Cosmic Ray Research in Japan and Osaka City University

Takaaki KajitaInstitute for Cosmic Ray Research, The University of Tokyo

International Symposium in Honor of Professor Nambufor the 10th Anniversary of his Nobel Prize in Physics

Dec. 12, 2018

Outline

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• Introduction• Present cosmic ray research: 1) Neutrinos

Appendix: Neutrino oscillations• Present cosmic ray research: 2) Very high energy cosmic rays• Present cosmic ray research: 3) Gravitational waves• Summary

Many thanks to Prof. Kanda for providing me a report on “Cosmic Ray Institute” of the Osaka City University.

Introduction

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History of 2 “Cosmic Ray Institutes” in Japan after World War II

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year1949 “Norikura Cosmic Ray Observatory” at the Norikura Mountain by Prof. Y. Watase

(Osaka City Univ., OCU) 1950 “Asahi Hut” at the Norikura Mountain supported by Asahi Academic Grant (of

Asahi News Paper) 1950 “Underground cosmic ray observatory” at Yaizu (OCU)1952 “Cosmic Ray Institute” at OCU1953 “Cosmic Ray Observatory (Norikura Observatory)” of the Univ. of Tokyo (UToyko)

1956 “Norikura Cosmic Ray Observatory” of OCU was closed1956 Cosmic Ray Division of the Institute for Nuclear Studies (INS, UTokyo) 1961 “Underground cosmic ray observatory” moved to Mitsuishi from Yaizu (OCU) 1976 “Institute for Cosmic Ray Research” of UTokyo (based on Norikura Observatory

and Cosmic Ray Division of INS)

Norikura Observatory

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“Asahi Hut” (around 1950, from a book on Prof. Minagawa)

Norikura Observatory (ICRR) (in the 1950’s?)

Cosmic Ray Research in OCU and Prof. Nambu

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An article in Japanese science magazine “自然” by Minoru Oda (Nov. 1978):……. 実験のグループには理論家が横にいなければ、という強い信念を（渡瀬譲は）もっていた。批判者としての理論家、少なくとも理論的雰囲気がないと型にはまった技術万能主義になったり、頑固にいつまでもつづけるしかしようがない実験になってしまう、というのである。…….こういうことから、素粒子論グループをつくることを小竹（理工学部長）に説いて実現している。…...早川幸男（当時気象研）、山口嘉夫、西島和彦（東大理学部）、阪大から中野薫夫を採ることにし、その上に教授として南部陽一郎（東大理学部）を置くことにした。……

……, (Yuzuru Watase, leader of the cosmic ray group OCU) had a strong belief that there should be theorists next to the groups of experimentalists. Theorists are required as critics. At least, without a theoretical atmosphere, the groups might become too technology oriented, or might continue experiments without any reasons.Therefore, Y. Watase persuaded Kotake (Dean) to form a group of theoretical particle physics. …. He decided to hire Sachio Hayakawa, Yoshio Yamaguchi, Kazuhiko Nishijima and Tadao Nakano. Finally, he decided to hire Yoichiro Nambu as the professor of this group. ….

Present cosmic ray research in Japan

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• Present cosmic ray research: 1) NeutrinosAppendix: neutrino oscillations

• Present cosmic ray research: 2) Very high energy cosmic rays• Present cosmic ray research: 3) Gravitational waves

Present cosmic ray research: 1) Neutrinos

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Discovery of atmospheric neutrinos (1965)

In South Africa F. Reines et al., PRL 15, 429 (1965)

In IndiaC.V. Achar et al., PL 18, 196 (1965)

OCU (Hinotani and Miyake)

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In 1965, atmospheric neutrinos were observed for the first time by detectors located very deep underground.

Photo by H.Sbel Photo by N. Mondal

Kamioka Nucleon Decay Experiment (Kamiokande)

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In the 1970’s, Grand Unified Theories were proposed. These theories predicted that protons and neutrons (i.e., nucleons) should decay with the lifetime of about 1030 years.

Several proton decay experiments began in the early 1980’s. One of them was the KGFexperiment lead by Prof. Saburo Miyake and people in OCU. The other was Kamiokande.

Cherenkov light

Detectorwall

Photodetectors

Charged particle

Electronics/computer

Water system

Kamiokande(3000 ton water Cherenkov detector)

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Kamiokande construction team (Spring 1983)

Y. TotsukaM. Koshiba(2002 Nobel Prize) T. Kifune

M. Takita

M. NakahataTK

K. Arisaka A. Suzuki T.Suda

Kamiokande

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The experiment began in July 1983.

