Kamiokande = Kamioka Nucleon Decay Experiment SUPER -KAMIOKANDE Kamiokande = Kamioka Nucleon Decay Experiment

Topics of Discussion Detector Super-Kamiokande Solar neutrinos Results

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

Photomultplier Tube

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

Cherenkov radiation Cherenkovlight wavefront 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

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. Explanation of color-bar remains to be done.

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

Time of neutrino’s arrival It is possible to search for day/night or seasonal variations

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

Estimate of neutrino Energy It is possible to distinguish neutrinos from different reaction chains in the sun So, where and how are neutrinos produced?

Solar fusion 1 Basic process in sun and most stars – fusion of hydrogen(protons) into helium First step is combination of two protons 11H + 11H  21H + e+ + e p ne n then e

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 + 11H  32H + 

Solar fusion 3 In our sun 3He is most likely to react with another 3He nucleus. 32He + 32He  42He + 2 11H +  The complete process is given by: 4 11H  42He +2 e+ +2 e + This process is known as the proton-proton cycle or the ‘PPI chain’.

Solar fusion 4 PPII : 32He + 42He  74Be +  74Be + e- 73Li + e 73Li + 11H 2 42He PPIII: 32He + 42He  74Be +  74Be + 11H  84Be + e+ + e 84Be  2 42He

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

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

Solar neutrinos at S-K Super Kamiokande uses elastic scattering of neutrinos from electrons Cherenkov radiation emitted by the electron is detected  e

Overview ne e

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

Theory versus experiment

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

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

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.

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

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