supernova neutrinos in sk-gd and other experiments€¦ · pre-supernova at 200pc hiroyuki sekiya...

Hiroyuki Sekiya NEUTRINO2016 London July 9 2016

tSupernova neutrinos in SK-Gd

and other experimentsNEUTRINO2016 @LONDON

JULY 9 2016

Hiroyuki SekiyaICRR, University of Tokyo

for the Super-K Collaboration

Total 24 pages


Supernova neutrinos from 1987A The only detected SN neutrinos are from LMC(50kpc)

2

Kamiokande-II (11 evts.)IMB-3 (8 evts.)Baksan (5 evts.)

Jegerlehner, Neubig & Raffelt, PRD 54 (1996) 1194

Total energy

released by ν̅e: ~5x1052 erg

24 (ν̅e ) events in total.

The obtained binding energy is almost as expected, but large error in neutrino mean energy. No detailed information of burst process.

We need energy, flavor and time structure.


Many models… Need data!Figures: H.Suzuki, M. Nakahata

3

“Livermore”as a reference

“Nakazato”as a reference


Detectors that observed 1987A

4

Kamiokande-II◦ 2140 ton FV◦ Water Cherenkov◦ > 8.5MeV

Essentially, inverse beta decay events.

BAKSAN◦ Total 330ton ◦ Liquid Scintillator◦ > 10 MeV

IMB-3◦ ~5000 ton FV◦ Water Cherenkov◦ > 28 MeV

SNOwGLoBES http://www.phy.duke.edu/~schol/snowglobes/


The current water detector Super-Kamiokande

◦ 32k ton FV > 4.5 MeV(kin)◦ 8.8k ton FV > 3.5MeV(kin)

5

Livermore Nakazatoν̅ep e+n 7300 3100ν+e- ν+e- 320 17016O CC 110 57

Supernova at 10 kpc# events in 32kton SK volume

Pointing accuracy ~5°

Livermore: ApJ.496,216(1998)Nakazato: ApJ.Suppl. 205 (2013) 2

Angular distributions

May help large optical telescopes.

20Msun, trev=200msec, z=0.02


Water detectors provide high statistics

ICECUBE◦ Giga-ton◦ By increase of PMT single rates, fine

time structure is obtained.

6

Time variation of mean energyTime variation of event rate

IceCube collaboration,A&A 535, A109 (2011)

Super-Kamiokande (cont’d)

Enough statistics to discriminate models!Supernova at 10 kpc


Current liquid scintillators KamLAND

◦ 1kton

7

LVD◦ 1kton

Borexino◦ 320 ton

NOvA◦ 14k ton

BAKSAN◦ 330 ton

Daya bay◦ 20 ton x 8 (SNO+)

◦ 1k ton


Liquid scintillators KamLAND

◦ Low threshold o(100keV)◦ Sensitive to Si burning phase. KamLAND send pre-SN alarm <700pc

8

Livermore

νe̅p e+n 300

ν+e- ν+e- 20

ν+p ν+p 30012C CC 60

Pre-SN ν

Reactor ν

Geo-ν

Time evolution Odrzywolek 2010, Nakazato 2012

Pre-SN

Supernova at 10 kpc

SN, t=0

IshidoshiroPre-supernova at 200pc


Kate Scholberg Neutrino2014

9

Supernova-relevant neutrino interactionsElectrons Protons Nuclei

Chargedcurrent

Elastic scattering

Usefulfor pointing

Inverse beta decay

Neutralcurrent

Elasticscattering

γ

γe+

nνe

γ

ν

e-

νe

e-e+/-

νe

γ n

γVarious possibleejecta anddeexcitationproducts

Coherentelastic (CEνNS)

νγ n

γν

Aνp

very low energyrecoils


Nuclei targets HALO

◦ 79 t of Lead◦ SNO’s 3He counter◦ polypropylene tubes for n moderation

10

reaction neutrons

CC 1n 30

CC 2n 19x2

NC 1n 8

NC 2n 6x2

n + 3He → 3H + p + 764 keVNot sensitive to e-, no NC/CC discrimination

νe + 208Pb → 207Bi + n + e-

νe + 208Pb → 206Bi + 2n + e-

νx + 208Pb → 207Pb + nνx + 208Pb → 206Pb + 2n

CC NC ES

Supernova at 10 kpcA Habig

~50% of detection efficiency~40 events are expected

(ICARUS) ◦ Ar-TPC 600t ◦ LGNS→FNAL

νe + 40Ar → 40K* + e-

ν̅e + 40Ar → 40Cl* + e+

νx + 40Ar → νx + 40Ar* νx + e- → νx + e-

Livermore

νe + 40Ar 40

ν̅e + 40Ar 3

νx + e- 5

Supernova at 10 kpc

Unique sensitivity to νe

Possibility to separate channels by the associated deexcitation

Scaled from Inés Gil-Botella’s DUNE value


DM detectors Coherent elastic neutrino-nucleus scattering

LUX◦ Xe 0.37 ton FV

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XMASS◦ Xe 0.83 ton FV in 800t water◦ >300eV◦ SK GPS ◦ KamLAND

