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SUPER -KAMIOKANDE

Kamiokande = Kamioka Nucleon Decay Experiment

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Topics of Discussion

Detector Super-Kamiokande Solar neutrinos Results

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Properties of Super-K A Large Water Cherenkov Detector

for Cosmic Particles Size: Cylinder of 41.4m (Height) x

39,9m (Diameter) Weight: 50,000 tons of pure Water Number of Photomultipier Tubes:

11,200

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Photomultplier Tube

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How does S-K detect?

The PMTs collect the pale blue light called Cherenkov light which is emitted by particles travelling faster as light in the water

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v

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nvsin 0cc

v

1

nvsin 0cc

c0 = speed of light in vacuum

Cherenkovlight

wavefront

Compare : shock wave of supersonic airplanes

See http://webphysics.davidson.edu/applets/applets.html for a nice illustration

Cherenkov radiation

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The picture above shows an incoming 1063 MeV neutrino which strikes a free proton at rest and produces a 1032 MeV muon. Different colors are related to time, blue shows the muon, green the electron of the muon decay.

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Advantages of S-K The direction the neutrino came

from can be determined The time of the neutrino’s arrival

can be determined The energy of the electron gives a

rough estimate of the neutrino energy

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Time of neutrino’s arrival

It is possible to search for day/night or seasonal variations

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Direction of neutrino

One can provide solid evidence that the neutrinos are actually coming from the sun

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Estimate of neutrino Energy

It is possible to distinguish neutrinos from different reaction chains in the sun

So, where and how are neutrinos produced?

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Solar fusion 1 Basic process in sun and most stars –

fusion of hydrogen(protons) into helium

First step is combination of two protons

11H + 1

1H 21H + e+ + e

p

e

e

then

n

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Solar fusion 2

The cross-section for this process is very small at average proton energies in the core of the sun, however there is a huge number of protons available to react.

Deuterons so produced fuse with protons:

21H + 1

1H 32H +

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Solar fusion 3 In our sun 3He is most likely to react

with another 3He nucleus. 3

2He + 32He 4

2He + 2 11H +

The complete process is given by: 4 1

1H 42He +2 e+ +2 e +

This process is known as the proton-proton cycle or the ‘PPI chain’.

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Solar fusion 4 PPII : 3

2He + 42He 7

4Be +

74Be + e- 7

3Li + e

73Li + 1

1H 2 42He

PPIII: 32He + 4

2He 74Be +

74Be + 1

1H 84Be + e+ + e

84Be 2 4

2He

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Solar neutrinos

Neutrinos are ‘ghost ‘-particles which merely interact, they are the only known type of particle that can escape from the sun’s core bringing direct information about the solar interior

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Solar neutrinos 2 Neutrinos are difficult to detect

and measure Neutrinos produced in different

branches carry away different amounts of energy and momentum – detector design has to take account

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Solar neutrinos at S-K Super Kamiokande uses elastic

scattering of neutrinos from electrons

Cherenkov radiation emitted by the electron is detected

e

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Overview

e

e

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http://www.pc.uci.edu/~tomba/sk/tscan/solar

http://www.pc.uci.edu/~tomba/sk/tscan/solar

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Theory versus experiment

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All five blue bars, according to various experiments, show significantly less values than the model predictions: the discrepancy is approximately a factor of two

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Additional Result of S-K S-K observes a significant difference

between the numbers of neutrinos coming up through the ground as went down on the other side

A possible explanation is neutrino conversion takes place in matter – called Mikheyev-Smirnov-Wolfenstein effect

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Additional Result of S-K Super-K has found evidence of the

transformation of muon type neutrinos to something else, probabely tau type neutrinos (neutrino oscillations).

This is taken as strong evidence that neutrinos have a small, but finite mass.

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What This Means

Neutrino oscillations is today the most promising of the proposed solutions to the solar neutrino problem

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Solar neutrino research was

undertaken to test stellar evolution Unexpectedly one found evidence

for new neutrino physics More experiments are needed to

understand neutrino oscillation phenomena