[damocles]

Hi Johann

In reply to your latest:
Neutrinos are usually detected and characterized via the discrepancy in momentum in the patterns of those tracks of collisions you refer to. The neutrinos themselves never produce tracks; they are always the "leftover" that is required to balance the picture.

The carbon tetrachloride method did and does work, though the first few times it was tried produced inconclusive results.

There is a good web page at University of Wisconsin
http://icecube.wisc.edu/info/neutrinos
that provides reliable summary answers to a lot of your questions.

I would suggest that you check the CERN website for the detail of how they are investigating neutrinos at present.

[Johann Mahne]

Neutrinos probably do have a tiny mass because it is important that they do or they could not oscillate between the three different types electron, muon and tau.

I will add to your answer though that the electron mass in your units must be about 0.5 MeV/c^2 , which is at least 2 million times that of a neutrino

  If a neutrino has such a low mass, how could it transform to a much heavier particle?
Is a neutrino considered to be a "elementary particle"?

[imatfaal]

Neutrinos probably do have a tiny mass because it is important that they do or they could not oscillate between the three different types electron, muon and tau.

I will add to your answer though that the electron mass in your units must be about 0.5 MeV/c^2 , which is at least 2 million times that of a neutrino

  If a neutrino has such a low mass, how could it transform to a much heavier particle?
Is a neutrino considered to be a "elementary particle"?

The transformation (more properly thought of as an oscillation) is not from neutrino to electron or other heavy particle - it is between the three flavours of neutrino the electron neutrino ν_e the mu neutrino ν_μ and the tau neutrino ν_τ.  It was calculated through quantum mechanics that a ν_e has a non-zero probability of being a ν_μby the time it arrives somewhere else (and so on for the other flavour changes).  The masses of the three flavours of neutrino are indeed different and very complicated as they are in fact mass expectation values and we can only at present measure the difference between the different flavour masses.

The three flavours of neutrino are indeed considered at elementary have a look at the diagram at bottom this page at Stanford - you will see the neutrinos shown above the big brother leptons from which the flavours take their name. 

[Johann Mahne]

Hi Imatfaal,
Thanks for the link. Also to Damocles.
 Which neutrino "flavours" are in action at CERN. Is it right to assume that more massive types are detected at lower velocities?
  Under what conditions are the three different types produced?
 SoulSurfer was talking about the decay of a neutron into a proton electron and neutrino. What flavour occurs in this case?

[imatfaal]

Johann - this is the quantum mechanical world, and nothing is simple.  There is not really any point talking about a particle as simply a tau neutrino; it is a particle with a probability of being a ν_τ, but it also has a finite probability of being a ν_e or a ν_μ.  But when you detect a neutrino you either get a ν_τ, a ν_e, or a ν_μ - but before that it is a superposition of all three.

When you detect a neutrino using a huge amount of water (super-k) you are are basically on the lookout for what is called Cherenkov radiation.  Cherenkov radiation is the light given off when a charged particle travels through a medium (not a vacuum) faster than the local speed of light!  Now this has nothing to do with the recent Gran Sasso claim - but rather the fact that light travels through media other than the vacuum at below c.  Highly energetic particles can travel through this medium quicker than light (but still less that c). 

When a neutrino actually interacts with something in these huge water baths (vanishingly small probability) it produces a charged particle which is really moving quickly - so much so it will be going quicker than light does in water.  This charged particle will give off cherenkov radiation which is detected by photomultipliers arranged around the edges. 

If the neutrino that interacts is currently a mu-neutrino you will get a high speed muon formed, an electron-neutrino will form an electron, a tau-neutrino...  The tau and the muon (the big leptons not the neutrinos) decay rapidly into unique showers of other particles (most of which are high-speed) the electron bashes into a water molecule.  The particle showers of the tau and the muon and the single spark of the electron produce very different patterns of cherenkov radiation - so the detector will know which flavour the neutrino was when it interacted.

in beta^- decay a neutron -> a proton an election and a neutrino.  In this case the flavour is electron but it is in fact an anti-neutrino.  as neutrinos have no charge it is possible they are their own anti-particle but the quantum chromodynamics only really works out if the particle emitted is an antimatter version.  in positron emission (ie PET scan) a proton -> nuetron a positron and a electron-neutrino. 
 

hope that is not too confusing

[imatfaal]

Hi Imatfaal,
Thanks for the link. Also to Damocles.
 Which neutrino "flavours" are in action at CERN.