Message from Prof. Nambu

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On Nov. 16, 1984, Professor Nambu visited Kamiokande. Unfortunately, we have no photo of him…. However, in Kamiokande, we ask visitors to leave a message.

So we should observe a proton decay before 2084…

AfterBefore

Supernova SN1987A

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Feb. 1987（LMC, 160,000 light-years)

Birth of neutrino astronomy

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Total 24 neutrino events observed by 3 detectorson Feb. 23, 1987;

Understood the basic mechanism of the supernova explosion!

Prof. M. Koshiba(Cultural Medal 1997,Nobel prize 2002)

IMB-3(8 events)

Baksan(5 events)

Kamiokande-II(11 events)

Birth of neutrino astronomy

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Fax from Prof. Nambu to Prof. Koshiba, when Prof Koshiba received the Cultural Medal in 1997.

“Wanted to be a physicist”

The present neutrino detector: Super-Kamiokande (50,500 ton)

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Exploring the history of Supernova explosion

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todaytime

Super-Kamiokande collab. would like to observe neutrinosproduced by the Supernova explosion in the past Universe!

Birth of the Universe

Credit: NASA/WMAP Science Team

Super-K

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Detecting Supernova relic neutrinos

10 12 14 16 18 20 22 24 26 28Position Energy (MeV)

Expected spectrum in SK-GD

2.5σ4.3σ2.1σ

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

σ: 10 years with SK-Gd

Total BG

0 0 0.02 0.20

102030405060708090

100

Gadolinium sulfate concentration [%]

Ca

ptu

re o

n g

ad

olin

ium

[%

]

Gd capture eff.

0 0.002 0.02 0.20

20

40

60

80

100[%]

0.2% Gd2(SO4)3 （~100t for SK）gives 90% neutron capture

Gadolinium sulfate concentration[%]

(M. Ikeda, neutrino 2018)νe + p e+ + n ,

n + Gd Gd + γ’s (total E of γ’s ~8MeV)

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Status and plans

July 2018 End of Aug., 2018Super-K will resume the data taking in Jan. 2019.Probably, Super-K-Gd with Gd (0.02%) will begin in late 2019 (or early 2020).Super-K-Gd with Gd (0.2%) will begin in 202X.

Appendix: Neutrino oscillations

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Atmospheric neutrinos

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

2 muon-neutrinos 1 electron-

neutrino

Incoming cosmic rays

Cosmic ray

Air nucleus

PionMuon

Electron

The Kamiokande and IMB experiments observed the deficit of atmospheric neutrinos in the late 1980’s to early 1990’s. No one understood why.

Super-Kamiokande µ-neutrinoτ-neutrino

Evidence for neutrino oscillations (Neutrino Conference in 1998)

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

Solar neutrino oscillation (2001-2002)

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SNOνe flux

Super-K ES(νe +νµ +ντ

flux)

Flux (106/cm2/sec)

νµ +ντ flux !!

1000 ton of heavy water (D2O)

SNOνe +νµ +ντflux

νeDe-pp

νeνe

νDνpn

SK, PRL 86 (2001) 5651SNO PRL 89 (2002) 011301SNO PRC 72, 055502 (2005)

+ Accelerator based long baseline neutrino oscillation experiments (K2K and T2K). Nakaya-san.

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。

Hyper-K as a natural extension of water Ch. detectors

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Kamiokande & IMBNeutrinos from SN1987A Atmospheric neutrino deficitSolar neutrino (Kam)

Super-KAtmospheric neutrino oscillation Solar neutrino oscillation with SNOFar detector for K2K and T2K

Hyper-K

Present cosmic ray research: 2) Very highenergy cosmic rays

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109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021

Energy (electron volt, eV)

Cosm

ic-r

ay fl

ux

Highest-energy cosmic rays

~1020eV

102

10-1

10-4

10-7

10-10

10-13

10-16

10-19

10-22

10-25

10-28

Cosmic ray fluxHow cosmic rays of 1020 eV are generated?orWhat are the most powerful accelerators generating cosmic rays of 1020 eV?

1020 eV cosmic rays do not come from the very far Universe (~< 50Mpc), due to the interaction of cosmic ray and cosmic microwave background radiation.

1020 eV cosmic rays are not bent much by the galactic and inter-galactic magnetic fields.

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How can we detect 1020 eV cosmic rays?

