Takaaki KajitaInstitute for Cosmic Ray Research, The Univ. of Tokyo

104th Indian Science Congress Jan. 3, 2017

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KAGRA

Outline

• Introduction• Kamiokande• Super-Kamiokande• Discovery of atmospheric neutrino oscillations• Contribution to the discovery of solar neutrino oscillations:

Super-Kamiokane and KamLAND• Future neutrino studies• New research in Kamioka: Gravitational waves • Summary

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Introduction

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Where is Kamioka?

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• Neutrinos;• are elementary particles like electrons and

quarks,• have no electric charge,• have, like the other particles, 3 types (flavors),

namely electron-neutrinos (νe), muon-neutrinos (νµ) and tau-neutrinos (ντ),

• are produced in various places, such as the Earth’s atmosphere, ….

• can easily penetrate through the Earth, • can, however, interact with matter very rarely.

• In the very successful Standard Model of particle physics, neutrinos are assumed to have no mass.

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What are neutrinos?

Neutrino @NASA

Neutrino oscillations

Atmospheric Neutrino Oscillations 6

If neutrinos have masses, neutrinos change their flavor (type) from one flavor (type) to the other. For example, νµ could oscillate to ντ.

Probability:νµ to remain νµ

Probability:νµ toντ

Wikipedia

If neutrino mass is smaller, the oscillation length (L/E) gets longer.

L is the neutrino flight length (km),E is the neutrino energy (GeV).

S. Sakata, Z. Maki, M. Nakagawa

Sakata Memorial Archival Library

B. Pontecorvo

Theoretically predicted by;arXiv:0910.1657

Kamiokande

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Elec. room

Water system

Kamioka Nucleon Decay Experiment (Kamiokande)

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In the late 1970’s, Grand Unified Theories of elementary particles were proposed. They predicted that protons and neutrons should decay with the lifetime of about 1030 years. Several proton decay experiments began in the early 1980’s. One of them was Kamiokande.

Kamiokande(3000 ton water tank)

Cherenkov light

Detector wall

Photodetectors

Charged particle

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Construction of the Kamiokande detector (spring 1983)

The Kamiokande experiment started in July 1983.

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Didn’t observe proton decays, but…

Solar neutrinos could be observed.

Improvement of the Kamiokande detector to observe solar neutrinos.

Initial idea of Super-Kamiokande. (both by M. Koshiba)

Kamiokande did not observe proton decays. However, it was found that the detector has a very good performance due to 50 cm diameter photomultiplier tubes that were developed for the Kamiokande experiment.

(photo by Hamamatsu Photonics Co.)

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Toward Kamiokande-II (1984-5)

Construction of the bottom outer detector

Construction of the side outer detector (between the steel tank and the rock)

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SN1987A (Feb. 23, 1987) SN1987A (at LMC)

Num

ber o

f PM

T hi

ts

K. Hirata et al., Phys. Rev. Lett. 58 (1987) 1490.

(The IMB experiment also observed the neutrino signal.)

2002 Nobel prize in Physics to Prof. M. Koshiba

Supernova neutrinos

Atmospheric neutrinos

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© David Fierstein, originally published in Scientific American, August 1999

2 muon-neutrinos 1 electron-

neutrino

INCOMINGCOSMIC RAYS

COSMIC RAY

AIR NUCLEUS

PION

MUONELECTRON

Atmospheric νµ deficit (1980’s to 90’s)

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Kamiokande (1988, 92, 94)

IMB (1991, 92)

Because atmospheric neutrinos are the most serious background to the proton decay searches, it was necessary to understand atmospheric neutrino interactions.

During these studies, a significant deficit of atmospheric νµ events was observed.

Confirmation of solar νe deficit (1989)

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K. S. Hirata et al., Phys. Rev. Lett. 63 (1989) 16.

Solar neutrino data between Jan. 1987 and May 1988:

Standard Solar Model

The Kamiokande results on;• Supernova neutrinos (1987)• Atmospheric neutrino

deficit (1988)• Solar neutrino deficit (1989)were evaluated to be very important.