Johann

Didn't notice this bit.  CERN/OPERA Gran Sasso was set up to look at the oscillations of neutrinos that we were talking about above.  CERN was able to use a proton beam striking a graphite wall to produce a beam of mesons that with a little filtering and magnetic channelling would end up decaying and producing a beam of almost solely mu-neutrinos.  This beam of ν_μ was directed at Gran Sasso ~730km away.  Gran Sasso was set up to detect ν_τ however - and it was hoped that accurate measurements of the change and probabilities of oscillation could be made.  I haven't read up on the Gran Sasso detectors (lotsa lead and photo-multipliers) so I cannot say if they were only detecting ν_τ - but I presume they must have been able to either measure only ν_τ or differentiate ν_τ from ν_μ and ν_e for their experiment to work

[Johann Mahne]

I hate to agree with everybody above but SSurfers comments on spin are spot on.  This is a cut-off point where you can no longer think classically - the electron cannot be seen as a little globe spinning on its axis; if it was the surface would be travelling at a velocity above c.  Spin is an intrinsic property - which is testable,predictable, and closely connect to angular momentum ; but it is not a little particle spinning like a top

Stephen Hawkins says that if a particle has for example a spin of 0 then it always "looks the same" from all directions
If it has a spin of 2, it "looks the same" for every 180 degrees of rotation.
  Is he talking about the electrostatic or magnetic fields that "look the same", or something else?
How is this spin related to angular momentum?

[imatfaal]

I hate to agree with everybody above but SSurfers comments on spin are spot on.  This is a cut-off point where you can no longer think classically - the electron cannot be seen as a little globe spinning on its axis; if it was the surface would be travelling at a velocity above c.  Spin is an intrinsic property - which is testable,predictable, and closely connect to angular momentum ; but it is not a little particle spinning like a top

Stephen Hawkins says that if a particle has for example a spin of 0 then it always "looks the same" from all directions
If it has a spin of 2, it "looks the same" for every 180 degrees of rotation.
  Is he talking about the electrostatic or magnetic fields that "look the same", or something else?
How is this spin related to angular momentum?

Stephen Hawking is a great scientist and mathematician - and I wouldn't and couldn't criticise his work; but his popularizations can be a bit odd.  He will quite happily give a great and accessible explanation for a incredibly difficult concept (which I will lap up and feel I understand) and then a few paragraphs later say that the explanation was of""heuristic value only" ie not really true. 

I do not know if this is one of those occasions but I suspect it is.  Spin is an intrinsic and basic property of fundamental particles - and like the other ones it is very hard to get to the nitty-gritty of what it actually is!

A good start is Wikipedia's page Spin(physics)

[acsinuk]

Spin and current loops are interlinked magnetically.  But how can 3D current loop spin or frequency be linked into the standard model? CliveS

[GlentoranMark]

I listened to this Podcast yesterday, perhaps it may be of use to the OP and others.

http://www.bbc.co.uk/programmes/b0106tjc

Melvyn Bragg and his guests discuss the neutrino.

In 1930 the physicist Wolfgang Pauli proposed the existence of an as-yet undiscovered subatomic particle. He also bet his colleagues a case of champagne that it would never be detected. He lost his bet when in 1956 the particle, now known as the neutrino, was first observed in an American nuclear reactor.

Neutrinos are some of the most mysterious particles in the Universe. The Sun produces trillions of them every second, and they constantly bombard the Earth and everything on it. Neutrinos can pass through solid rock, and even stars, at almost the speed of light without being impeded, and are almost impossible to detect. Today, experiments involving neutrinos are providing insights into the nature of matter, the contents of the Universe and the processes deep inside stars.

With:

Frank Close
Professor of Physics at Exeter College at the University of Oxford

Susan Cartwright
Senior Lecturer in Particle Physics and Astrophysics at the University of Sheffield

David Wark
Professor of Particle Physics at Imperial College, London, and the Rutherford Appleton Laboratory.

Producer: Thomas Morris.

[Johann Mahne]

Thanks for all the excellent links.
This is the re formatted link of Imatfaal
http://en.wikipedia.org/wiki/Spin_%28physics%29

[imatfaal]

Thanks Johann - I had a curly instead of a square bracket

Have modified the original