Simulation of a very high energy cosmic ray in the atmosphere

Fluorescence detectordetects air fluorescenceLight from air shower

Surface detectordirectly observes penetratingsecondary particles at the surface

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Telescope Array (TA) experiment (Utah, USA)

Surface Detectors (SD)507 plastic scintillator SDs

1.2 km spacing~700 km2

Fluorescence Detectors (FD)

3 stations

Maininstitutions in Japan: OCU and ICRR.Main persons in OCU: Profs. Ogio (photo) and Tsunesada

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Telescope Array (TA) site

TA surface detector

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Cosmic ray arrival direction

With 25° oversampling, Maximum pre-trial significance: ~5σ

at RA=144.3o, Dec=+40.3o

Observed: 34Expected : 13.5

Post-trial significance : 3σ

The data show an interesting excess at a particular direction!

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The next stage…

Telescope Array needs more data. x4 improvement in the surface area

(3000 km2, the “TAx4” project)

We really look forward to seeing new results from Telescope Array!

Present cosmic ray research: 3) Gravitationalwaves

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Introduction

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LIGO Scientific Collaboration and Virgo Collaboration, PRL, 116, 061102 (2016)

Press Conference at NSF on Feb. 11, 2016

And many subsequent observations.Congratulations to LIGO and Virgo!

Common goals of ground based GW detectors

Merger of binary neutronstarsWe want to understand

the origin of the heavy metals in the Universe (more accurately).

…

Merger of binaryblackholes How the blackholes

were created? …

Supernova explosion How the heavy stars

finish their life? ….

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Virgo

KAGRALIGO

LIGO-India

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global map of GW detectors

In operation Under Construction Project approved

The world GW community works together to know the details (e.g., sources) of GWs.

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KAGRA gravitational wave detector

Maininstitutions in Japan: OCU NAOJ, KEK, and ICRR.Main persons in OCU: Profs. Kanda (photo) and Itoh

KAGRA 3km x 3km arms

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Connection and the leak tests of 3km X 3km beam tubes have been finished in Feb. 2015.

Toward the detection of GWs in KAGRA

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KAGRA plans the first operation in late 2019.

Installation of the first cryogenic mirror（Nov.30, 2017）

Preparation of cryogenic mirror atthe University of Toyama.

（22cm (diameter), 15cm (thick), 23kg） To the KAGRA site

Summary• The field of cosmic rays had significant progresses. Groups in OCU

and various institutions in Japan have been playing very important roles in these progresses.

• We are in the era of “multi-messenger astronomy”: neutrinos, cosmic rays and gravitational waves play very important roles.

• Please stay tuned.

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Cosmic Ray Research in Japan and Osaka City UniversityOutlineIntroduction�History of 2 “Cosmic Ray Institutes” in Japan after World War II Norikura ObservatoryCosmic Ray Research in OCU and Prof. NambuPresent cosmic ray research in JapanPresent cosmic ray research: 1) Neutrinos�Discovery of atmospheric neutrinos (1965) Kamioka Nucleon Decay Experiment (Kamiokande) スライド番号 11Kamiokande Message from Prof. Nambu Supernova SN1987ABirth of neutrino astronomy Birth of neutrino astronomy The present neutrino detector: Super-Kamiokande (50,500 ton)Exploring the history of Supernova explosionスライド番号 19スライド番号 20Appendix: Neutrino oscillationsAtmospheric neutrinosEvidence for neutrino oscillations (Neutrino Conference in 1998)Solar neutrino oscillation (2001-2002)Hyper-K as a natural extension of water Ch. detectors Present cosmic ray research: 2) Very high energy cosmic rays�Cosmic ray fluxHow can we detect 1020 eV cosmic rays?Telescope Array (TA) experiment (Utah, USA)Telescope Array (TA) siteCosmic ray arrival direction The next stage…Present cosmic ray research: 3) Gravitational waves�IntroductionCommon goals of ground based GW detectors global map of GW detectorsKAGRA gravitational wave detector KAGRA 3km x 3km armsToward the detection of GWs in KAGRASummaryスライド番号 41超新星爆発の予感？Toward the detection of past Supernova neutrinos in Super-K超新星残骸での宇宙線加速Expected observation of Supernova neutrinos in Super-KExample of very high energy gamma ray telescopesAt the center of a Supernova remnantImportance of Global GW Network: Angular resolutionAnother big news (GW170817)Center area Not easy to detect GWsHow can we know the cosmic acceSupernova explosion