec /MeV

For 1.07 BG

For 0.3 BG

SNO+ sensitivitySNO+ sensitivity

SNO+ 90%SNO+ 90%

(Ando model)

LENA

LENA sensitivityLENA sensitivity

SNO+SNO+

LENA ?LENA ?

Same BG level as SNO+Same BG level as SNO+Scaled by volume.Scaled by volume.

(50times bigger than SNO+)(50times bigger than SNO+)

3.7 /cm2 /sec (7.5-20MeV) 3.7 /cm2 /sec (7.5-20MeV) 0.3 /cm2 /sec /MeV 0.3 /cm2 /sec /MeV

(Ando model)

SummarySummary

• Supernova Relic Neutrino is the Diffuse Neutrinos from all the past supernovae.

• Several neutrino experiments tried to find it but no one has succeeded yet.

• Super-K limit (<1.2 /cm2/sec) is the world best published result.

• Future experiments are being prepared (Gadzooks!, SNO+ and LENA)

At the end At the end

• CDMS experiment observed "two" dark matter CDMS experiment observed "two" dark matter candidates with 0.9+/- 0.2 BGs expected.candidates with 0.9+/- 0.2 BGs expected.

• SNO+ may be able to detect about ”two” SRN SNO+ may be able to detect about ”two” SRN candidate with 0.5 expected BGs! candidate with 0.5 expected BGs! (5y, Ando model)(5y, Ando model)

• More SRN events will be detected in LENA!!More SRN events will be detected in LENA!!• For detecting SRN, understanding BGs is crucial.For detecting SRN, understanding BGs is crucial.• If you're interested in BG study for SRN search, If you're interested in BG study for SRN search,

let’s work together!!let’s work together!!

• Backup slide

Atmospheric : + p + + nSpallation : 9Li + n decay

Irreducible BG in Gadzooks! Irreducible BG in Gadzooks!

μ

O

e

γ

X

Xe

Spallation product is made by cosmic ray muon. Some of spallation products can be a BG for SRN search.

List of possible spallation productsList of possible spallation products

Main BG in Super-K Main BG in Super-K below 18MeVbelow 18MeV

SpallationSpallation

Spallation like events are removed using a position and timing information with preceding muons.

Remaining BGRemaining BG

この、

は現在のところデータ解析による除去が出来ない。

大気ニュートリノの「見えない」ミューニュートリノから大気ニュートリノの「見えない」ミューニュートリノからの崩壊電子の崩壊電子 大気ニュートリノの電子ニュートリノ成分　大気ニュートリノの電子ニュートリノ成分　 (( 大気大気 e)e)

'

'

NeN

ethresholdcherenkovbelow

NN

e

e

BGBG スペクトルの形状を見積もって、データに対してフィッティスペクトルの形状を見積もって、データに対してフィッティングを行うことで、ングを行うことで、 SRNSRN シグナルを探す。シグナルを探す。

( Invisible ( Invisible e decay e decay

Fitting に用いるスペクトルは、 invisible m-e decay に関しては、データドリブンで、宇宙線宇宙線 stoppingstopping からの崩壊電子スからの崩壊電子スペクトルペクトルを用い、大気 e にはデータがないので、大気大気 MCMC を用いる。

0

0.5

1

1.5

2

2.5

3

3.5

4

Constant SN rate

(Totani et al. 1996)

Totani et al. 1997

Malaney et al. 1997)

Hartmann et al. 1997)

Kaplinghat et al. 2004

Ando et al. 2005

Fukugita et al. 2003

Lunardini et al. 2006

SK-II limit = 3.68 /cm2/sec

SK-I limit = 1.25 /cm2/sec Combined limit = 1.08 /cm2/sec

preliminary(E>18MeV)

Super-K flux limit VS predicted fluxSuper-K flux limit VS predicted flux/cm2/sec

Now, Super-K limit is close to model prediction!!Now, Super-K limit is close to model prediction!!

Background in Super-KBackground in Super-K

ReactorReactor

Invisible Invisible SpallationSpallation

At the end At the end

• CDMS experiment observed "two" dark matter CDMS experiment observed "two" dark matter candidates with 0.9+/- 0.2 BGs expected.candidates with 0.9+/- 0.2 BGs expected.

• SNO+ may be able to detect about ”two” SRN SNO+ may be able to detect about ”two” SRN candidate with 0.5 expected BGs! candidate with 0.5 expected BGs! (5y, Ando model)(5y, Ando model)

• More SRN events will be detected in LENA!!More SRN events will be detected in LENA!!• For detecting SRN, understanding BGs is crucial.For detecting SRN, understanding BGs is crucial.• If you're interested in BG study for SRN search, If you're interested in BG study for SRN search,

let’s work together!!let’s work together!!

Hano-Hano

BG estimationBG estimationKamLAND 5.5m analysis

Reactor flux 1/49Li negligibleAtm same rate

Assuming…

Total expected BGTotal expected BG4.8 BGs4.8 BGs

(1430d, 7.5-15MeV)

Main BG source : + 12C + n + 11C

LAB AdvantagesLAB Advantages• compatible with acrylic, undiluted• high light yield (because it’s undiluted)• pure

– light attenuation length in excess of 20 m at 420 nm

• high flash point (130°C) safe• low toxicity safe

• LAB used as the feedstock to make LAS, a common ingredient in household detergent

• low cost (relative to other organic solvents)• smallest scattering of all scintillating solvents investigated• Petresa Canada plant in Quebec makes 120 kton/year

• Double CHOOZ, Daya Bay, Hanohano, LENA, NOA and others are now also looking at LAB as a scintillator

11

0pseudocumene (2 4 0)diesel (0 2 0)

How to detect SRN??How to detect SRN??

Water detectorWater detectorScintillator detectorScintillator detector

Large volumeLarge volume

Cheap and easyDirection

Spallation (<18MeV)Invisible mu from

atmospheric n (>18MeV)

BG reductionBG reductionLarge light yieldNeutron tagging

No inv-mLower E thresholdReactor (<10MeV)

Atmospheric n

Detection in SNO+Detection in SNO+

Super-K (HSuper-K (H220)0)

SNO (DSNO (D22O)O)

Kamioka Liquid-scintillatorAnti-neutrino Detector (KamLAND)

Inside the Kamioka Mine

Surrounded by 55 Japanese Reactor Units

Detecting reactor e 1km beneath Mt. Ikenoyama-