The construction of the Super-Kamiokande experiment was approved in 1991 by the Japanese government.

Super-Kamiokande

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50,000 ton water Cherenkov detector(22,500 ton fiducial volume)

１０００ｍ underground３９ｍ

４２ｍ

Super-Kamiokande detector

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More than 20 times larger mass

~140 collaborators

Constructing the Super-Kamiokande detector (spring 1995)

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Y. Totsuka

TK

Filling water in Super-Kamiokande

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Jan. 1996

Discovery of atmospheric neutrino oscillations

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Cosmic ray

Long enough to oscillate

Atmospheric neutrinos:What will happen if the νµ deficit is due to neutrino oscillations

Not long enough to oscillate

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A deficit of upward going νµ’s should be observed!

Down-going

Up-going

Prob

abili

ty

(νµ

rem

ain ν µ

)

1 10 100 1000 104L(km) for 1GeV neutrinos

Cosmic ray

Evidence for neutrino oscillations (Super-Kamiokande @Neutrino ’98)

Super-Kamiokande concluded that the observed zenith angle dependent deficit (and the other supporting data) gave evidence for neutrino oscillations.

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Y. Fukuda et al., PRL 81 (1998) 1562

Contribution to the discovery of solar neutrino oscillations:

Super-Kamiokande and KamLAND

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Solar neutrino problem

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J. N. BahcallR. Davis Jr.

600 tonC2Cl4

http://www.astronomynotes.com/starsun/s4.htm

http://www.sns.ias.edu/~jnb/

https://www.bnl.gov/bnlweb/raydavis/

Pioneering Homestake solar neutrino experiment observed only about 1/3 of the predicted solar neutrinos (1960’s). This problem was confirmed by the subsequent experiments in the 1980’s and 90’s.

Solving the solar neutrino problem (2001-2002)

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SNOνe flux

Super-K ES(νe +νµ +ντ

flux)

Flux (106/cm2/sec)

νµ +ντ flux !!

Art McDonald

1000 ton of heavy water (D2O)

SNOνe +νµ +ντflux

SNO

Neutrino oscillation: electron neutrinos to the other neutrinos.

νeDe-pp

νeνe

νDνpn

Photo: K. MacFarlane. Queen's University /SNOLAB

Graph1

SNO2SNO2

スーパーカミオカンデスーパーカミオカンデ

SNO1SNO1

電子ニュートリノ

電子ニュートリノ以外

1.76

3.33

1.76

0.56

1.76

0

Sheet1

電子ニュートリノ デンシ電子ニュートリノ以外 デンシイガイ

SNO21.763.33

スーパーカミオカンデ1.760.56

SNO11.760

グラフのデータ範囲の大きさを変更するには、範囲の右下隅をドラッグしてください。

KamLAND

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1kton liq. scintillator

Many nuclear power stations around KamLAND at the distance of about 180 km. Neutrino osc. experiment with reactor neutrinos.

KamLAND is a 1kton liq. scintillator detector, and was constructed at the location of Kamiokande after its completion.

@ Research center for neutrino science, Tohoku University

Really neutrino oscillations !

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KamLAND PRD 83 (2011) 052002

KamLAND data on neutrino oscillations from nuclear power stations.

Really neutrino oscillations!

Atsuto Suzuki

What have we learned? Why are neutrinos important?

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1st generation

2nd generation

3rd generation

0.01 1 100 104 106 108 1010 1012 1014

Mass（eV/c2）

Charged leptons (electrons, etc.)

Quarks？Neutrinos(with some assumptions)

The neutrino masses are approximately (or more than) 10 billion (10 orders of magnitude) smaller than the corresponding masses of quarks and charged leptons!We believe this is the key to understand the nature at the smallest and the largest scales.

