observations of cosmic neutrinos in the kamiokande ii detector
TRANSCRIPT
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%
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 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
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>
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 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
Core-collapse mechanism of supernovae
<http://dx.doi.org/10.1016/j.physrep.2007.02.002>
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>