OBSERVATIONS OF COSMIC NEUTRINOS IN THE KAMIOKANDE II DETECTOR

THE NOBEL PRIZE IN PHYSICS, 2002

Wathan Pratumwan

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The Nobel Prize in Physics, 2002 was concerned about new windows for astronomical observation.

“for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources”

“for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos”

Masatoshi KoshibaRaymond Davis Jr.Ricardo Giacconi

<http://www.nobelprize.org/nobel_prizes/physics/laureates/2002/>

II. Cosmic neutrino sources ‣ The Sun ‣ Supernovae

III. Kamiokande II detectorI. Neutrinos

IV. Observation results ‣ Supernova neutrinos ‣ Solar neutrinos

V. The outlook

COSMIC NEUTRINOS IN THE KAMIOKANDE II DETECTOR

INTRODUCTION | NEUTRINOS

Neutrinos are rarely interact with other matter.4

<https://commons.wikimedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg>

`

Relative strength(two protons in nucleus)

EM interaction = 1weak interaction = 10-7

strong interaction = 20

THE SUN & SUPERNOVAE

COSMIC NEUTRINO SOURCES

<http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2005-14c>

INTRODUCTION | THE SUN

Nuclear fusions in the core energise the Sun and produce neutrinos.

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the standard solar model (SSM) proton-proton chain

1H + 1H → 2H + e+ + νe 1H + e- + 1H → 2H + νe

3He + 1H → 4He + e+ + νe2H + 1H → 3He + γ

3He + 4He → 7Be + γ

7Be + e- → 7Li + νe

3He + 3He → 4He + 21H 7Li + 1H → 4He + 4He

7Be + 1H → 8B + γ

8B → 8Be* + e+ + νe

8Be* → 4He + 4He

pp pep

hep

8B

7Be

ppI ppII

ppIII

99.77% 0.23%

84.92%

25.08%

99.9%

0.1%

10-5%

TEXT 7

INTRODUCTION | SUPERNOVAE

Core-collapse supernovae produce neutrinos which ignite the explosions.

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Neutrino burst (left) and accretion (right) stage of stellar core collapse<http://dx.doi.org/10.1016/j.physrep.2007.02.002>

electron captureelectron capture

pair creation

In a supernova, a star releases >99% of its gravitational binding energy as neutrinos. ~ 1044 J

INTRODUCTION | SUPERNOVAE

Q: Which of the following would be brighter, in terms of the amount of energy delivered to your retina?

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<https://what-if.xkcd.com/73/>

a. A supernova, seen from as far away as the Sun is from the Earth

b. The detonation of a hydrogen bomb pressed against your eyeball?

Ans: a. is brighter by nine orders of magnitude!

Hint: However big you think supernovae are, they're bigger than that.

INTRODUCTION | NEUTRINOS AS A PROBE

Neutrino could travel undisturbedly.10

The structure of the Sun

<https://commons.wikimedia.org/wiki/File:Sun_poster.svg>

Neutrinos

Visible light

KAMIOKANDE II DETECTORNEUTRINO DETECTION

KAMIOKANDE EXPERIMENT | ORIGINAL KAMIOKANDE

KamiokaNDE aimed to search for proton decay.12

<http://www-sk.icrr.u-tokyo.ac.jp/uploads/slide-08.jpg>

‣ KamiokaNDE = Kamioka Nucleon Decay Experiment

‣ It was first designed to search for proton decay by measuring the water Cherenkov radiation.

‣ The experiment was located in a mine under a mountain to reduce backgrounds.

KAMIOKANDE EXPERIMENT | KAMIOKANDE II DETECTOR

Upgraded Kamiokande II aimed to detect solar neutrinos.

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Schematic outline of the Kamiokande II detector

<http://dx.doi.org/10.1103/PhysRevD.38.448>

fiducial volume 2140-ton water

photomultiplier tube (PMT)~20% of total surface of the fiducial volume

anticounter‣ shielding against gamma

rays and neutrons ‣ muon “veto”

‣ Real-time detection ‣ Directional sensitive ‣ Energy threshold of 8.8 MeV

KAMIOKANDE EXPERIMENT | NEUTRINO DETECTION

A neutrino generates a charged particle emitting the Cherenkov radiation.

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left <http://www-sk.icrr.u-tokyo.ac.jp/sk/detector/howtodetect-e.html>right <http://www.ps.uci.edu/~tomba/sk/tscan/compare_mu_e/>

ν + e- → ν + e-ν̅e + p → n + e+

Neutrino… ‣ arrival time ‣ direction ‣ energy

The Cherenkov ring emitted by an electron and detected by PMTs

SUPERNOVA NEUTRINOSOBSERVATION RESULTS

10 days afterBefore

Australian Astronomical Observatory

KAMIOKANDE EXPERIMENT | SUPERNOVA NEUTRINOS

Supernova 1987A was discovered on 24 Feb. 1987.16

SN 1987A‣ Type

‣ Host galaxy

‣ Distance

‣ Discovery

Type II (peculiar)

Large Magellanic Cloud

167,885 light-years

24 Feb. 1987 (23:00 UTC)

KAMIOKANDE EXPERIMENT | SUPERNOVA NEUTRINOS

A neutrino burst was detected on 23 Feb. 1987, 7:35:35 UTC

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A time sequence of events in a 45-sec interval entered on 23 February 1987, 7:35:35 UTC.<http://dx.doi.org/10.1103/PhysRevLett.58.1490>

SOLAR NEUTRINOSOBSERVATION RESULTS

KAMIOKANDE EXPERIMENT | SOLAR NEUTRINOS

The 450-days sample showed an enhancement in the direction of the Sun.

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Distribution in the cosine of the angle between the electron trajectory and the direction of the Sun <http://dx.doi.org/10.1103/PhysRevLett.63.16>

KAMIOKANDE EXPERIMENT | SOLAR NEUTRINOS

The measured 8B neutrino flux is lower than the prediction by the standard solar model.

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KAM-II dataSSM

= 0.46 ± 0.13(stat.)± 0.08(syst.)

Energy distribution of the solar neutrino signal.The histogram is the distribution predicted by SSM.<http://dx.doi.org/10.1103/PhysRevLett.63.16>

The deficiency was consistent with the result from Davis’ experiment.

THE OUTLOOKIMPACTS OF THE KAMIOKANDE II

THE OUTLOOK

Impacts of the Kamiokande II experiment on astronomy, astrophysics and particle physics

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‣ Cherenkov detectors for neutrinos

‣ Neutrino telescopes for neutrino astronomy

‣ Core-collapse mechanism of supernova

‣ Supernova Early Warning System (SNEWS)

‣ The solar neutrino problem ▶︎ neutrino oscillations

SUMMARY

Observations of cosmic neutrinos in the Kamiokande II detector

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a) Solar neutrinos ‣ enhanced in the

direction of the Sun ‣ lower than prediction

b) Supernova neutrinos ‣ high-flux burst signal ‣ arrived before light

detect neutrinos with the water Cherenkov radiation

EXTRA

EXTRA

Stellar evolution

http://www.jpl.nasa.gov/infographics/uploads/infographics/full/10737.jpg

EXTRA

Core-collapse mechanism of supernovae

<http://dx.doi.org/10.1016/j.physrep.2007.02.002>

EXTRA

Supernova neutrino signal modeling

<ArXiv:1507.05613>

EXTRA

Supernova neutrinos

Scatter plot of the detected electron energy and the cosine of the angle between the measured electron direction and the direction of the Large Magellanic Cloud.

<http://dx.doi.org/10.1103/PhysRevD.38.448>

EXTRA

Cherenkov radiation