Understanding Neutrino Detectors & All-Neutrino Detection

[bbbl67]

Now my understanding of neutrino detectors is that there are two common fluids used in the detectors, either Tetrachloroethylene (C2Cl4) aka "dry-cleaning fluid", and heavy water (D20). Why were these substances chosen specifically? Is there something about the elements within these substances that make them easier to study vs. any other element on the periodic table?

Also within these two substances, only one of the elements in each is singled out for study. In the case of C2Cl4, it is the Chlorine that is studied, and not the Carbon. In the heavy water, it is the Deuterium that is studied and not the Oxygen. Why is that? Isn't a neutrino just as likely to hit the Carbon or the Oxygen atoms, in each case?

Now, a related question. Is the Sudbury Neutrino Observatory (SNO) the only one in the world that can detect all neutrino events, and not just electron-neutrino events, or are there others now? SNO uses heavy water, is heavy water better for all-neutrino detection vs. C2Cl4? According to the following article, under the section about Cerenkov radiation:

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html

According to the above, a muon-neutrino strike maintains a very well-defined light-cone, whereas an electron-neutrino strike results in an electron shower which produces a very diffuse light-cone. Why should there be an electron shower from a single electron-neutrino hit, while a muon-neutrino hit doesn't result in a muon shower? Aren't each neutrino strike just producing one electron or one muon, respectively? Why should there even be a shower of electrons, when only one new electron is produced?

 

[Orodruin]

Now my understanding of neutrino detectors is that there are two common fluids used in the detectors, either Tetrachloroethylene (C2Cl4) aka "dry-cleaning fluid", and heavy water (D20).

No, these are only two choices that have been used historically. Other choices include regular water (eg, Super-K), liquid scintillator (eg, LSND, NOvA), iron (eg, INO), and emulsions (eg, OPERA).

Also within these two substances, only one of the elements in each is singled out for study. In the case of C2Cl4, it is the Chlorine that is studied, and not the Carbon. In the heavy water, it is the Deuterium that is studied and not the Oxygen. Why is that? Isn't a neutrino just as likely to hit the Carbon or the Oxygen atoms, in each case?

This is a matter of how the detection process works and how the physics allows the neutrinos in study to react with the different elements.

In the chlorine case, the search was for solar neutrinos and the interactions with chlorine left a particular residual atom that could be searched for. In the case of the deuterium in the SNO detector, it was because it allowed for the study of a particular interaction that has the same strength regardless of the neutrino flavour.

Is the Sudbury Neutrino Observatory (SNO) the only one in the world that can detect all neutrino events, and not just electron-neutrino events, or are there others now? SNO uses heavy water, is heavy water better for all-neutrino detection vs. C2Cl4?

SNO is decommissioned and therefore no longer operational. Any other water Cherenkov detector will also be sensitive to other neutrino flavours, but not as strongly as to electron neutrinos (the cross section is about 1/6th for other flavours). For the neutral current process in SNO, all flavours interact with equal strength. Furthermore, for the charged current process in SNO, only electron neutrinos were relevant. The chlorine experiments were based on inverse beta decay and therefore only sensitive to electron neutrinos.

Aren't each neutrino strike just producing one electron or one muon, respectively? Why should there even be a shower of electrons, when only one new electron is produced?

Yes, the neutrino strikes a single electron. The shower is a result from the subsequent electron interactions.

 

[jtbell]

Other choices include regular water (eg, Super-K), liquid scintillator (eg, LSND, NOvA), iron (eg, INO), and emulsions (eg, OPERA).

As well as liquid hydrogen, and a liquid hydrogen/neon mixture (in the http://history.fnal.gov/neutrino.html#15); and halon (CF₃Br, in the Gargamelle bubble chamber at CERN).

 

[bbbl67]

No, these are only two choices that have been used historically. Other choices include regular water (eg, Super-K), liquid scintillator (eg, LSND, NOvA), iron (eg, INO), and emulsions (eg, OPERA).

What is liquid scintillator exactly?

In the case of iron, is that just solid iron, or is it molten?

This is a matter of how the detection process works and how the physics allows the neutrinos in study to react with the different elements.


In the chlorine case, the search was for solar neutrinos and the interactions with chlorine left a particular residual atom that could be searched for. In the case of the deuterium in the SNO detector, it was because it allowed for the study of a particular interaction that has the same strength regardless of the neutrino flavour.

Understood, but why exactly were certain elements within the molecules excluded? In the case of dry-cleaning fluid, it was the carbons that were ignored. In the case of water, it was the oxygens that were ignored.

Yes, the neutrino strikes a single electron. The shower is a result from the subsequent electron interactions.