Pre-alarm

Xe

CEνNS cross section

Ar

P. C. Divari High Energy Phys. (2012) 379460

Supernova at 10 kpc

CEνNSev

ents

/10s

ec

XMASS BGSupernova at 200 pc

Livermore

ν+Xe ν+Xe 15

Livermore

ν+Xe ν+Xe 3.9x104

(DEAP3600)◦ Ar 3.6 ton FV

XENON1T◦ Xe 1 ton FV

K. Hiraide


Super-KamiondeEGADSKamLAND-ZenXMASS

LVDBorexinoXENON1T

Baksan

IceCube

DayaBay

NOvA

SNO+HALODEAP3600

LUX

Supernova neutrino detectors

Antares


Larger detectors in future

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DUNE◦ 40kton Ar TPC

IceCube-Gen2/PINGUKM3NeT Phase-2.0/ORCA

JUNO / RENO50◦ Liq. Sci ~20kton

Tamborra et al.,PRD 90 045032 (2014)

Supernova at 10 kpcSASI observation!

Supernova rate based on 2000-2011Horiuchi et al., ApJ. 769 (2013) 113

Hyper-K 0.38MtonDetection Probability

Hyper-Kamiokande◦ 0.5 Mton, 0.38 Mton FV◦ 0.2~3.3 SNe in 10 years(N>2)

Extend detection reach to 10 Mpc!


Extend to whole universe… DSNB (SRN) 1010 stellar/galaxy ×1010 galaxies ×0.3%(become SNe) ~O(1017)SNe

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Beginning of the universe

NOW

１billion years ago

10 billion years ago

Neutrinosfrom past SNe

Horiuchi, Beacom and Dwek, PRD, 79, 083013 (2009)

Search window for SK : From ~10MeV to ~30MeV


Status of DSNB search

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Comparison with expected ν̅e signal

Limited by BG. More than 1 order reduction is needed.◦ n tagging efficiency (by proton) is low…

Theoretical flux prediction : 0.3~1.5 /cm2/sCurrent best limit by SK: 2.8~3.1 /cm2/s

(>17.3MeV)


SK-Gd project Identify νep events by neutron tagging with Gadolinium. Large cross section for thermal neutron (48.89kb) Neutron captured Gd emits 3-4 γs in total 8 MeV Gd2(SO4)3 was selected to dissolve.

16

Beacom and Vagins PRL93,171101 (2004)

Cap

ture

s on

Gd

Gd in Water

100%

80%

60%

40%

20%

0.0001%0.001% 0.01% 0.1% 1%

0.1% Gd (0.2% in Gd2(SO4)3) gives~90% efficiencyfor n capture

0%

In Super-K this requires dissolving ~100 tonsof Gd2(SO4)3


BG source: atmospheric neutrino CC

17

Invisible μ n + decay-e

（anti-）νe CC

μ generation

νe e

νμ μ eT < 50 MeV

“invisible muon”

νμ μ

n

n

n

NCNC elastic de-excitation γ

νx νx

16O* → γn

Total energy MeVN.B. Vertex information gives further BG reduction

even

ts/y

ear/

1.5M

eV

Expected BG rate

νe CCνµ CC

NC elastic


Expected signal

It depends on typical/actual SN emission spectrum

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Total (positron) energy MeV

even

ts/y

ear/

1.5M

eV

DSNB flux:Horiuchi, Beacom and Dwek, PRD, 79, 083013 (2009)

Expected total BGTν = 6MeVTν = 4MeVTν = 1987a

HBDmodels

10-16MeV(evts/10yrs)

16-28MeV(evts/10yrs)

Total(10-28MeV)

significance(2 energy bin)

Teff 8MeV 11.3 19.9 31.2 5.3 σ

Teff 6MeV 11.3 13.5 24.8 4.3 σ

Teff 4MeV 7.7 4.8 12.5 2.5 σ

Teff SN1987a 5.1 6.8 11.9 2.1 σ

BG 10 24 34 ----

First observation is within SK-Gd’s reach!