Future neutrino studies

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Neutrino mass

1st generation

2nd generation

3rd generation

0.01 1 100 104 106 108 1010 1012 1014

Mass（eV/c2）

？

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0.01 1 100 104 106 108 1010 1012 1014

Mass（eV/c2）

？

Or

Future experiments that will tell us the order of the neutrino masses

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LBNF/DUNE

KM3NeT/ORCA

PINGUINO

JUNO

RENO-50

RENO-50

Hyper-K

New research in Kamioka: - Gravitational waves

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Researches in Kamioka (2017)

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KAGRA

In 1983, we had only 1 experiment (Kamiokande)

The map of underground Kamiokain 2017 is shown right.

Probably, this development is due to the dynamics of science.

In any case, we have started a new project on gravitational waves in 2010.

A. Einstein predicted gravitational waves in 1916 base on his theory of general relativity.

Image of the gravitational wave emission from a binary black hole system. These back holes merge and a new heavier black hole will be created.

Black hole

Black hole

Gravitational waves

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The first detection of gravitational waves in LIGO (Sep.14, 2015)

2 back holes with the masses of 36 Msun and 29 Msun merged at the distance of 1.3 B light-years. The mass of the newly formed blackhole was 62 Msun. GW energy of 3 Msun equivalent was emitted.

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Red Blue

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KAGRA and its unique features

The detector will be constructed underground Kamioka. Reduction of seismic noise (to approximately 1/100).

Cryogenic mirrors will be used to reduce the thermal noise.

Very high sensitivity.

KAGRA under construction

Polished cryogenic sapphire mirror (23kg).Central room (Nov. 2015)

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KAGRA had its initial operation in 2016, plans the first cryogenic interferometer operation in the spring of 2018, and the high sensitivity run in 2019.

One of the 3km vacuum tubes (Feb 2015)

Virgo

KAGRALIGO

IndIGO/LIGO-India

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International GW network

2LIGO+Virgo 2LIGO+Virgo+LIGO-India+KAGRA

S. Fairhurst, J. Phys. Conf. Ser. 484 (2014) 012007

Summary• “Kamioka” has been contributing a lot to basic science in the last 30

years, and expected to contribute more in the future. • In the early 1980’s, Kamiokande began to observe proton decays.• Kamiokade observed Supernova neutrinos and atmospheric neutrino deficit

and confirmed solar neutrino deficit. These results gave strong motivation to construct Super-Kamiokande.

• In 1998, Super-Kamiokande discovered atmospheric neutrino oscillations. • KamLAND contributed much to the understanding of solar neutrino

oscillations.• KAGRA is a new project trying to observe gravitational wave signals. KAGRA

would like to join the global GW network in a few years.• India is expected to play very important roles in basic science such as

the neutrino and gravitational wave researches. 39

Researches in KamiokaOutlineIntroductionWhere is Kamioka?スライド番号 5Neutrino oscillationsKamiokandeKamioka Nucleon Decay Experiment (Kamiokande) スライド番号 9スライド番号 10スライド番号 11スライド番号 12Atmospheric neutrinosAtmospheric nm deficit (1980’s to 90’s) Confirmation of solar ne deficit (1989)Super-KamiokandeSuper-Kamiokande detectorConstructing the Super-Kamiokande detector (spring 1995)Filling water in Super-Kamiokande Discovery of atmospheric neutrino oscillationsAtmospheric neutrinos:�What will happen if the nm deficit is due to neutrino oscillations Evidence for neutrino oscillations (Super-Kamiokande @Neutrino ’98)Contribution to the discovery of solar neutrino oscillations: � Super-Kamiokande and KamLAND Solar neutrino problemSolving the solar neutrino problem (2001-2002)KamLANDReally neutrino oscillations !What have we learned? �Why are neutrinos important? Future neutrino studiesNeutrino mass Future experiments that will tell us the order of the neutrino masses New research in Kamioka: � - Gravitational waves Researches in Kamioka (2017)Gravitational waves The first detection of gravitational waves in LIGO (Sep.14, 2015)KAGRA and its unique features KAGRA under constructionInternational GW networkSummaryBack up