Okay, so I can understand a hgh-speed electron smashing through a cloud of other electrons and causiong havoc That's because electrons all have the same charge, and other electrons want to get away from it. However, muons also have the same charge as electrons. Why wouldn't a high-speed muon also crash through a cloud of elecctrons and create a shower of electrons too?

 

[Orodruin]

What is liquid scintillator exactly?

https://en.wikipedia.org/wiki/Scintillator

In the case of iron, is that just solid iron, or is it molten?

Why on Earth would you use molten iron?

Understood, but why exactly were certain elements within the molecules excluded

I already told you this. They do not participate in reactions that are detectable.

However, muons also have the same charge as electrons.

The charge is not the important parameter. The mass plays a huge role and the muon is 200 times more massive. You should be able to find this described in any basic text on how particles interact with a medium.

 

[ChrisVer]

That's because electrons all have the same charge, and other electrons want to get away from it.

Not only (I guess you are referring to electron scattering off other electrons)...
there is Brehmstrahlung radiation (gammas) from the electron which produces e+e- pairs...then they also interact with other electrons and can give further photons and electron/positron pairs. The whole thing ends up to an electromagnetic shower.
The power radiated away by a particle with Brehmstrahlung radiation depends on the particle's mass- and so the electrons tend to radiate away more energy than muons...
Why are you studying neutrino detectors?

 

[bbbl67]

Not only (I guess you are referring to electron scattering off other electrons)...
there is Brehmstrahlung radiation (gammas) from the electron which produces e+e- pairs...then they also interact with other electrons and can give further photons and electron/positron pairs. The whole thing ends up to an electromagnetic shower.
The power radiated away by a particle with Brehmstrahlung radiation depends on the particle's mass- and so the electrons tend to radiate away more energy than muons...

So a less massive particle, radiates away more power than a more massive one? I guess I already should've known that, as taking a proton through a circular particle accelerator doesn't result in much Brehmstrahlung radiation, but doing the same thing to an electron does. Is there some formula that shows this relationship between generated Brehmstrahlung and mass?

Why are you studying neutrino detectors?

I'm not really sure anymore, I guess curiosity really. I think I was just reading about something else, and that got me off on a tangent towards neutrino detectors. Often happens with me, I got a million questions saved up inside me, and I usually forget most of them, and then every once in a while, one comes back to the forefront and I got to figure it out completely, before I forget it again.

Oh, BTW, I just remembered what led me to it. Somebody recently asked me something about the Weak Force, and the functional differences between the W & Z bosons, especially the Z. That then led to my sudden curiosity about neutrinos again, since they are involved in so many of the transformations caused by the Weak. I'm not a physicist, just a layman: I got a background in engineering, but not particle physics.

 

[ChrisVer]

Is there some formula that shows this relationship between generated Brehmstrahlung and mass?

simply:
https://en.wikipedia.org/wiki/Bremsstrahlung#Total_radiated_power

 

[bbbl67]

simply:
https://en.wikipedia.org/wiki/Bremsstrahlung#Total_radiated_power

Perfect, thanks! Interestingly, there seems to be a recurring theme in many areas of physics which seem to show that a lower-mass object seems to lose more energy than a higher mass object, for example, smaller black holes lose more energy due to Hawking Radiation than larger ones.

 

[ChrisVer]

Well the mass powers don't coincide...

 

[mfb]

Bremsstrahlung, from German "bremsen" (brake) and "strahlung" (radiation). No h in "brems", two s.

I guess I already should've known that, as taking a proton through a circular particle accelerator doesn't result in much Brehmstrahlung radiation, but doing the same thing to an electron does.

This is not bremsstrahlung, it is synchrotron radiation.

The interaction of charged particles with matter or electromagnetic fields mainly depends on the speed, for high-energetic particles expressed as the Lorentz factor ##\gamma##. To reach the same gamma-factor, protons need a factor 2000 more energy than electrons, muons need a factor 200 more. That is rarely the case, so electrons are typically the fastest particles around, which also means they lose the most energy.

This has nothing to do with Hawking radiation.

 

[bbbl67]

Bremsstrahlung, from German "bremsen" (brake) and "strahlung" (radiation). No h in "brems", two s.This is not bremsstrahlung, it is synchrotron radiation.

Okie-dokie.

The interaction of charged particles with matter or electromagnetic fields mainly depends on the speed, for high-energetic particles expressed as the Lorentz factor ##\gamma##. To reach the same gamma-factor, protons need a factor 2000 more energy than electrons, muons need a factor 200 more. That is rarely the case, so electrons are typically the fastest particles around, which also means they lose the most energy.

So, it's caused by Relativistic speeds?

This has nothing to do with Hawking radiation.

Well obviously not, it's just an interesting observation. Perhaps a coincidence, that's all.

 

[mfb]

So, it's caused by Relativistic speeds?

Yes, all the effects discussed are negligible or don't happen at nonrelativistic speeds.