DSNB events number with 10 years observation


Not only for DSNB

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ν̅e+p

ν+e scattering

(10kpc SN simulation）

ν＋e－→ν＋ｅ－ν̅e ＋ｐ→ｅ++n

If ν̅e can be tagged, directional events (ν+e scattering events) are enhanced. Pointing accuracy should be improved. For 10kpc SN ~5° ~3°(@90%C.L.)

ν̅e w/o tagging ν̅e tagged with 80% eff.

Sensitive to ν̅e of Si burning phase. 800~2000 events/day for pre-supernova at 200pc


EGADS To study the Gd water quality with actual detector materials. The detector fully mimic Super-K detector;

SUS frame, PMT and PMT case, black sheets, etc. Tests for Hyper-K; 13 HPDs

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Evaluating Gadolinium’s Action on Detector Systems200 m3 tank with 240 PMTs

15m3 tank to dissolve Gd

Gd water circulation system(purify water with keeping Gd)

EGADS2014


Water transparency and Gd concentration in EGADS

21

Gd had been dissolved from Nov. 2014 to May. 2015

Pure water

The light left at 15 m in the 200m3

tank was very stable and ~75% for 0.2% Gd2(SO4)3 , which corresponds to ~92% of SK-IV pure water average.

Reached target value in 2015 Apr.

Gd2(SO4)3 concentration is uniform and stable.

Sampling positionTopCenterBottom

2000

1500

1000

500Con

cent

ratio

n(pp

m)

Che

renk

ov li

ght

left

at

15 m

(%

)

Blue band: SK-III and SK-IV values

2014 2015


SK & T2K Joint Statement on “SK-Gd”

22

On June 27, 2015, the Super-Kamiokande collaboration approved the SK-Gd project which will enhance neutrino detectability by dissolving gadolinium in the Super-K water.T2K and SK will jointly develop a protocol to make the decision about when to trigger the SK-Gd project, taking into account the needs of both experiments, including preparation for the refurbishment of the SK tank and readiness of the SK-Gd project, and the T2K schedule including the J-PARC MR power upgrade. Given the currently anticipated schedules, the expected time of the refurbishment is 2018.

Jan.30, 2016


New water system is under construction

23

Current main water system

New Gd water purification system

SK

2016 Apr. 8mx7mx50m

will be in FY2016

Ordered dissolving system and 60t/h circulation system


Conclusion

Only SN1987A so far. Many detectors in the world are waiting for next SN. SK-Gd project tries to catch neutrinos from past SNe. 0.2% of Gd sulfate was dissolved in EGADS test tank and

it was confirmed that there is no showstopper for putting Gd into SK, therefore SK-Gd was accepted by Super-K collaboration in June 2015.

SK & T2K joint statement was made in Jan. 2016 and the SK refurbishment in 2018 is anticipated.

24

We will change! SK evolves into SK-Gd.


Extra slides

25


Relevant processes

26

SNOwGLoBES http://www.phy.duke.edu/~schol/snowglobes/

IBD dominates. <20MeV, electron elastic scatterings can be used.

Water detectors Liquid scintillators


Detectors ready for Supernova

27

Online since

Detector#of events expected for 10kpc SN

Directionality

Baksan 1980 330 ton liquid scintillator ~100 ν̅ep e+n No

LVD 1992 1000 ton liquid scintillator, 840 counters. ~300 ν̅ep e+n No

Super-K 1996 32,000 tons of water target.~7300 ν̅ep e+n, ~300 νeνe

Yes

KamLAND 2002 1000 ton liquid scintillator, single volume. ~300 ν̅ep , ~60 CC on 12C, ~300 νp νp

No

ICECUBE 2005 Gigaton ice target.By coherent increase of PMT single rates.

No

BOREXINO 2007 300 ton liquid scintillator, single volume. ~100 ν̅ep , ~20 CC on 12C, ~100 νp νp

No

HALO 2010 SNO 3He neutron detectors with 76 ton lead target. ~40 No

Daya Bay 2011 20ton x 8, total 160ton liquid scintillator, ~50 ν̅ep No

NOvA 2014 Surface detector. 14kton liquid scintillator. No


Neutron capture signal in EGADS Using Am/Be + BGO

28

[μsec]

Gd concentration dependence was confirmed.

Delayed signal spectrum

DataMC

Time to delayed signal

DataMC

supernova neutrinos in sk-gd and other experiments€¦ · pre-supernova at 200pc hiroyuki sekiya...

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